Co-reporter:Fen Qiao;Xuewan Wang;Qian Wang;Yi Xie
Nanoscale (2009-Present) 2017 vol. 9(Issue 24) pp:8066-8079
Publication Date(Web):2017/06/22
DOI:10.1039/C7NR01974B
In comparison to randomly oriented nanorods (NRs), self-assembly of the colloidal CdX (X = S, Se) NRs into well-organized large-scale structures results in unique collective properties. Moreover, the anisotropic structural features of self-assemblies preserved from colloidal CdX (X = S, Se) NRs have opened up exciting opportunities in the field of nanotechnology applications. We present the latest strategies for the self-assembly of colloidal NRs on solid substrates, and further focus on the self-assembled NRs for applications in devices. Advanced progress in the preparation of NR building blocks on the basis of nanofabrication techniques and comprehensive studies on the interactions of NRs with substrates will remarkably expand the application of colloidal semiconductor NRs. Understanding and mastering the driving forces behind the assembly of the NRs is the key goal of engineering future functional structures based on NRs.
Co-reporter:L. Zhu;G. He;Z. Q. Sun;M. Liu;S. S. Jiang
Journal of Sol-Gel Science and Technology 2017 Volume 83( Issue 3) pp:675-682
Publication Date(Web):17 July 2017
DOI:10.1007/s10971-017-4468-y
In current work, the microstructure and optical and electrical properties of sol–gel-derived Gd-doped ZrO2 gate dielectric thin films as functions of annealing temperatures were systemically investigated. Analyzes by x-ray diffraction have indicated that the 240 °C-baked sample as well as those samples annealed at lower temperatures keep amorphous state. In the sample annealed at 500 °C, however, the amorphous phase disappears and tetragonal ZrO2 is formed. Measurements from ultraviolet-visible spectroscopy (UV/Vis) have demonstrated that transmittance of all samples in the visible region is approximately 80% and the increase in band gap energy has been found with increasing the annealing temperature. Electrical properties of all samples based on Al/Si/ZrGdOx/Al MOS capacitor have been investigated by using semiconductor device analyzer. Through the analysis and calculation of the electrical characteristic curves, solution-processed Al/ZrGdOx/Si/Al capacitor shows improved performances at a annealing temperature of 400 °C, such as high dielectric constant (k) of 16.56, lowest oxidation charge density (Qox) of −0.74 × 1012 cm−2, and boundary trap oxidation charge density (Nbt) of 3.17 × 1012 cm−2. In addition, the leakage current mechanism for 400 °C-annealed sample has been discussed in detail.solution-processed Gd-doped ZrO2 gate dielectric films were realized. Al/ZrGdOx/Si/Al capacitor shows optimized and improved performances at a annealing temperature of 400 °C.Open image in new window
Co-reporter:J. Gao, G. He, D.Q. Xiao, S.S. Jiang, J.G. Lv, C. Cheng, Z.Q. Sun
Materials Research Bulletin 2017 Volume 91(Volume 91) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.materresbull.2017.03.042
•Sputtering-derived HfTiON gate dielectrics have been deposited on Ge substrates.•Nitrogen incorporation suppress the formation of GeO2 and germanate at the interface.•N should be carefully controlled to meet the best performance requirement for Ge-based CMOS device.Effects of nitrogen incorporation on the interface chemical bonding states, band alignment and electrical properties of sputtering-derived HfTiO high-k gate stacks on Ge substrates pretreated by trimethylaluminum (TMA) precursor have been investigated by X-ray photoemission spectroscopy (XPS), UV–vis transmission spectroscopy, and electrical measurements. XPS results indicate that incorporation of a moderate amount of nitrogen (3 sccm) incorporation can effectively suppress the formation of unstable GeO2 and low-k germinate at the interfacial region. Meanwhile, reduction in band gap and valence band offset and increase in conduction band offset have been observed after nitrogen incorporation. Electrical properties were evaluated by capacitance-voltage (C–V) and leakage current density-voltage (J–V) measurements based on MOS capacitors. Small gate leakage current (4.13 × 10−7 A/cm2 at Vg = 1 V), almost disappeared hysteresis, and large dielectric constant (19.6) that have been observed for MOS capacitor with HfTiON/Ge stacked gate dielectric with N2 flow of 3 sccm.Download high-res image (179KB)Download full-size image
Co-reporter:Jianguo Lv;Wenhao Wang;Min Zhao;Weili Zhu
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 5) pp:4051-4057
Publication Date(Web):2017 March
DOI:10.1007/s10854-016-6019-7
ZnO thin films were synthesized by a facile electrodeposition method in the aqueous solution. Porous ZnO thin films with wurtzite structure could be achieved by mean of annealing treatment. The growth mechanism of the porous ZnO thin film was discussed. The intensity of the E2 mode in the ZnO thin film, which represents crystalline quality of the thin film increases with the increasing of annealing temperature. Optical properties indicate that annealing temperature has strong effect on the optical band gap value and defect concentrations. Both the green and yellow emissions corresponding to respective oxygen vacancies and oxygen interstitials can be identified. The results show that ZnO annealed at 400 °C exhibits a significant photocurrent density enhancement which is about 18 times larger than that of the as-deposited ZnO thin films. The mechanism of the enhanced photoresponse for the ZnO thin film has been discussed in detail.
