Co-reporter:Jiyeon Kim, Tomi Iivonen, Jani Hämäläinen, Marianna Kemell, Kristoffer Meinander, Kenichiro Mizohata, Lidong Wang, Jyrki Räisänen, Radim Beranek, Markku Leskelä, and Anjana Devi
Chemistry of Materials July 25, 2017 Volume 29(Issue 14) pp:5796-5796
Publication Date(Web):June 28, 2017
DOI:10.1021/acs.chemmater.6b05346
We have developed a low-temperature atomic layer deposition (ALD) process for depositing crystalline and phase pure spinel cobalt oxide (Co3O4) films at 120 °C using [Co(tBu2DAD)2] and ozone as coreagent. X-ray diffraction, UV–vis spectroscopy, atomic force microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis were performed to characterize the structure and properties of the films. The as-deposited Co3O4 films are crystalline with a low amount of impurities (<2% C and <5% H) despite low deposition temperatures. Deposition of Co3O4 onto thin TiO2 photoanodes (100 nm) for water oxidation resulted in 30% improvement of photocurrent (after 10 ALD cycles yielding small Co3O4 particles) as compared to pristine TiO2 films), and exhibited no detrimental effects on photocurrent response up to 300 deposition cycles (approximately 35 nm thick films), demonstrating the applicability of the developed ALD process for deposition of effective catalyst particles and layers in photoelectrochemical water-splitting devices.
Co-reporter:Andrian P. Milanov, Roland A. Fischer and Anjana Devi
Inorganic Chemistry December 1, 2008 Volume 47(Issue 23) pp:11405-11416
Publication Date(Web):November 6, 2008
DOI:10.1021/ic801432b
Eight novel homoleptic tris-guanidinato complexes M[(NiPr)2CNR2]3 [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), iPr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The iPr-Me2N-guanidinates of Y, Gd and Dy (1a−c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the iPr-Me2N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that iPr-Me2N-guanidinates of Y, Gd and Dy (1a−c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd2O3 and Dy2O3 thin films on Si(100) substrates. The MOCVD grown films of Gd2O3 and Dy2O3 were highly oriented in the cubic phase, while the ALD grown films were amorphous.
Co-reporter:Daniel Peeters;Alexer Sadlo;Katarina Lowjaga;Oliver Mendoza Reyes;Lidong Wang;Lukas Mai;Maximilian Gebhard;Detlef Rogalla;Hans-Werner Becker;Ignacio Giner;Guido Grundmeier;Dariusz Mitoraj;Markus Grafen;Andreas Ostendorf;Radim Beranek
Advanced Materials Interfaces 2017 Volume 4(Issue 18) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/admi.201700155
Vapor phase deposited iron oxide nanostructures are promising for fabrication of solid state chemical sensors, photoelectrodes for solar water splitting, batteries, and logic devices. The deposition of iron oxide via chemical vapor deposition (CVD) or atomic layer deposition (ALD) under mild conditions necessitates a precursor that comprises good volatility, stability, and reactivity. Here, a versatile iron precursor, namely [bis(N-isopropylketoiminate) iron(II)], which possesses ideal characteristics both for low-temperature CVD and water-assisted ALD processes, is reported. The films are thoroughly investigated toward phase, composition, and morphology. As-deposited ALD grown Fe2O3 layers are amorphous, while the CVD process in the presence of oxygen leads to polycrystalline hematite layers. The nanostructured iron oxide grown via CVD consists of nanoplatelets that are appealing for photoelectrochemical applications. Preliminary tests of the photoelectrocatalytic activity of CVD-grown Fe2O3 layers show photocurrent densities up to 0.3 mA cm−2 at 1.2 V versus reversible hydrogen electrode (RHE) and 1.2 mA cm−2 at 1.6 V versus RHE under simulated sunlight (1 sun). Surface modification by cobalt oxyhydroxide (Co-Pi) co-catalyst is found to have a highly beneficial effect on photocurrent, leading to maximum monochromatic quantum efficiencies of 10% at 400 nm and 4% at 500 nm at 1.5 V versus RHE.
Co-reporter:M. Gebhard;M. Hellwig;A. Kroll;D. Rogalla;M. Winter;B. Mallick;A. Ludwig;M. Wiesing;A. D. Wieck;G. Grundmeier;A. Devi
Dalton Transactions 2017 vol. 46(Issue 31) pp:10220-10231
Publication Date(Web):2017/08/08
DOI:10.1039/C7DT01280B
For the first time, synthesis of two new amidinate-ligand comprising heteroleptic indium complexes, namely [InCl(amd)2] (1) and [InMe(amd)2] (2), via salt-metathesis and their detailed characterization is reported. For comparison, the earlier reported homoleptic tris-amidinate [In(amd)3] (3) was also synthesized and analyzed in detail especially with respect to the thermal properties and molecular crystal structure analysis which are reported here for the first time. From nuclear magnetic resonance spectroscopy (NMR) and single-crystal X-ray diffraction (XRD), all three compounds were found to be monomeric with C2 (compound 1 and 2) and C3 symmetry (compound 3). Both halide-free compounds 2 and 3 were evaluated regarding their thermal properties using temperature-dependent 1H-NMR, thermogravimetric analysis (TGA) and iso-TGA, revealing suitable volatility and thermal stability for their application as potential precursors for chemical vapor phase thin film deposition methods. Indeed, metalorganic chemical vapor deposition (MOCVD) experiments over a broad temperature range (400 °C–700 °C) revealed the suitability of these two compounds to fabricate In2O3 thin films in the presence of oxygen on Si, thermally grown SiO2 and fused silica substrates. The as-deposited thin films were characterized in terms of their crystallinity via X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM) and composition through complementary techniques such as Rutherford-backscattering spectrometry (RBS) in combination with nuclear reaction analysis (NRA) and X-ray photoelectron spectroscopy (XPS). From UV/Vis spectroscopy, the deposited In2O3 thin films on fused silica substrates were found to be highly transparent (T > 95% at 560 nm, compound 3). In addition, Hall measurements revealed high charge carrier densities of 1.8 × 1020 cm−3 (2) and 6.5 × 1019 cm−3 (3) with a Hall-mobility of 48 cm2 V−1 s−1 (2) and 74 cm2 V−1 s−1 (3) for the respective thin films, rendering the obtained thin films applicable as a transparent conducting oxide that could be suitable for optoelectronic applications.
Co-reporter:Sarah Karle;Detlef Rogalla;Arne Ludwig;Hans-Werner Becker;Andreas Dirk Wieck;Markus Grafen;Andreas Ostendorf
Dalton Transactions 2017 vol. 46(Issue 8) pp:2670-2679
Publication Date(Web):2017/02/21
DOI:10.1039/C6DT04399B
Novel copper ketoiminate compounds were synthesized and for the first time applied for additive-free solution-based deposition of nanoscale copper oxide thin films. The two closely related compounds, namely the bis[4-(2-ethoxyethyl-imino)-3-pentanonato]copper, [Cu(EEKI)2], and bis[4-(3-methoxypropylimino)-3-pentanonato]copper, [Cu(MPKI)2], were characterized by means of elemental and thermogravimetric analysis (TGA), as well as electron impact mass spectrometry (EI-MS). The advantages of these compounds are that they are liquid and possess excellent solubility in common organic solvents in addition to an optimum reactivity towards ambient moisture that enables a facile solution-based approach to nanoscale copper oxide thin films. Moreover, no additives or aging is needed to stabilize the solution processing of the copper oxide layers. [Cu(MPKI)2] was tested in detail for the deposition of copper oxide thin films by spin coating. Upon one-step annealing, high-quality, uniform, crystalline copper oxide thin films were deposited on Si, SiO2, as well as on quartz substrates. Structural, morphological and compositional characteristics of the copper oxide nanostructures were investigated in detail by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and a combined analysis using Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA). It was possible to control the copper oxide phases (CuO and Cu2O) by systematic tuning of the post-deposition annealing conditions. The functional properties in terms of optical band gap were investigated using UV/Vis spectroscopy, while the transport properties, such as resistivity, mobility and carrier concentration were analyzed employing Hall measurements, which confirmed the p-type conductivity of the copper oxide layers.
Co-reporter:Richard O'Donoghue;Julian Rechmann;Morteza Aghaee;Detlef Rogalla;Hans-Werner Becker;Mariadriana Creatore;Andreas Dirk Wieck
Dalton Transactions 2017 vol. 46(Issue 47) pp:16551-16561
Publication Date(Web):2017/12/06
DOI:10.1039/C7DT03427J
Herein we describe an efficient low temperature (60–160 °C) plasma enhanced atomic layer deposition (PEALD) process for gallium oxide (Ga2O3) thin films using hexakis(dimethylamido)digallium [Ga(NMe2)3]2 with oxygen (O2) plasma on Si(100). The use of O2 plasma was found to have a significant improvement on the growth rate and deposition temperature when compared to former Ga2O3 processes. The process yielded the second highest growth rates (1.5 Å per cycle) in terms of Ga2O3 ALD and the lowest temperature to date for the ALD growth of Ga2O3 and typical ALD characteristics were determined. From in situ quartz crystal microbalance (QCM) studies and ex situ ellipsometry measurements, it was deduced that the process is initially substrate-inhibited. Complementary analytical techniques were employed to investigate the crystallinity (grazing-incidence X-ray diffraction), composition (Rutherford backscattering analysis/nuclear reaction analysis/X-ray photoelectron spectroscopy), morphology (X-ray reflectivity/atomic force microscopy) which revealed the formation of amorphous, homogeneous and nearly stoichiometric Ga2O3 thin films of high purity (carbon and nitrogen <2 at.%) under optimised process conditions. Tauc plots obtained via UV-Vis spectroscopy yielded a band gap of 4.9 eV and the transmittance values were more than 80%. Upon annealing at 1000 °C, the transformation to oxygen rich polycrystalline β-gallium oxide took place, which also resulted in the densification and roughening of the layer, accompanied by a slight reduction in the band gap. This work outlines a fast and efficient method for the low temperature ALD growth of Ga2O3 thin films and provides the means to deposit Ga2O3 upon thermally sensitive polymers like polyethylene terephthalate.