Co-reporter:Jianguo Lv;Wenhao Wang;Min Zhao
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 1) pp:1022-1027
Publication Date(Web):25 August 2016
DOI:10.1007/s10854-016-5623-x
Na2xZn1−xO thin films were successfully synthesized on quartz glass substrates by sol–gel method. The effect of Na content on the microstructure, optical properties and UV photoresponse of the thin films was investigated using X-ray diffraction, optical absorbance, photoluminescence, and conductivity measurements. The results indicate that the Na0.04Zn0.98O thin film exhibits the strongest preferential c-axis orientation with a polycrystalline hexagonal wurtzite structure and has the largest optical band gap. An obvious decrease in crystal size has been observed with the increasing of Na content. A weak ultraviolet emission band at about 381 nm and a strong visible emission band have been observed in the photoluminescence spectra. The Na0.04Zn0.98O thin film has the shortest growth and decay time (45 and 18 s, respectively) and the largest photoresponse. The results indicate that the photoresponse can be effectively improved by means of moderate Na doping.
Co-reporter:Dongqi Xiao, Gang He, Zhaoqi Sun, Jianguo Lv, Peng Jin, Changyong Zheng, Mao Liu
Ceramics International 2016 Volume 42(Issue 1) pp:759-766
Publication Date(Web):January 2016
DOI:10.1016/j.ceramint.2015.08.177
Solution-processed high-k gate dielectrics for metal-oxide-semiconductor (MOS) capacitor have been widely investigated with the objective of achieving high performance field effect transistors (FETs) for next-generation microelectronic device. In current work, the effect of postdeposition annealing temperature on the microstructure, optical and electrical properties of peroxo-zirconium oxide (ZrO2) gate dielectrics fabricated by a simple spin-coating method has been studied systemically. By means of characterization of spectroscopy ellipsometry and ultraviolet–visible spectroscopy, the thicknesses and optical constants of ZrO2 gate dielectrics have been determined precisely. The annealing temperature dependent electrical properties of ZrO2 films were determined by capacitance–voltage (C–V) and leakage current density–voltage (J–V) measurements. Based on the implementation as gate insulator, the solution-processed ZrO2-based MOS capacitor showed good and stable performances during annealing at 700 °C. As a result, the dominant leakage conduction mechanism for optimized 700 °C-annealed sample has been discussed in detail. Our results show the possibility of the solution-processed ZrO2 dielectric layer as a gate insulator for application in MOSFETs.