Co-reporter:Lukas Mai;Zivile Giedraityte;Marcel Schmidt
Journal of Materials Science 2017 Volume 52( Issue 11) pp:6216-6224
Publication Date(Web):2017 June
DOI:10.1007/s10853-017-0855-6
Luminescent erbium-based inorganic–organic hybrid materials play an important role in many frontier nano-sized applications, such as amplifiers, detectors and OLEDs. Here, we demonstrate the possibility to fabricate high-quality thin films comprising both erbium and an appropriate organic molecule as a luminescence sensitizer utilizing the combined atomic layer deposition and molecular layer deposition (ALD/MLD) technique. We employ tris(N,N′-diisopropyl-2-dimethylamido guanidinato)erbium(III) [Er(DPDMG)3] together with 3,5-pyridine dicarboxylic acid as precursors. With the appreciably high film deposition rate achieved (6.4 Å cycle−1), the guanidinate precursor indeed appears as an interesting new addition to the ALD/MLD precursor variety toward novel materials. Our erbium–organic thin films showed highly promising UV absorption properties and a photoluminescence at 1535 nm for a 325-nm excitation, relevant to possible future luminescence applications.
Co-reporter:M. Gebhard, F. Mitschker, M. Wiesing, I. Giner, B. Torun, T. de los Arcos, P. Awakowicz, G. Grundmeier and A. Devi
Journal of Materials Chemistry A 2016 vol. 4(Issue 5) pp:1057-1065
Publication Date(Web):11 Jan 2016
DOI:10.1039/C5TC03385C
An efficient plasma-enhanced atomic layer deposition (PE-ALD) process was developed for TiO2 thin films of high quality, using a new Ti-precursor, namely tris(dimethylamido)-(dimethylamino-2-propanolato)titanium(IV) (TDMADT). The five-coordinated titanium complex is volatile, thermally stable and reactive, making it a potential precursor for ALD and PE-ALD processes. Process optimization was performed with respect to plasma pulse length and reactive gas flow rate. Besides an ALD window, the application of the new compound was investigated using in situ quartz-crystal microbalance (QCM) to monitor surface saturation and growth per cycle (GPC). The new PE-ALD process is demonstrated to be an efficient procedure to deposit stoichiometric titanium dioxide thin films under optimized process conditions with deposition temperatures as low as 60 °C. Thin films deposited on Si(100) and polyethylene-terephthalate (PET) exhibit a low RMS roughness of about 0.22 nm. In addition, proof-of-principle studies on TiO2 thin films deposited on PET show promising results in terms of barrier performance with oxygen transmission rates (OTR) found to be as low as 0.12 cm3 × cm−2 × day−1 for 14 nm thin films.
Co-reporter:Sarah Karle;Van-Son Dang;Marina Prenzel;Detlef Rogalla;Hans-Werner Becker
Chemical Vapor Deposition 2015 Volume 21( Issue 10-11-12) pp:335-342
Publication Date(Web):
DOI:10.1002/cvde.201507189
Thin films of Y2O3 are deposited on Si(100) and Al2O3 (0001) substrates via metal-organic (MO)CVD for the first time using two closely related yttrium tris-amidinate compounds as precursors in the presence of oxygen in the temperature range 400–700 °C. The structural, morphological, and compositional features of the films are investigated in detail. At deposition temperatures of 500 °C and higher both the precursors yield polycrystalline Y2O3 thin films in the cubic phase. The compositional analysis revealed the formation of nearly stoichiometric Y2O3. The optical band gaps are estimated using UV-Vis spectroscopy. Preliminary electrical measurements are performed in the form of a metal oxide semiconductor (MOS) structure of Al/Y2O3/p-Si/Ag. Leakage currents and dielectric constants are also determined.
Co-reporter:Manish Banerjee, Rüdiger W. Seidel, Manuela Winter, Hans-Werner Becker, Detlef Rogalla and Anjana Devi
Dalton Transactions 2014 vol. 43(Issue 6) pp:2384-2396
Publication Date(Web):08 Nov 2013
DOI:10.1039/C3DT52335G
Treatment of tetrakis(diethylamido)zirconium(IV); [Zr(NEt2)4] with a series of β-ketoimines ({[RHN]C(CH3)C(H)C(CH3)O} where R is a functionalized side-chain; 4-(2-methoxyethylamino)pent-3-en-2-one, Hmeap; 4-(3-methoxypropylamino)pent-3-en-2-one, Hmpap; 4-(2-(dimethylamino)ethylamino)pent-3-en-2-one, Hdeap; 4-(3-(dimethylamino)propylamino)pent-3-en-2-one, Hdpap) leads to an amine substitution reaction that yielded novel monomeric heteroleptic mixed amido-ketoiminato complexes of the type bis(4-(2-methoxyethylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (1), bis(4-(3-methoxypropylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (2), and bis(4-(3-(dimethylamino)propylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (3), and eight-coordinated homoleptic complexes tetrakis(4-(2-methoxyethylamino)pent-3-en-2-onato)zirconium(IV) (4) and tetrakis(4-(2-(dimethylamino)ethylamino)pent-3-en-2-onato)zirconium(IV) (5), depending on the ratio of the ligand to zirconium. Adopting a similar strategy with zirconium alkoxide, namely [Zr(OiPr)4·iPrOH], with β-ketoimine Hmeap, leads to the formation of a dimer, bis(μ2-isopropoxo)bis(4-(2-methoxyethylamino)pent-3-en-2-onato)tetrakis(isopropoxo)dizirconium(IV) (6). The newly synthesised complexes were characterized by NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, elemental analysis and thermal analysis. The low decomposition temperature facilitated by the stepwise elimination of the ketominate ligand from the complex and the stability of the complexes obtained in air as well as in solution makes them highly suitable for solution based processing of ZrO2 thin films, which is demonstrated using compound 5 on Si(100) substrates. High quality ZrO2 films were obtained and were investigated for their structure, morphology, composition and optical properties. Low temperature crystallisation of ZrO2 is achieved by a simple chemical deposition process using the new class of Zr precursors and the films exhibit an optical transmittance above 90%.
Co-reporter:Manish Banerjee;Van-Son Dang;Michal Bledowski;Radim Beranek;Hans-Werner Becker;Detlef Rogalla;Eugen Edengeiser;Martina Havenith;Andreas D. Wieck
Chemical Vapor Deposition 2014 Volume 20( Issue 7-8-9) pp:224-233
Publication Date(Web):
DOI:10.1002/cvde.201407125
A new heteroleptic titanium precursor with a mixed oxygen/nitrogen coordination sphere [Ti(dmap)2(NMe2)2] (Hdmap = 1–dimethylamino–2–propanol) is synthesized by a simple elimination reaction on tetrakis–dimethylaminotitanium(IV) [Ti(NMe2)4]. The compound shows encouraging results in terms of chemical and thermal stability compared to the parent alkyl amide [Ti(NMe2)4], and is therefore more suitable for MOCVD applications. TiO2 thin films are grown on Si(100) and ITO-coated borosilicate glass substrates via MOCVD in the temperature range 500–800°C. The deposition temperature has a significant effect on the phase and microstructure of the TiO2 films obtained, which influences the functional properties. The optical bandgaps of the films are in the range 2.92–3.36 eV. The best photocurrent response (1.5 mA cm−2 under AM 1.5G conditions) in aqueous electrolytes is observed for films grown at 700°C having improved crystallinity and porous columnar structure.
Co-reporter:Anjana Devi;W. M. M. (Erwin) Kessels
Chemical Vapor Deposition 2014 Volume 20( Issue 7-8-9) pp:186-188
Publication Date(Web):
DOI:10.1002/cvde.201477896
No abstract is available for this article.
Co-reporter:Anjana Devi
Coordination Chemistry Reviews 2013 Volume 257(23–24) pp:3332-3384
Publication Date(Web):December 2013
DOI:10.1016/j.ccr.2013.07.025
•Progress in precursor chemistry at the Inorganic Materials Chemistry group in Bochum reported.•New classes of MOCVD and ALD precursors developed for group IV and rare earth oxides.•Promising group IV alkoxide and amide based complexes successfully evaluated as precursors.•Novel rare earth complexes with malonates, guanidinates and amidinates as ligands.•Guanidinate complexes have evolved as bench mark precursors for MOCVD and ALD.The concept of the transformation of molecules to materials has been well established in the field of chemical vapor deposition (CVD) and atomic layer deposition (ALD). However, materials scientists are always on the lookout for new materials with enhanced functionalities for eventual application in devices. New materials have become an integral part of modern day technology especially in the field of microelectronics and optoelectronics. The importance of CVD and ALD processes for high throughput and coating on complex device geometries is well recognized for these applications. Since the underlying precursor chemistry is one of the main parameters that dictate these processes, there is still scope for further exploratory research, in terms of precursor design and development that suits the demands of advanced technologies. A wide range of precursors can be used to realize specific class of materials but the trend recently has been driven by the reduced thermal budget needed especially for components employed in microelectronics and optoelectronics. The chronological developments in precursors for CVD/ALD point out that, designer precursors are set to play a major role in the field of materials engineering. The desirable growth conditions could be achieved with a proper selection of compounds which may stem from the available class of metal complexes or even engineered compounds. In this review article, the concept of utilizing ‘old chemistries’ for new CVD and ALD applications will be highlighted focussing on some representative functional materials namely group IV and rare earth oxides. Some of the very recent results on precursor development carried out in the Inorganic Materials Chemistry research group at Bochum, Germany are summarized.
Co-reporter:Ke Xu, Ayan Roy Chaudhuri, Harish Parala, Dominik Schwendt, Teresa de los Arcos, H. Jörg Osten and Anjana Devi
Journal of Materials Chemistry A 2013 vol. 1(Issue 25) pp:3939-3946
Publication Date(Web):17 Apr 2013
DOI:10.1039/C3TC30401A
For the first time, the combination of the homoleptic erbium tris-guanidinate metalorganic complex ([Er(NMe2-Guan)3]) simply with water yielded high quality Er2O3 thin films on Si(100) substrates employing the atomic layer deposition (ALD) process. The process optimization to grow good quality Er2O3 layers was performed by varying the Er precursor pulse time, water pulse time and purge time. The high reactivity of the Er compound towards water and good thermal stability in the temperature range of 150–275 °C (ALD window) resulted in homogeneous, stoichiometric Er2O3 layers with high growth rates (1.1 Å per cycle) and the as-deposited films crystallized in the cubic phase. The saturation behavior at different temperatures in the ALD window and the linear dependence of film thickness as a function of precursor pulse time confirmed the true ALD process. The potential of Er2O3 thin films as gate dielectrics was verified by performing capacitance–voltage (C–V) and current–voltage (I–V) measurements. Dielectric constants estimated from the accumulation capacitance were found to be in the range of 10–13 for layers of different thicknesses (15–30 nm).
Co-reporter:Michael Krasnopolski ; Cristian G. Hrib ; Rüdiger W. Seidel ; Manuela Winter ; Hans-Werner Becker ; Detlef Rogalla ; Roland A. Fischer ; Frank T. Edelmann
Inorganic Chemistry 2013 Volume 52(Issue 1) pp:286-296
Publication Date(Web):December 11, 2012
DOI:10.1021/ic301826s
Five new homoleptic gadolinium tris-amidinate complexes are reported, which were synthesized via the salt-elimination reaction of GdCl3 with 3 equiv of lithiated symmetric and asymmetric amidinates at ambient temperature. The Gd-tris-amidinates [Gd{(NiPr)2CR}3] [R = Me (1), Et (2), tBu (3), nBu (4)] and [Gd{(NEt)(NtBu)CMe}3] (5) are solids at room temperature and sublime at temperatures of about 125 °C (6 × 10–2 mbar) with the exception of compound 4, which is a viscous liquid at room temperature. According to X-ray diffraction analysis of 3 and 5 as representative examples of the series, the complexes adopt a distorted octahedral structure in the solid state. Mass spectrometric (MS) data confirmed the monomeric structure in the gas phase, and high-resolution MS allowed the identification of characteristic fragments, such as [{(NiPr)2CR}GdCH3]+ and [{(NiPr)2CR}GdNH]+. The alkyl substitution patterns of the amidinate ligands clearly show an influence on the thermal properties, and specifically, the introduction of the asymmetric carbodiimide leads to a lowering of the onset of volatilization and decomposition. Compound 5, which is the first Gd complex with an asymmetric amidinate ligand system to be reported, was, therefore, tested for the MOCVD of GdN thin films. The as-deposited GdN films were capped with Cu in a subsequent MOCVD process to prevent postdeposition oxidation of the films. Cubic GdN on Si(100) substrates with a preferred orientation in the (200) direction were grown at 750 °C under an ammonia atmosphere and exhibited a columnar morphology and low levels of C or O impurities according to scanning electron microscopy, Rutherford backscattering, and nuclear reaction analysis.
Co-reporter:Sun Ja Kim;Ke Xu;Harish Parala;Radim Beranek;Michal Bledowski;Kirill Sliozberg;Hans-Werner Becker;Detlef Rogalla;Davide Barreca;Chiara Maccato;Cinzia Sada;Wolfgang Schuhmann;Rol A. Fischer
Chemical Vapor Deposition 2013 Volume 19( Issue 1-3) pp:45-52
Publication Date(Web):
DOI:10.1002/cvde.201206996
Abstract
N-doped titanium dioxide (TiO2) thin films are grown on Si(100) and indium tin oxide (ITO)-coated borosilicate glass substrates by metal-organic (MO)CVD. The intrinsic doping of TiO2 thin films is achieved using all-nitrogen-coordinated Ti precursors in the presence of oxygen. The titanium amide-guanidinate complex, [Ti(NMe2)3(guan)] (guan = N,N′-diisopropyl-2-dimethylamidoguanidinato) has been developed to compensate for the thermal instability of the parent alkylamide [Ti(NMe2)4]. Both of these amide-based compounds are tested and compared as precursors for intrinsically N-doped TiO2 at various deposition temperatures in the absence of additional N sources. The structure and morphology of TiO2 thin films are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Rutherford back scattering (RBS), nuclear reaction analysis (NRA), and secondary ion mass spectrometry (SIMS) analyses are performed to determine N content and distribution in the films. The optical and photoelectrochemical properties of TiO2 thin films on ITO substrates are also examined. N-doped TiO2 thin films, grown from [Ti(NMe2)3(guan)] at 600 °C, exhibit the lowest optical absorption edge (3.0 eV) and the highest visible light photocurrent response. When compared to undoped TiO2, while in UV light photoconversion efficiency decreases significantly, the intrinsically N-doped TiO2 shows enhanced photocurrents under visible light irradiation.
Co-reporter:N.B. Srinivasan, T.B. Thiede, T. de los Arcos, V. Gwildies, M. Krasnopolski, H.-W. Becker, D. Rogalla, A. Devi, R.A. Fischer
Surface and Coatings Technology 2013 230() pp: 130-136
Publication Date(Web):
DOI:10.1016/j.surfcoat.2013.06.024
Co-reporter:Ke Xu, Ramdurai Ranjith, Apurba Laha, Harish Parala, Andrian P. Milanov, Roland A. Fischer, Eberhard Bugiel, Jürgen Feydt, Stefan Irsen, Teodor Toader, Claudia Bock, Detlef Rogalla, Hans-Jörg Osten, Ulrich Kunze, and Anjana Devi
Chemistry of Materials 2012 Volume 24(Issue 4) pp:651
Publication Date(Web):February 10, 2012
DOI:10.1021/cm2020862
Gd2O3 and Dy2O3 thin films were grown by atomic layer deposition (ALD) on Si(100) substrates using the homoleptic rare earth guanidinate based precursors, namely, tris(N,N′-diisopropyl-2-dimethylamido-guanidinato)gadolinium(III) [Gd(DPDMG)3] (1) and tris(N,N′-diisopropyl-2-dimethylamido-guanidinato)dysprosium(III) [Dy(DPDMG)3] (2), respectively. Both complexes are volatile and exhibit high reactivity and good thermal stability, which are ideal characteristics of a good ALD precursor. Thin Gd2O3 and Dy2O3 layers were grown by ALD, where the precursors were used in combination with water as a reactant at reduced pressure at the substrate temperature ranging from 150 °C to 350 °C. A constant growth per cycle (GPC) of 1.1 Å was obtained at deposition temperatures between 175 and 275 °C for Gd2O3, and in the case of Dy2O3, a GPC of 1.0 Å was obtained at 200–275 °C. The self-limiting ALD growth characteristics and the saturation behavior of the precursors were confirmed at substrate temperatures of 225 and 250 °C within the ALD window for both Gd2O3 and Dy2O3. Thin films were structurally characterized by grazing incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses for crystallinity and morphology. The chemical composition of the layer was examined by Rutherford backscattering (RBS) analysis and Auger electron spectroscopy (AES) depth profile measurements. The electrical properties of the ALD grown layers were analyzed by capacitance–voltage (C–V) and current–voltage (I–V) measurements. Upon subjection to a forming gas treatment, the ALD grown layers show promising dielectric behavior, with no hysteresis and reduced interface trap densities, thus revealing the potential of these layers as high-k oxide for application in complementary metal oxide semiconductor based devices.Keywords: atomic layer deposition; electrical properties; morphology; rare earth oxides; structure;
Co-reporter:Manish Banerjee, Nagendra Babu Srinivasan, Huaizhi Zhu, Sun Ja Kim, Ke Xu, Manuela Winter, Hans-Werner Becker, Detlef Rogalla, Teresa de los Arcos, Daniela Bekermann, Davide Barreca, Roland A. Fischer, and Anjana Devi
Crystal Growth & Design 2012 Volume 12(Issue 10) pp:5079
Publication Date(Web):September 6, 2012
DOI:10.1021/cg3010147
The application of new zirconium precursors for the fabrication of ZrO2 and ZrN thin films by metalorganic chemical vapor deposition (MOCVD) is presented. The all-nitrogen coordinated Zr precursors exhibit improved thermal properties for vapor phase fabrication of thin films. The growth of ZrO2 thin films was realized by the combination of the Zr complex with oxygen, while the formation of ZrN thin films was achieved for the first time employing a single source precursor (SSP) approach. This was enabled by the presence of nitrogen containing ligands which contributes to the formation of the ZrN phase without the need for any additional nitrogen source in contrast to classical film growth processes for ZrN thin films. In the first step the newly developed precursors were evaluated thoroughly for their use in MOCVD applications, and in the next step they were utilized for the growth of ZrO2 and ZrN thin films on Si(100) substrates. Polycrystalline ZrO2 films that crystallized in the monoclinic phase and the fcc-ZrN films oriented in the (200) direction were obtained, and their structure, morphology, and composition were analyzed by a series of techniques. This work shows the potential of tuning precursors for vapor phase fabrication of Zr containing thin films with a goal of obtaining two different classes of material systems (ZrO2 and ZrN) using one common precursor.