Co-reporter:Peng Jin, Gang He, Dongqi Xiao, Juan Gao, Mao Liu, Jianguo Lv, Yanmei Liu, Miao Zhang, Peihong Wang, Zhaoqi Sun
Ceramics International 2016 Volume 42(Issue 6) pp:6761-6769
Publication Date(Web):1 May 2016
DOI:10.1016/j.ceramint.2016.01.050
Abstract
Deposition of high-k HfO2 gate dielectric films on n-type Si and quartz substrates by sol–gel spin-on coating technique has been performed and the structural, optical and electrical characteristics as a function of annealing temperature have been investigated. The structural and optical properties of HfO2 thin films related to annealing temperature are investigated by X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), and spectroscopic ellipsometry (SE). Results indicate that the monoclinic form of HfO2 appears when temperature rises through and above 500 °C. The reduction in band gap is observed with the increase of annealing temperature. Moreover, the increase of refractive index (n) and density and the decrease of the extinction coefficient with the increase of annealing temperature are obtained by SE measurements. Additionally, the electrical properties based on Al/Si/HfO2/Al capacitor are analyzed by means of the high frequency capacitance–voltage (C–V) and the leakage current density–voltage (J–V) characteristics. And the leakage current conduction mechanisms as functions of annealing temperatures are also discussed.
Co-reporter:S.S. Jiang, G. He, J. Gao, D.Q. Xiao, P. Jin, W.D. Li, J.G. Lv, M. Liu, Y.M. Liu, Z.Q. Sun
Ceramics International 2016 Volume 42(Issue 10) pp:11640-11649
Publication Date(Web):1 August 2016
DOI:10.1016/j.ceramint.2016.04.067
Abstract
The microstructure, optical and electrical properties of HfTiO high-k gate dielectric thin films deposited on Si substrate and quartz substrate by RF magnetron sputtering have been investigated. Based on analysis from x-ray diffraction (XRD) measurements, it has been found that the as-deposited HfTiO films remain amorphous regardless of the working gas pressure. Meanwhile, combined with characterization of ultraviolet-visible spectroscopy (UV–vis) and spectroscopy ellipsometry (SE), the deposition rate, band gap and optical properties of sputtered HfTiO gate dielectrics were determined. Besides, by means of the characteristic curves of high frequency capacitance–voltage (C–V) and leakage current density–voltage (J–V), the electrical parameters, such as permittivity, total positive charge density, border trap charge density, and leakage current density, have been obtained. The leakage current mechanisms are also discussed. The energy band gap of 3.70 eV, leakage current density of 1.39×10−5 A/cm2 at bias voltage of 2 V, and total positive charge density and border trap charge density of 9.16×1011 cm−2 and 1.3×1011 cm−2, respectively render HfTiO thin films deposited at 0.6 Pa, potential high-k gate dielectrics in future CMOS devices.
Co-reporter:C.Y. Zheng, G. He, X.F. Chen, M. Liu, J.G. Lv, J. Gao, J.W. Zhang, D.Q. Xiao, P. Jin, S.S. Jiang, W.D. Li, Z.Q. Sun
Journal of Alloys and Compounds 2016 Volume 679() pp:115-121
Publication Date(Web):15 September 2016
DOI:10.1016/j.jallcom.2016.04.025
•Nitrogen content dependent sputtering-derived HfO2/IGZO heterojunction has been obtained.•Nitrogen incorporation lower band gaps and higher conduction offset.•Nitrogen incorporation suppresses the growth of low-k interfacial layer.•Improved electrical properties have been achieved after nitrogen incorporation.High-k HfOxNy and HfO2 have been applied to amorphous InGaZnO (a-IGZO) metal–oxide–semiconductor (MOS) capacitors as high-k gate dielectrics by using radio-frequency sputtering at room temperature. Effects of nitrogen incorporation on the optical band gap, band alignment and electrical properties of HfOxNy/IGZO/Si gate stacks have been systematically investigated by spectroscopic ellipsometry (SE), UV–vis spectroscopy, x-ray photoemission spectroscopy (XPS) and electrical measurements. Experimental results have confirmed the successful incorporation of nitrogen into HfO2 films and reduction in band gap with the incorporation of nitrogen for HfOxNy thin films. Reduction in valence band offset and increase in conduction band offset have been observed for HfOxNy/IGZO gate stack. Electrical properties measurements for a-IGZO MOS capacitors based on HfOxNy gate dielectrics have indicated that nitrogen incorporation leads to the improved interface quality, increased dielectric constant, reduced hysteresis voltage, and decreased leakage current density. Meanwhile, the leakage current mechanism under gate injection for MOS capacitors based on HfO2 and HfOxNy high-k gate dielectrics has been investigated systematically.