Co-reporter:Andrian P. Milanov, Ke Xu, Stefan Cwik, Harish Parala, Teresa de los Arcos, Hans-Werner Becker, Detlef Rogalla, Richard Cross, Shashi Paul and Anjana Devi
Dalton Transactions 2012 vol. 41(Issue 45) pp:13936-13947
Publication Date(Web):04 Sep 2012
DOI:10.1039/C2DT31219K
Alternative novel precursor chemistries for the vapor phase deposition of rare-earth (RE) oxide thin films were developed by synthesising the homoleptic guanidinate compounds tris(N,N′-diisopropyl-2-dimethylamidoguanidinato)-scandium(III) [Sc(DPDMG)3] (1), tris(N,N′-diisopropyl-2-dimethylamidoguanidinato)-erbium(III), [Er(DPDMG)3] (2) and tris(N,N′-diisopropyl-2-dimethylamidoguanidinato)-yttrium(III), [Y(DPDMG)3] (3). All three compounds are monomeric as revealed by single crystal X-ray diffraction (XRD) analysis, nuclear magnetic resonance (NMR) and electron impact mass spectrometry (EI-MS). The thermal analysis revealed that the compounds are volatile and very stable under evaporation conditions. Therefore the complexes were evaluated as precursors for the growth of Sc2O3, Er2O3 and Y2O3 thin films, respectively, by metal–organic chemical vapor deposition (MOCVD). Uniform Sc2O3, Er2O3 and Y2O3 films on Si(100) substrates with reproducible quality were grown by MOCVD by the combination of the respective guanidinate precursors and oxygen in the temperature range 350–700 °C. The structural, morphological, compositional and electrical properties of the films were investigated in detail. The most relevant film properties are highlighted in relation to the distinct advantages of the novel precursor chemistries in comparison to the commonly used literature known RE precursors. This study shows that compounds 1–3 are very good precursors for MOCVD yielding Sc2O3, Er2O3 and Y2O3 thin films which are stoichiometric and display suitable electrical properties for their potential use as high dielectric constant (high-k) materials.
Co-reporter:Ke Xu;Andrian P. Milanov;Harish Parala;Christian Wenger;Canan Baristiran-Kaynak;Kaoutar Lakribssi;Teodor Toader;Claudia Bock;Detlef Rogalla;Hans-Werner Becker;Ulrich Kunze
Chemical Vapor Deposition 2012 Volume 18( Issue 1-3) pp:27-35
Publication Date(Web):
DOI:10.1002/cvde.201106934
Abstract
The application of a heteroleptic hafnium amide-guanidinate precursor for the deposition of HfO2 thin films via a water-assisted atomic layer deposition (ALD) process is demonstrated for the first time. HfO2 films are grown in the temperature range 100–300 °C using the compound [Hf(NMe2)2(NMe2-Guan)2] (1). This compound shows self-limiting ALD-type growth characteristics with growth rates of the order of 1.0–1.2 Å per cycle in the temperature range 100–225 °C. The saturation behavior and a linear dependence on film thickness as a function of number of cycles are verified at various temperatures within the ALD window. The as-deposited HfO2 films are characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), and electrical measurements. For a direct comparison of the precursor performance with that of the parent alkyl amide [Hf(NMe2)4] (2), ALD experiments are also performed employing compound 2 under similar process conditions, and in this case no typical ALD characteristics are observed.
Co-reporter:Teresa de los Arcos, Stefan Cwik, Andrian P. Milanov, Vanessa Gwildies, Harish Parala, Tristan Wagner, Alexander Birkner, Detlef Rogalla, Hans-Werner Becker, Jörg Winter, Alfred Ludwig, Roland A. Fischer, Anjana Devi
Thin Solid Films 2012 Volume 522() pp:11-16
Publication Date(Web):1 November 2012
DOI:10.1016/j.tsf.2011.12.007
The growth of tungsten oxide (WO3) based thin films was achieved via metalorganic chemical vapor deposition using an all-nitrogen coordinated tungsten precursor in combination with oxygen. Film growth was performed on Si(100) substrates in the temperature range of 400–800 °C. Employing multi-technique approaches like X-ray diffraction, scanning electron microscopy, atomic force microscopy, Rutherford back scattering, nuclear reaction analysis and X-ray photoelectron spectroscopy, the variation of the growth characteristics and film properties with deposition temperature were studied in terms of crystallinity, structure, surface roughness and composition. Special attention was devoted to the investigation of variations in the film composition for the as-deposited and annealed films.
Co-reporter:Anjana Devi, Stefan Cwik, Ke Xu, Andrian P. Milanov, Heshmat Noei, Yuemin Wang, Davide Barreca, Jan Meijer, Detlef Rogalla, Divine Kahn, Richard Cross, Harish Parala, Shashi Paul
Thin Solid Films 2012 Volume 520(Issue 14) pp:4512-4517
Publication Date(Web):1 May 2012
DOI:10.1016/j.tsf.2011.10.141
Thin films of HfGdOx and HfDyOx were deposited by metalorganic chemical vapor deposition (MOCVD) utilizing guanidinate precursors for Hf, Gd and Dy. The close match in the thermal properties of the precursors enabled the MOCVD of rare-earth (RE) substituted HfO2 over a wide temperature window. Film deposition was carried out in the temperature range 300–700 °C in the presence of oxygen on Si(100) substrates. HfGdOx films were analyzed in detail for their structure, composition and morphology using X-ray diffraction, Rutherford backscattering spectrometry, proton induced X-ray emission, X-ray photoelectron spectroscopy and scanning electron microscopy. The electrical properties of HfGdOx in terms of capacitance–voltage and current–voltage characteristics of metal-insulator-semiconductor device structures were evaluated.
Co-reporter:Tobias B. Thiede, Michael Krasnopolski, Andrian P. Milanov, Teresa de los Arcos, Andreas Ney, Hans-Werner Becker, Detlef Rogalla, Jörg Winter, Anjana Devi, and Roland A. Fischer
Chemistry of Materials 2011 Volume 23(Issue 6) pp:1430
Publication Date(Web):February 24, 2011
DOI:10.1021/cm102840v
Metal−organic chemical vapor deposition (MOCVD) of thin films of two representative rare-earth nitrides is reported here for the first time. Four homoleptic, all-nitrogen-coordinated, rare-earth (RE) complexes were evaluated as precursors for the respective nitride thin film materials. Two guanidinato complexes [RE{(iPrN)2C(NMe2)}3] [RE = Gd (1), Dy (2)] and two amidinato complexes [RE{(iPrN)2CMe}3] [RE = Gd (3), Dy (4)] were compared and used either as single source precursors or together with ammonia for MOCVD of gadolinium nitride (GdN) and dysprosium nitride (DyN), respectively. The thermal properties of the precursors were studied and the fragmentation patterns were characterized by high-resolution electron impact−mass spectrometry (HR EI-MS). The obtained nitride films were investigated using a series of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), nuclear reaction analysis (NRA), Rutherford backscattering (RBS), and X-ray photoelectron spectroscopy (XPS). The films contain preferentially oriented grains of fcc-GdN and DyN and are contaminated with small amounts of carbon and oxygen (significantly below 10 at. % in the best cases). The temperature-dependent magnetic properties of the films, as measured using a superconducting quantum interference device (SQUID), suggest the existence of small ferromagnetic grains of the rare-earth nitrides that exhibit superparamagnetism. Despite the chemical and structural similarity of the guanidinato and amidinato complexes (1−4), a distinctly different behavior as MOCVD precursors was found for 1 and 2, compared with that for 3 and 4. While the guanidinates operate well as single-source precursors (SSPs), the amidinates are not suited at all as SSPs, but give very good nitride films when used in the presence of ammonia. This characteristic behavior was correlated with the different fragmentation mechanisms, as revealed by EI-MS.Keywords: chemical vapor deposition; magnetic materials;
Co-reporter:Daniela Bekermann;Arne Ludwig;Teodor Toader;Chiara Maccato;Davide Barreca;Alberto Gasparotto;Claudia Bock;Andreas D. Wieck;Ulrich Kunze;Eugenio Tondello;Rol A. Fischer
Chemical Vapor Deposition 2011 Volume 17( Issue 4-6) pp:155-161
Publication Date(Web):
DOI:10.1002/cvde.201006898
Abstract
Two closely related bis(ketoiminato) zinc precursors, which are air stable and possess favorable properties for metal-organic (MO)CVD, are successfully employed for the growth of ZnO films on silicon and borosilicate glass substrates at temperatures between 400 and 700 °C. The as-deposited films are investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), nuclear reaction analysis (NRA), as well as by UV-vis absorption spectroscopy and photoluminescence (PL) measurements. The structure, morphology, and composition of the as-grown films show a strong dependence on the substrate temperature. The formation of pure and (001)-oriented wurtzite-type stoichiometric ZnO is observed. PL measurements are performed both at room temperature and 77 K, revealing a defect-free emission of ZnO films.