Co-reporter:Juan Gao, Gang He, Zhaoqi Sun, Hanshuang Chen, Changyong Zheng, Peng Jin, Dongqi Xiao, Mao Liu
Journal of Alloys and Compounds 2016 Volume 667() pp:352-358
Publication Date(Web):15 May 2016
DOI:10.1016/j.jallcom.2016.01.171
•ALD-derived HfAlO gate dielectric has been deposited on Si substrate.•Al2O3 incorporation into HfO2 leads to reduced leakage current.•Poole-Frenkle emission is main conduction mechanism at low field.•Direct tunneling dominates the conduction mechanism at high field.Effect of Al2O3 incorporation on the electrical properties and carrier transportation of atomic-layer-deposited (ALD) HfAlO high-k gate dielectrics on Si substrates have been investigated. Electrical analyses indicate that interfacial properties of HfAlO/Si gate stack have been improved and leakage current is reduced after Al2O3 incorporation into HfO2. Additionally, the HfAlO sample with precursor ratio (TEMAH: TMA) of 4:2 exhibits the lowest interface state density (Dit) of 3.6 × 1011 cm−2 eV−1, the lowest border trapped oxide charge density (Nbt) of 2.4 × 1011 cm−2, the lower density of oxide charge (Qox) of 0.9 × 1012 cm−2, and the lowest frequency dispersion of 0.15%. In addition, the carrier transportation mechanism for both HfO2 and HfAlO has been investigated systematically. Based on the analysis, it can be concluded that Poole-Frenkle (P–F) emission is main conduction mechanism at the low electric field, and direct tunneling (D-T) dominates the conduction mechanism at the high field, respectively.
Co-reporter:Jianguo Lv, Yue Sun, Min Zhao, Li Cao, Jiayuan Xu, Gang He, Miao Zhang, Zhaoqi Sun
Applied Surface Science 2016 Volume 366() pp:348-352
Publication Date(Web):15 March 2016
DOI:10.1016/j.apsusc.2016.01.104
Highlights
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Rectifying ZnO/FTO heterojunction was successfully synthetized.
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The sample deposited at −0.8 V has the best rectifying characteristics.
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P-type conductivity of ZnO may be attributed to hydrogen–oxygen complex defect.
Co-reporter:J.W. Zhang, G. He, M. Liu, H.S. Chen, Y.M. Liu, Z.Q. Sun, X.S. Chen
Applied Surface Science 2015 Volume 346() pp:489-496
Publication Date(Web):15 August 2015
DOI:10.1016/j.apsusc.2015.03.171
Highlights
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Sputtered Hf1−xTixO2 gate dielectrics with different TiO2 concentration have been deposited on Si substrates.
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Decrease in interfacial layer thickness reduction in band gap with increasing the TiO2 component has been determined.
- •
Hf1−xTixO2 with incorporating TiO2 of 9% shows to be a promising candidate for high-k gate dielectrics.
Co-reporter:Jianguo Lv, Jinhua Xu, Min Zhao, Pengpeng Yan, Sicong Mao, Fengjiao Shang, Gang He, Miao Zhang, Zhaoqi Sun
Ceramics International 2015 Volume 41(Issue 10) pp:13983-13987
Publication Date(Web):December 2015
DOI:10.1016/j.ceramint.2015.07.010
ZnO/Cu2O composite thin films were deposited on Cu foil using a simple solution method with a variety of ZnO seed layers inserted between the Cu2O and ZnO layers. Effects of the ZnO seed layers on the microstructure, optical properties and photoresponse of the thin films were investigated. The intensity of the ZnO (002) diffraction peak increases with increasing thickness of the seed layer. Dissolution of ZnO nanoparticles also occurs during growth of the ZnO thin films. The optical band gap of the Cu2O layer decreases gradually from 1.86 to 1.66 eV as the thickness of the ZnO seed layer increases. Change of the optical band gap could be attributed to Cu2+ impurities in the Cu2O and (or) ZnO layers. A visible emission from sample with a seed layer of four times can be attributed to phonon-assisted exciton recombination in Cu2O. An ultraviolet emission centered at 380 nm and a broad visible emission band is observed in the two samples with a seed layer of six and eight times. The best photoresponse performance has been observed in the sample with a seed layer of eight times. This is likely a result of the stronger visible absorption and better band alignment in samples, which facilitates electron transfer from the conduction band of Cu2O to the conduction band of ZnO.
Co-reporter:J.W. Zhang, G. He, T.S. Li, M. Liu, X.S. Chen, Y.M. Liu, Z.Q. Sun
Materials Research Bulletin 2015 65() pp: 7-13
Publication Date(Web):
DOI:10.1016/j.materresbull.2015.01.004
Co-reporter:Gang He, Jiangwei Liu, Hanshuang Chen, Yanmei Liu, Zhaoqi Sun, Xiaoshuang Chen, Mao Liu and Lide Zhang
Journal of Materials Chemistry A 2014 vol. 2(Issue 27) pp:5299-5308
Publication Date(Web):17 Apr 2014
DOI:10.1039/C4TC00572D
Effects of nitrogen incorporation on the interface chemical bonding states, optical dielectric function, band alignment, and electrical properties of sputtering-derived HfTiO high-k gate dielectrics on GaAs substrates have been studied by angle resolved X-ray photoemission spectroscopy (ARXPS), spectroscopy ellipsometry (SE), and electrical measurements. XPS analysis has confirmed that the interfacial layer of a HfTiO/GaAs gate stack is suppressed effectively after nitrogen incorporation. Analysis by SE has confirmed that reduction in band gap and increase in refractive index are observed with the incorporation of nitrogen. Reduction in valence band offset and increase in conduction band offset have been observed for a HfTiON/GaAs gate stack. Electrical measurements based on metal-oxide-semiconductor (MOS) capacitors have shown that the MOS capacitor with a HfTiON/GaAs stacked gate dielectric annealed at 600 °C exhibits low interface-state density (2.8 × 1012 cm−2 eV−1), small gate leakage current (2.67 × 10−5 A cm−2 at Vg = Vfb + V), and large dielectric constant (25.8). The involved mechanisms may originate from the decrease in the interface state density and the increase in the conduction band offset. The appropriate band offset relative to GaAs and excellent interface properties render HfTiON/GaAs as promising gate stacks in future III–V-based devices.
Co-reporter:Gang He, Juan Gao, Hanshuang Chen, Jingbiao Cui, Zhaoqi Sun, and Xiaoshuang Chen
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 24) pp:22013
Publication Date(Web):December 4, 2014
DOI:10.1021/am506351u
In current work, the effect of the growth cycles of atomic-layer-deposition (ALD) derived ultrathin Al2O3 interfacial passivation layer on the interface chemistry and electrical properties of MOS capacitors based on sputtering-derived HfTiO as gate dielectric on InGaAs substrate. Significant suppression of formation of Ga–O and As–O bond from InGaAs surface after deposition of ALD Al2O3 with growth cycles of 20 has been achieved. X-ray photoelectron spectroscopy (XPS) measurements have confirmed that suppressing the formation of interfacial layer at HfTiO/InGaAs interface can be achieved by introducing the Al2O3 interface passivation layer. Meanwhile, increased conduction band offset and reduced valence band offset have been observed for HfTiO/Al2O3/InGaAs gate stack. Electrical measurements of MOS capacitor with HfTiO/Al2O3/InGaAs gate stacks with dielectric thickness of ∼4 nm indicate improved electrical performance. A low interface-state density of (∼1.9) × 1012 eV–1 cm–2 with low frequency dispersion ( ∼ 3.52%), small border trap density of 2.6 × 1012 cm–2, and low leakage current of 1.17 × 10–5 A/cm2 at applied gate voltage of 1 V have been obtained. The involved leakage current conduction mechanisms for metal-oxide-semiconductor (MOS) capacitor devices with and without Al2O3 interface control layer also have been discussed in detail.Keywords: atomic-layer-deposition; electrical properties; high-k gate dielectric; metal-oxide-semiconductor; surface passivation
Co-reporter:H.H. Wei, G. He, X.S. Chen, J.B. Cui, M. Zhang, H.S. Chen, Z.Q. Sun
Journal of Alloys and Compounds 2014 Volume 591() pp:240-246
Publication Date(Web):5 April 2014
DOI:10.1016/j.jallcom.2013.12.152