Co-reporter:Daniela Bekermann;Detlef Rogalla;Hans-Werner Becker;Manuela Winter;Rol A. Fischer
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 9) pp:1366-1372
Publication Date(Web):
DOI:10.1002/ejic.200901037
Abstract
Two new bis(ketoiminato)zinc(II) compounds that show excellent precursor properties for the chemical vapor deposition (CVD) of zinc oxide materials are presented. The synthesis of the ketoiminato zinc complexes [Zn{[(CH2)xOCH3]NC(CH3)=C(H)C(CH3)=O}2] (1: x = 2; 2: x = 3) is straightforward and can easily be scaled up. Compounds 1 and 2 were analyzed by 1H and 13C NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction analysis, and electron ionization mass spectrometry. The compounds exist as monomers with a distorted tetrahedral zinc center. Thermogravimetric studies, sublimation, and solubility tests reveal very promising properties for metal–organic CVD related applications. Preliminary metal–organic CVD experiments with the use of compound 1 were performed as a screening for the suitability of the new bis(ketoiminato)zinc complexes as precursors for the growth of ZnO thin films in the presence of oxygen. The films were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive analysis of X-ray, and Rutherford backscattering measurements. The as-deposited ZnO films were stoichiometric; the crystalline films exhibited strong preferred orientation along the c-axis.
Co-reporter:Ke Xu;Andrian P. Milanov;Manuela Winter;Davide Barreca;Alberto Gasparotto;Hans-Werner Becker
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 11) pp:1679-01688
Publication Date(Web):
DOI:10.1002/ejic.200901225
Abstract
The synthesis and characterization of four new heteroleptic complexes [Hf{η2-(iPrN)2CNMe2}2Cl2] (1), [Hf{η2-(iPrN)2CNMe2}2Me2] (2), [Hf{η2-(iPrN)2CMe}2Cl2] (3), and [Hf{η2-(iPrN)2CMe}2Me2] (4) are reported. All the complexes were characterized by spectroscopic methods, while compounds 1–3 were further examined by single-crystal X-ray diffraction, revealing that the complexes are monomers with the hafnium center in a distorted octahedral geometry. The thermal properties of the chlorine-free complexes (2, 4) were examined to determine their suitability for metalorganic chemical vapor deposition (MOCVD) applications, and compound 2 showed good volatility and thermal stability. On the basis of these results, compound 2 was selected for MOCVD of HfO2 with oxygen as oxidant. Depositions were carried out on Si(100) substrates in the temperature range 300–700 °C. The as-deposited HfO2 films crystallized in the monoclinic phase at temperatures above 500 °C, and the composition analysis determined by Rutherford back-scattering (RBS) and X-ray photoelectron spectroscopy (XPS) revealed that the films were stoichiometric and free of carbon. Thus, alkylguanidinatohafnium complex 2 is a promising precursor for growing HfO2 films in a wide temperature range with the desired stoichiometry, because of its adequate volatility, sufficient temperature window between vaporization and decomposition, as well as its ability to decompose cleanly in the presence of oxygen.
Co-reporter:Anjana Devi;Malte Hellwig;Davide Barreca;Harish Parala;Reji Thomas;Hans-Werner Becker;Ram. S. Katiyar;Rol A. Fischer;Eugenio Tondello
Chemical Vapor Deposition 2010 Volume 16( Issue 4-6) pp:157-165
Publication Date(Web):
DOI:10.1002/cvde.200906813
Abstract
Titanium oxide (TiO2) and titanium-tantalum oxide (Ti-Ta-O) thin films are deposited by liquid injection (LI) metal-organic (MO) CVD using metal amide-malonate complexes, [Ti(NR2)2(dbml)2], and tantalum, [Ta(NMe2)4(dbml)] (R = Me, Et; dbml = di-tert-butylmalonato). TiO2 and Ti-Ta-O films are deposited on Si(100) in the temperature ranges 350–650 °C and 500–700 °C, respectively. The structure, morphology, and chemical composition of the films are evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Rutherford backscattering spectroscopy (RBS), and X-ray photoelectron spectroscopy (XPS). The electrical properties of the films, namely the dielectric properties, are assessed by carrying out capacitance-voltage (C-V) measurements on metal-oxide-semiconductor (MOS) capacitor structures.
Co-reporter:Andrian P. Milanov ; Ke Xu ; Apurba Laha ; Eberhard Bugiel ; Ramadurai Ranjith ; Dominik Schwendt ; H. Jörg Osten ; Harish Parala ; Roland A. Fischer
Journal of the American Chemical Society 2009 Volume 132(Issue 1) pp:36-37
Publication Date(Web):December 14, 2009
DOI:10.1021/ja909102j
This work documents the first example of deposition of high-quality Gd2O3 thin films in a surface-controlled, self-limiting manner by a water-based atomic layer deposition (ALD) process using the engineered homoleptic gadolinium guanidinate precursor [Gd(DPDMG)3]. The potential of this class of compound is demonstrated in terms of a true ALD process, exhibiting pronounced growth rates, a high-quality interface between the film and the substrate without the need for any additional surface treatment prior to the film deposition, and most importantly, encouraging electrical properties.
Co-reporter:Andrian P. Milanov, Teodor Toader, Harish Parala, Davide Barreca, Alberto Gasparotto, Claudia Bock, Hans-Werner Becker, Divine K. Ngwashi, Richard Cross, Shashi Paul, Ulrich Kunze, Roland A. Fischer and Anjana Devi
Chemistry of Materials 2009 Volume 21(Issue 22) pp:5443
Publication Date(Web):October 21, 2009
DOI:10.1021/cm902123m
The application of two novel metalorganic complexes, namely the isostructural tris(N,N’-diisopropyl-2-dimethlyamido-guanidinato)gadolinium(III) (1) and tris(N,N’-diisopropyl-2-dimethlyamido-guanidinato)dysprosium(III) (2) as precursors for metalorganic chemical vapor deposition (MOCVD) of Gd2O3 and Dy2O3 is discussed. On the basis of the detailed thermal gravimetric analysis (TGA) and isothermal TGA studies, both the precursors are very volatile and able to deliver continuous mass transport into the gas phase. The extraordinary thermal stability of the precursors was revealed by nulcear magnetic resonance (NMR) decomposition studies. Depositions were carried out in the presence of oxygen at reduced pressure and varying the substrate temperature in the range 300−700 °C. Uniform films with reproducible quality were deposited on Si(100) and Al2O3(0001) substrates over the entire temperature range. Employing a multitechnique approach (XRD, SEM, AFM, EDX, XPS, RBS, SNMS, C−V), variations of the growth characteristics and film properties with deposition temperature are studied in terms of crystallinity, structure, surface roughness, composition, and electrical properties.
Co-reporter:Ramasamy Pothiraja, Andrian P. Milanov, Davide Barreca, Alberto Gasparotto, Hans-Werner Becker, Manuela Winter, Roland A. Fischer and Anjana Devi
Chemical Communications 2009 (Issue 15) pp:1978-1980
Publication Date(Web):25 Feb 2009
DOI:10.1039/B821128K
Novel volatile compounds of hafnium, namely tetrakis-N,O-dialkylcarbamato hafnium(IV) [Hf(iPrNC(O)OiPr)4] (1) and tetrakis-N,N,N’-trialkylureato hafnium(IV) [Hf(iPrNC(O)N-(Me)Et)4] (2), have been synthesized through the simple insertion reaction of isopropyl isocyanate into hafnium isopropoxide and hafnium ethylmethylamide, respectively; based on the promising thermal properties, compound 1 has been evaluated as a precursor for metalorganic chemical vapor deposition (MOCVD) of HfO2 thin films, which resulted in the growth of stoichiometric and crystalline layers with a uniform morphology at temperature as low as 250 °C.
Co-reporter:Ramasamy Pothiraja, Andrian Milanov, Harish Parala, Manuela Winter, Roland A. Fischer and Anjana Devi
Dalton Transactions 2009 (Issue 4) pp:2009
Publication Date(Web):21 Nov 2008
DOI:10.1039/B810528F
New Hf and Zr malonate complexes have been synthesized by the reaction of metal amides with different malonate ligands (L = dimethyl malonate (Hdmml), diethyl malonate (Hdeml), di-tert-butyl malonate (Hdbml) and bis(trimethylsilyl) malonate (Hbsml)). Homoleptic eight-coordinated monomeric compounds of the type ML4 were obtained for Hf with all the malonate ligands employed. In contrast, for Zr only Hdmml and Hdeml yielded the eight-coordinated monomeric compounds of the type ML4, while using the bulky Hdbml and Hbsml ligands resulted into mixed alkoxo-malonato six-coordinated compounds of the type [ML2(OR)2]. Single crystal X-ray diffraction studies of all the compounds are presented and discussed, and they are found to be monomeric. The complexes are solids and in solution, they retain their monomeric nature as evidenced by NMR measurements. Compared to the classical β-diketonate complexes, [M(acac)4] and [M(thd)4] (M = Hf, Zr; acac: acetylacetonate; thd: tetramethylheptadione), the new malonate compounds are more volatile, decompose at lower temperatures and have lower melting points. In particular, the homoleptic diethyl malonate complexes of Hf and Zr melt at temperatures as low as 62 °C. In addition, the compounds are very stable in air and can be sublimed quantitatively. The promising thermal properties makes these compounds interesting for metal-organic chemical vapor deposition (MOCVD). This was demonstrated by depositing HfO2 and ZrO2 thin films successfully with two representative Hf and Zr complexes.
Co-reporter:Malte Hellwig;Ke Xu;Davide Barreca;Alberto Gasparotto;Manuela Winter;Eugenio Tondello;Rol A. Fischer
European Journal of Inorganic Chemistry 2009 Volume 2009( Issue 8) pp:1110-1117
Publication Date(Web):
DOI:10.1002/ejic.200801062
Abstract
Five different homoleptic gallium complexes with malonic diester anions [Ga(ROCOCHOCOR)3] [R = Me (1), Et (2), iPr (3), tBu (4) and SiMe3 (5)] have been synthesised and characterised by 1H and 13C NMR, IR spectroscopy, electron ionisation mass spectrometry (EI-MS), and single-crystal X-ray diffraction. The thermal properties of the obtained compounds were evaluated by thermogravimetric studies to assess their suitability as precursors for the metal-organic chemical vapour deposition (MOCVD) of Ga2O3 thin films. MOCVD of Ga2O3 thin films was carried out starting from compound 2 in light of the promising features of this precursor. The as-deposited layers are amorphous and can be transformed into the monoclinic β-Ga2O3 phase upon annealing at 1000 °C ex situ. The film morphology was studied by scanning electron microscopy (SEM), and its composition was investigated by energy-dispersive X-ray spectroscopy (EDXS) and X-ray photoelectron spectroscopy (XPS). Almost stoichiometric Ga2O3 thin films with low levels of carbon incorporation were obtained.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Co-reporter:D. Bekermann, D. Barreca, A. Gasparotto, H.W. Becker, R.A. Fischer, A. Devi
Surface and Coatings Technology 2009 204(4) pp: 404-409
Publication Date(Web):
DOI:10.1016/j.surfcoat.2009.07.029
Co-reporter:Malte Hellwig, Andrian Milanov, Davide Barreca, Jean-Laurent Deborde, Reji Thomas, Manuela Winter, Ulrich Kunze, Roland A. Fischer and Anjana Devi
Chemistry of Materials 2007 Volume 19(Issue 25) pp:6077
Publication Date(Web):November 8, 2007
DOI:10.1021/cm0630441
The stabilization of the reactive amide complexes of niobium and tantalum with malonates as chelating ligands leads to stable six-coordinated monomeric complexes ([M(NMe2)4(dbml)]; M = Nb, Ta), namely tetrakis(dimethylamido)(di-tert-butylmalonato)niobium(V) (1) and tetrakis(dimethylamido)(di-tert-butylmalonato)tantalum(V) (2). Compounds 1 and 2 were characterized by 1H NMR, 13C NMR, EI-mass spectroscopy, elemental analysis, and single-crystal X-ray diffraction studies. The thermal properties of the compounds were studied by thermogravimetric analysis. Both the complexes possess good thermal characteristics, improved resistance to air and moisture, and high solubility and stability in solvents compared to their respective parent alkyl amides. Compound 1 was studied for metalorganic chemical vapor deposition (MOCVD) of Nb2O5 while compound 2 was studied for liquid injection metalorganic chemical vapor deposition (LI-MOCVD) of Ta2O5 thin films. The films were deposited at substrate temperatures from 400 to 800 °C, and for both Nb2O5 and Ta2O5 the maximum growth rate was at 600 °C. The films were characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy for their crystallinity and morphology. Thin film composition was analyzed by X-ray photoelectron spectroscopy, Rutherford backscattering, and depth profiling the composition with secondary neutral mass spectrometry. Electrical properties of the films were studied in terms of the C–V characteristics.
Co-reporter:Anjana Devi, Raghunandan Bhakta, Andrian Milanov, Malte Hellwig, Davide Barreca, Eugene Tondello, Reji Thomas, Peter Ehrhart, Manuela Winter and Roland Fischer
Dalton Transactions 2007 (Issue 17) pp:1671-1676
Publication Date(Web):07 Feb 2007
DOI:10.1039/B616861B
A new zirconium complex, bis-(ethylmethylamido)-bis-(N,N′-diisopropyl-2-ethylmethylamidoguanidinato)-zirconium(IV) {[(NiPr)2C(NEtMe)]2Zr(NEtMe)2}, was synthesised by partial replacement of amide ligands with bidentate guanidinate ligands. The monomeric Zr complex was characterised by 1H-NMR, 13C-NMR, EI-MS, elemental analysis, and single crystal X-ray diffraction studies. The thermal properties of the compound was studied by thermogravimetric and differential thermal analysis (TG/DTA). The new Zr compound is thermally stable and can be sublimed quantitatively which renders it promising for thin film growth using vapor deposition techniques like chemical vapor deposition (CVD) and atomic layer deposition (ALD). The use of this complex for CVD of ZrO2 on Si(100) substrates was attempted in combination with oxygen as the oxidant. Stoichiometric ZrO2 films with preferred orientation at lower growth temperatures was obtained and the films were almost carbon free. The preliminary electrical characterisation of ZrO2 films showed encouraging results for possible applications in dielectric oxide structures.
Co-reporter:R. Thomas;R. Bhakta;A. Milanov;A. Devi;P. Ehrhart
Chemical Vapor Deposition 2007 Volume 13(Issue 2-3) pp:
Publication Date(Web):14 MAR 2007
DOI:10.1002/cvde.200606512
Ultrathin ZrO2 films were deposited on SiOx/Si in a multiwafer planetary metal-organic (MO)CVD reactor combined with a liquid delivery system. Two different alkoxide-based precursors, [Zr(OiPr)2(tbaoac)2] and [Zr(OtBu)2(tbaoac)2] are compared with two amide-based precursors, [Zr(NEt2)2(dbml)2] and [Zr(NEtMe)2(guanid)2]. Growth rate, surface roughness, density, and crystallization behavior are compared over a wide range of deposition temperatures (400–700 °C). In addition, the influence of the solvents, n-butylacetate, toluene, and hexane, is discussed. The best growth results in terms of low temperature deposition rate, surface roughness, film density, and carbon content were obtained for the new [Zr(NEtMe)2(guanid)2] precursor. The electrical properties were investigated with metal–insulator–semiconductor (MIS) capacitors. The relative dielectric permittivity was in the range 17–24, depending on the precursor. Compared to standard SiO2 capacitors of similar equivalent oxide thickness, low leakage currents were obtained.
Co-reporter:A. Milanov, R. Bhakta, R. Thomas, P. Ehrhart, M. Winter, R. Waser and A. Devi
Journal of Materials Chemistry A 2006 vol. 16(Issue 5) pp:437-440
Publication Date(Web):15 Dec 2005
DOI:10.1039/B509380E
The concept of introducing malonates as chelating ligands in combination with metal amides has yielded a new class of compounds which enable growth of HfO2 thin films at low deposition temperatures by liquid injection metalorganic chemical vapour deposition.
Co-reporter:R. Thomas;A. Milanov;R. Bhakta;U. Patil;M. Winter;P. Ehrhart;R. Waser;A. Devi
Chemical Vapor Deposition 2006 Volume 12(Issue 5) pp:
Publication Date(Web):19 MAY 2006
DOI:10.1002/cvde.200506481
The stabilization of highly reactive amide complexes of zirconium diethylamide with malonates as chelating ligands leads to a stable six-coordinated monomeric complex which shows promise for CVD applications. This novel precursor, zirconium bis-(diethylamido)bis(di-tert-butylmalonato) zirconium, [Zr(NEt2)2(dbml)2], has been characterized and tested in a production-type MOCVD reactor for ZrO2 thin-film deposition. Up to 450 °C, the ZrO2 films are amorphous, and above 475 °C films they are crystalline. Atomic force microscopy (AFM) shows a lower roughness (∼2.5Å) for as-deposited amorphous films compared to crystalline films (∼6.0 Å); however, smooth crystalline films can be obtained by post-deposition annealing of amorphous films. Electrical properties are investigated for Pt/ZrO2/SiOx/Si capacitor structures. Relative dielectric permittivity reaches a bulk value of 24, and leakage currents for typically 4 nm thick films are below 10–4 A cm–2 at a bias of –1 V. Hence, the precursor shows promising properties for possible application in the deposition of high-k gate oxide (MIS) and high-k dielectric (MIM) structures.