•Al2O3/HfO2/Al2O3 gate stacks has been deposited on Si substrate by ALD.•Interface thermal stability related with annealing temperature has been studied.•Phase separation at 700 °C and silicate formation at 900 °C have been detected.Based on X-ray photoelectron spectroscopy (XPS) and oxygen energy loss spectra, influences of vacuum annealing temperature on the interfacial thermal stability and band alignment of Al2O3/HfO2/Al2O3/Si gate stacks deposited by atomic layer deposition has been investigated. It has been revealed that annealing the multilayered Al2O3/HfO2/Al2O3 structure from 500 to 600 °C leads to the formation of the composited Hf–Al–O alloy thin film. Meanwhile, phase separation of Hf–Al–O into HfO2 and Al2O3 for samples annealed at 700 °C and silicate formation for sample annealed at 900 °C has been observed. The band profiles, obtained via oxygen energy loss spectroscopy, provided us some insight, which is both convenient and at the same time important, into the way to identify high-k dielectric materials, and we also found that Al2O3/HfO2/Al2O3/Si gate stacks annealing at suitable temperature range of 500–700 °C could be a promising candidate for high-k gate dielectrics.
Co-reporter:Gang He, Toyohiro Chikyow, Xiaoshuang Chen, Hanshuang Chen, Jiangwei Liu and Zhaoqi Sun
Journal of Materials Chemistry A 2013 vol. 1(Issue 2) pp:238-245
Publication Date(Web):22 Oct 2012
DOI:10.1039/C2TC00012A
GaN films with single-crystalline and polycrystalline structures were deposited by metalorganic chemical vapor deposition (MOCVD) on (111) and (100) MgAl2O4 substrates modified by chemical etching and thermal passivation. The oriented GaN films on the as-processed (111) MgAl2O4 substrate revealed broad visible emission band bands at 3.2 eV and a sharp luminescence peak centered at 1.8 eV in room temperature cathodoluminescence measurements, which can be attributed to the recombination of donor–acceptor pairs and GaN-related emission, respectively. Field emission (FE) measurements demonstrated that the oriented nanostructured 150 nm-thick GaN film on the as-processed (111) MgAl2O4 substrate has an ultralow turn-on-field of 4.29 V μm−1 at 10 nA cm−2 and a stable emission of 0.028 mA cm−2 with 5% current density fluctuation for 22 h without any degradation. Compared to GaN films on as-processed (100) MgAl2O4 substrate, the mechanism for the improved performance in optical and FE properties of the GaN film on as-processed (111) MgAl2O4 substrate has been investigated in detail.
Co-reporter:Gang He, Xiaoshuang Chen, Zhaoqi Sun
Surface Science Reports 2013 Volume 68(Issue 1) pp:68-107
Publication Date(Web):1 March 2013
DOI:10.1016/j.surfrep.2013.01.002
Recently, III–V materials have been extensively studied as potential candidates for post-Si complementary metal-oxide-semiconductor (CMOS) channel materials. The main obstacle to implement III–V compound semiconductors for CMOS applications is the lack of high quality and thermodynamically stable insulators with low interface trap densities. Due to their excellent thermal stability and relatively high dielectric constants, Hf-based high-k gate dielectrics have been recently highlighted as the most promising high-k dielectrics for III–V-based devices. This paper provides an overview of interface engineering and chemistry of Hf-based high-k dielectrics on III–V substrates. We begin with a survey of methods developed for generating Hf-based high-k gate dielectrics. To address the impact of these hafnium based materials, their interfaces with GaAs as well as a variety of semiconductors are discussed. After that, the integration issues are highlighted, including the development of high-k deposition without Fermi level pinning, surface passivation and interface state, and integration of novel device structure with Si technology. Finally, we conclude this review with the perspectives and outlook on the future developments in this area. This review explores the possible influences of research breakthroughs of Hf-based gate dielectrics on the current and future applications for nano-MOSFET devices.