Co-reporter:U. Patil;R. Thomas;A. Milanov;R. Bhakta;P. Ehrhart;R. Waser;R. Becker;H.-W. Becker;M. Winter;K. Merz;R. A. Fischer;A. Devi
Chemical Vapor Deposition 2006 Volume 12(Issue 2-3) pp:
Publication Date(Web):22 MAR 2006
DOI:10.1002/cvde.200506394
Metal-organic precursors of Zr and Hf with excellent vaporization characteristics and low decomposition temperatures are reported. The new mixed alkoxide precursors [Zr(OtBu)2(tbaoac)2] (1) and [Hf(OtBu)2(tbaoac)2] (2) were synthesized by facile alcohol-exchange reactions between [M(OiPr)2(L)2] and tert-butanol [M = Zr, Hf; L = tert-butylacetoacetate (tbaoac)]. The six-coordinated monomeric compounds are volatile, stable in solution, and less sensitive to air and moisture compared to parent alkoxides such as [Zr(OtBu)4] and [Hf(OtBu)4]. It was possible to grow ZrO2 and HfO2 at low deposition temperatures, and the films were characterized by X-ray diffraction ( XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Rutherford back scattering (RBS) analysis. [Zr(OtBu)2(tbaoac)2], evaluated in a multiwafer planetary MOCVD reactor combined with a liquid delivery system, yielded ZrO2 films that show promise for gate oxide applications.
Co-reporter:Andrian P. Milanov ; Roland A. Fischer
Inorganic Chemistry () pp:
Publication Date(Web):November 6, 2008
DOI:10.1021/ic801432b
Eight novel homoleptic tris-guanidinato complexes M[(NiPr)2CNR2]3 [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), iPr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The iPr-Me2N-guanidinates of Y, Gd and Dy (1a−c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the iPr-Me2N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that iPr-Me2N-guanidinates of Y, Gd and Dy (1a−c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd2O3 and Dy2O3 thin films on Si(100) substrates. The MOCVD grown films of Gd2O3 and Dy2O3 were highly oriented in the cubic phase, while the ALD grown films were amorphous.
Co-reporter:Sarah Karle, Detlef Rogalla, Arne Ludwig, Hans-Werner Becker, Andreas Dirk Wieck, Markus Grafen, Andreas Ostendorf and Anjana Devi
Dalton Transactions 2017 - vol. 46(Issue 8) pp:NaN2679-2679
Publication Date(Web):2017/02/07
DOI:10.1039/C6DT04399B
Novel copper ketoiminate compounds were synthesized and for the first time applied for additive-free solution-based deposition of nanoscale copper oxide thin films. The two closely related compounds, namely the bis[4-(2-ethoxyethyl-imino)-3-pentanonato]copper, [Cu(EEKI)2], and bis[4-(3-methoxypropylimino)-3-pentanonato]copper, [Cu(MPKI)2], were characterized by means of elemental and thermogravimetric analysis (TGA), as well as electron impact mass spectrometry (EI-MS). The advantages of these compounds are that they are liquid and possess excellent solubility in common organic solvents in addition to an optimum reactivity towards ambient moisture that enables a facile solution-based approach to nanoscale copper oxide thin films. Moreover, no additives or aging is needed to stabilize the solution processing of the copper oxide layers. [Cu(MPKI)2] was tested in detail for the deposition of copper oxide thin films by spin coating. Upon one-step annealing, high-quality, uniform, crystalline copper oxide thin films were deposited on Si, SiO2, as well as on quartz substrates. Structural, morphological and compositional characteristics of the copper oxide nanostructures were investigated in detail by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and a combined analysis using Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA). It was possible to control the copper oxide phases (CuO and Cu2O) by systematic tuning of the post-deposition annealing conditions. The functional properties in terms of optical band gap were investigated using UV/Vis spectroscopy, while the transport properties, such as resistivity, mobility and carrier concentration were analyzed employing Hall measurements, which confirmed the p-type conductivity of the copper oxide layers.
Co-reporter:Ramasamy Pothiraja, Andrian P. Milanov, Davide Barreca, Alberto Gasparotto, Hans-Werner Becker, Manuela Winter, Roland A. Fischer and Anjana Devi
Chemical Communications 2009(Issue 15) pp:NaN1980-1980
Publication Date(Web):2009/02/25
DOI:10.1039/B821128K
Novel volatile compounds of hafnium, namely tetrakis-N,O-dialkylcarbamato hafnium(IV) [Hf(iPrNC(O)OiPr)4] (1) and tetrakis-N,N,N’-trialkylureato hafnium(IV) [Hf(iPrNC(O)N-(Me)Et)4] (2), have been synthesized through the simple insertion reaction of isopropyl isocyanate into hafnium isopropoxide and hafnium ethylmethylamide, respectively; based on the promising thermal properties, compound 1 has been evaluated as a precursor for metalorganic chemical vapor deposition (MOCVD) of HfO2 thin films, which resulted in the growth of stoichiometric and crystalline layers with a uniform morphology at temperature as low as 250 °C.
Co-reporter:Ke Xu, Ayan Roy Chaudhuri, Harish Parala, Dominik Schwendt, Teresa de los Arcos, H. Jörg Osten and Anjana Devi
Journal of Materials Chemistry A 2013 - vol. 1(Issue 25) pp:NaN3946-3946
Publication Date(Web):2013/04/17
DOI:10.1039/C3TC30401A
For the first time, the combination of the homoleptic erbium tris-guanidinate metalorganic complex ([Er(NMe2-Guan)3]) simply with water yielded high quality Er2O3 thin films on Si(100) substrates employing the atomic layer deposition (ALD) process. The process optimization to grow good quality Er2O3 layers was performed by varying the Er precursor pulse time, water pulse time and purge time. The high reactivity of the Er compound towards water and good thermal stability in the temperature range of 150–275 °C (ALD window) resulted in homogeneous, stoichiometric Er2O3 layers with high growth rates (1.1 Å per cycle) and the as-deposited films crystallized in the cubic phase. The saturation behavior at different temperatures in the ALD window and the linear dependence of film thickness as a function of precursor pulse time confirmed the true ALD process. The potential of Er2O3 thin films as gate dielectrics was verified by performing capacitance–voltage (C–V) and current–voltage (I–V) measurements. Dielectric constants estimated from the accumulation capacitance were found to be in the range of 10–13 for layers of different thicknesses (15–30 nm).
Co-reporter:M. Gebhard, M. Hellwig, H. Parala, K. Xu, M. Winter and A. Devi
Dalton Transactions 2014 - vol. 43(Issue 3) pp:NaN940-940
Publication Date(Web):2013/11/22
DOI:10.1039/C3DT52746H
Two closely related mononuclear homoleptic indium-tris-guanidinate complexes have been synthesized and characterized as precursors for atomic layer deposition (ALD) of In2O3. In a water assisted ALD process, high quality In2O3 thin films have been fabricated for the first time using the new class of precursors as revealed by the promising ALD growth characteristics and film properties.
Co-reporter:Richard O’ Donoghue, Daniel Peeters, Detlef Rogalla, Hans-Werner Becker, Julian Rechmann, Sebastian Henke, Manuela Winter and Anjana Devi
Dalton Transactions 2016 - vol. 45(Issue 47) pp:NaN19023-19023
Publication Date(Web):2016/10/25
DOI:10.1039/C6DT03571J
Molecular engineering of seven closely related zinc ketoiminates, namely, [Zn(dapki)2], [Zn(daeki)2], [Zn(epki)2], [Zn(eeki)2], [Zn(mpki)2], [Zn(meki)2], and [Zn(npki)2], leads to the optimisation of precursor thermal properties in terms of volatilisation rate, onset of volatilisation, reactivity and thermal stability. The influence of functional groups at the imine side chain of the ligands on the precursor properties is studied with regard to their viability as precursors for atomic layer deposition (ALD) of ZnO. The synthesis of [Zn(eeki)2], [Zn(epki)2] and [Zn(dapki)2] and the crystal structures of [Zn(mpki)2], [Zn(eeki)2], [Zn(dapki)2] and [Zn(npki)2] are presented. From the investigation of the physico-chemical characteristics, it was inferred that all compounds are monomeric, volatile and exhibit high thermal stability, all of which make them promising ALD precursors. Compound [Zn(eeki)2] is in terms of thermal properties the most promising Zn-ketoiminate. It is reactive towards water, possesses a melting point of 39 °C, is stable up to 24 days at 220 °C and has an extended volatilisation rate compared to the literature known Zn-ketoiminates. It demonstrated self-saturated, water assisted growth of zinc oxide (ZnO) with growth rates in the order of 1.3 Å per cycle. Moreover, it displayed a broad temperature window from TDep = 175–300 °C and is the first report of a stable high temperature (>200 °C) ALD process for ZnO returning highly promising growth rates.
Co-reporter:M. Gebhard, F. Mitschker, M. Wiesing, I. Giner, B. Torun, T. de los Arcos, P. Awakowicz, G. Grundmeier and A. Devi
Journal of Materials Chemistry A 2016 - vol. 4(Issue 5) pp:NaN1065-1065
Publication Date(Web):2016/01/11
DOI:10.1039/C5TC03385C
An efficient plasma-enhanced atomic layer deposition (PE-ALD) process was developed for TiO2 thin films of high quality, using a new Ti-precursor, namely tris(dimethylamido)-(dimethylamino-2-propanolato)titanium(IV) (TDMADT). The five-coordinated titanium complex is volatile, thermally stable and reactive, making it a potential precursor for ALD and PE-ALD processes. Process optimization was performed with respect to plasma pulse length and reactive gas flow rate. Besides an ALD window, the application of the new compound was investigated using in situ quartz-crystal microbalance (QCM) to monitor surface saturation and growth per cycle (GPC). The new PE-ALD process is demonstrated to be an efficient procedure to deposit stoichiometric titanium dioxide thin films under optimized process conditions with deposition temperatures as low as 60 °C. Thin films deposited on Si(100) and polyethylene-terephthalate (PET) exhibit a low RMS roughness of about 0.22 nm. In addition, proof-of-principle studies on TiO2 thin films deposited on PET show promising results in terms of barrier performance with oxygen transmission rates (OTR) found to be as low as 0.12 cm3 × cm−2 × day−1 for 14 nm thin films.
Co-reporter:Anjana Devi, Raghunandan Bhakta, Andrian Milanov, Malte Hellwig, Davide Barreca, Eugene Tondello, Reji Thomas, Peter Ehrhart, Manuela Winter and Roland Fischer
Dalton Transactions 2007(Issue 17) pp:NaN1676-1676
Publication Date(Web):2007/02/07
DOI:10.1039/B616861B
A new zirconium complex, bis-(ethylmethylamido)-bis-(N,N′-diisopropyl-2-ethylmethylamidoguanidinato)-zirconium(IV) {[(NiPr)2C(NEtMe)]2Zr(NEtMe)2}, was synthesised by partial replacement of amide ligands with bidentate guanidinate ligands. The monomeric Zr complex was characterised by 1H-NMR, 13C-NMR, EI-MS, elemental analysis, and single crystal X-ray diffraction studies. The thermal properties of the compound was studied by thermogravimetric and differential thermal analysis (TG/DTA). The new Zr compound is thermally stable and can be sublimed quantitatively which renders it promising for thin film growth using vapor deposition techniques like chemical vapor deposition (CVD) and atomic layer deposition (ALD). The use of this complex for CVD of ZrO2 on Si(100) substrates was attempted in combination with oxygen as the oxidant. Stoichiometric ZrO2 films with preferred orientation at lower growth temperatures was obtained and the films were almost carbon free. The preliminary electrical characterisation of ZrO2 films showed encouraging results for possible applications in dielectric oxide structures.
Co-reporter:Ramasamy Pothiraja, Andrian Milanov, Harish Parala, Manuela Winter, Roland A. Fischer and Anjana Devi
Dalton Transactions 2009(Issue 4) pp:-663
Publication Date(Web):2008/11/21
DOI:10.1039/B810528F
New Hf and Zr malonate complexes have been synthesized by the reaction of metal amides with different malonate ligands (L = dimethyl malonate (Hdmml), diethyl malonate (Hdeml), di-tert-butyl malonate (Hdbml) and bis(trimethylsilyl) malonate (Hbsml)). Homoleptic eight-coordinated monomeric compounds of the type ML4 were obtained for Hf with all the malonate ligands employed. In contrast, for Zr only Hdmml and Hdeml yielded the eight-coordinated monomeric compounds of the type ML4, while using the bulky Hdbml and Hbsml ligands resulted into mixed alkoxo-malonato six-coordinated compounds of the type [ML2(OR)2]. Single crystal X-ray diffraction studies of all the compounds are presented and discussed, and they are found to be monomeric. The complexes are solids and in solution, they retain their monomeric nature as evidenced by NMR measurements. Compared to the classical β-diketonate complexes, [M(acac)4] and [M(thd)4] (M = Hf, Zr; acac: acetylacetonate; thd: tetramethylheptadione), the new malonate compounds are more volatile, decompose at lower temperatures and have lower melting points. In particular, the homoleptic diethyl malonate complexes of Hf and Zr melt at temperatures as low as 62 °C. In addition, the compounds are very stable in air and can be sublimed quantitatively. The promising thermal properties makes these compounds interesting for metal-organic chemical vapor deposition (MOCVD). This was demonstrated by depositing HfO2 and ZrO2 thin films successfully with two representative Hf and Zr complexes.
Co-reporter:Andrian P. Milanov, Ke Xu, Stefan Cwik, Harish Parala, Teresa de los Arcos, Hans-Werner Becker, Detlef Rogalla, Richard Cross, Shashi Paul and Anjana Devi
Dalton Transactions 2012 - vol. 41(Issue 45) pp:NaN13947-13947
Publication Date(Web):2012/09/04
DOI:10.1039/C2DT31219K
Alternative novel precursor chemistries for the vapor phase deposition of rare-earth (RE) oxide thin films were developed by synthesising the homoleptic guanidinate compounds tris(N,N′-diisopropyl-2-dimethylamidoguanidinato)-scandium(III) [Sc(DPDMG)3] (1), tris(N,N′-diisopropyl-2-dimethylamidoguanidinato)-erbium(III), [Er(DPDMG)3] (2) and tris(N,N′-diisopropyl-2-dimethylamidoguanidinato)-yttrium(III), [Y(DPDMG)3] (3). All three compounds are monomeric as revealed by single crystal X-ray diffraction (XRD) analysis, nuclear magnetic resonance (NMR) and electron impact mass spectrometry (EI-MS). The thermal analysis revealed that the compounds are volatile and very stable under evaporation conditions. Therefore the complexes were evaluated as precursors for the growth of Sc2O3, Er2O3 and Y2O3 thin films, respectively, by metal–organic chemical vapor deposition (MOCVD). Uniform Sc2O3, Er2O3 and Y2O3 films on Si(100) substrates with reproducible quality were grown by MOCVD by the combination of the respective guanidinate precursors and oxygen in the temperature range 350–700 °C. The structural, morphological, compositional and electrical properties of the films were investigated in detail. The most relevant film properties are highlighted in relation to the distinct advantages of the novel precursor chemistries in comparison to the commonly used literature known RE precursors. This study shows that compounds 1–3 are very good precursors for MOCVD yielding Sc2O3, Er2O3 and Y2O3 thin films which are stoichiometric and display suitable electrical properties for their potential use as high dielectric constant (high-k) materials.
Co-reporter:Manish Banerjee, Rüdiger W. Seidel, Manuela Winter, Hans-Werner Becker, Detlef Rogalla and Anjana Devi
Dalton Transactions 2014 - vol. 43(Issue 6) pp:NaN2396-2396
Publication Date(Web):2013/11/08
DOI:10.1039/C3DT52335G
Treatment of tetrakis(diethylamido)zirconium(IV); [Zr(NEt2)4] with a series of β-ketoimines ({[RHN]C(CH3)C(H)C(CH3)O} where R is a functionalized side-chain; 4-(2-methoxyethylamino)pent-3-en-2-one, Hmeap; 4-(3-methoxypropylamino)pent-3-en-2-one, Hmpap; 4-(2-(dimethylamino)ethylamino)pent-3-en-2-one, Hdeap; 4-(3-(dimethylamino)propylamino)pent-3-en-2-one, Hdpap) leads to an amine substitution reaction that yielded novel monomeric heteroleptic mixed amido-ketoiminato complexes of the type bis(4-(2-methoxyethylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (1), bis(4-(3-methoxypropylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (2), and bis(4-(3-(dimethylamino)propylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (3), and eight-coordinated homoleptic complexes tetrakis(4-(2-methoxyethylamino)pent-3-en-2-onato)zirconium(IV) (4) and tetrakis(4-(2-(dimethylamino)ethylamino)pent-3-en-2-onato)zirconium(IV) (5), depending on the ratio of the ligand to zirconium. Adopting a similar strategy with zirconium alkoxide, namely [Zr(OiPr)4·iPrOH], with β-ketoimine Hmeap, leads to the formation of a dimer, bis(μ2-isopropoxo)bis(4-(2-methoxyethylamino)pent-3-en-2-onato)tetrakis(isopropoxo)dizirconium(IV) (6). The newly synthesised complexes were characterized by NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, elemental analysis and thermal analysis. The low decomposition temperature facilitated by the stepwise elimination of the ketominate ligand from the complex and the stability of the complexes obtained in air as well as in solution makes them highly suitable for solution based processing of ZrO2 thin films, which is demonstrated using compound 5 on Si(100) substrates. High quality ZrO2 films were obtained and were investigated for their structure, morphology, composition and optical properties. Low temperature crystallisation of ZrO2 is achieved by a simple chemical deposition process using the new class of Zr precursors and the films exhibit an optical transmittance above 90%.