Co-reporter:J.J. Wang, Z.B. Fang, T. Ji, W.Y. Ren, Y.Y. Zhu, G. He
Applied Surface Science 2012 Volume 258(Issue 16) pp:6107-6110
Publication Date(Web):1 June 2012
DOI:10.1016/j.apsusc.2012.03.013
Abstract
Tm2O3 crystalline films have been deposited on Si (0 0 1) by molecular beam epitaxy (MBE). Band alignments of Tm2O3/Si gate stacks were studied by X-ray photoelectron spectroscopy (XPS). According to XPS measurements, it can be noted that a valence-band offset of −3.1 ± 0.1 eV and a conduction-band offset of 2.3 ± 0.3 eV for the Tm2O3/Si heterojunction have been obtained. Based on analysis from O 1s energy-loss spectrum, the energy gap of Tm2O3 is determined to be 6.5 ± 0.3 eV. A relatively thicker interfacial SiOx layer was observed for the as-annealed samples. However, no apparent change in band alignment has been observed for Tm2O3/Si heterojunction with the formation of interface layer, which has been discussed in detail.
Co-reporter:Gang He, Liqiang Zhu, Zhaoqi Sun, Qing Wan, Lide Zhang
Progress in Materials Science 2011 Volume 56(Issue 5) pp:475-572
Publication Date(Web):July 2011
DOI:10.1016/j.pmatsci.2011.01.012
Due to the limitations in conventional complementary metal–oxide–semiconductor (CMOS) scaling technology in recent years, innovation in transistor structures and integration of novel materials has been a key to enhancing the performance of CMOS field-effect transistors (FETs) of past technology generations. Tremendous progress of high dielectric constant (high-k) gate stacks has been made in recent years and some of them have come into application in CMOS devices. However, many challenges remain, such as: (a) suitable permittivity, band gap and band alignment for dielectrics, on Si, (b) thermodynamic stability and interface engineering at both high-k/Si interface and metal/metal interface, (c) depletion effect, high gate resistance and its incompatibility with high-k for metal gate, and (d) low performance attributed to threshold voltage instability. Based on current progress and fundamental considerations, we review the current status and challenges in novel high-k dielectrics and metal gates research for planar CMOS devices and alternative device technologies to provide insights for future research. Finally, this review concludes with perspectives towards the future gate stack technology and challenges in advanced CMOS devices.
Co-reporter:S.S. Jiang, G. He, S. Liang, L. Zhu, W.D. Li, C.Y. Zheng, J.G. Lv, M. Liu
Journal of Alloys and Compounds (15 May 2017) Volume 704() pp:322-328
Publication Date(Web):15 May 2017
DOI:10.1016/j.jallcom.2017.02.051
Co-reporter:P. Jin, G. He, Z.B. Fang, M. Liu, D.Q. Xiao, J. Gao, S.S. Jiang, W.D. Li, Z.Q. Sun, M. Zhang
Ceramics International (15 February 2017) Volume 43(Issue 3) pp:
Publication Date(Web):15 February 2017
DOI:10.1016/j.ceramint.2016.11.120
Deposition of HfAlOx gate dielectric films on n-type Si and quartz substrates by sol-gel technique has been performed and the optical, electrical characteristics of the as-deposited HfAlOx thin films as a function of annealing temperature have been investigated. The optical properties of HfAlOx thin films related to annealing temperature are investigated by ultraviolet-visible spectroscopy (UV–vis) and spectroscopy ellipsometry (SE). By measurement of UV–vis, average transmission of all the HfAlOx samples are about 85% owing to their uniform composition. And the increase in band gap has been observed with the increase of annealing temperature. Moreover, the increase of refractive index (n) and density with the increase of annealing temperature are obtained by SE measurements. Additionally, the electrical properties based on Al/Si/HfAlOx/Al capacitor are analyzed by means of the high frequency capacitance-voltage (C-V) and the leakage current density-voltage (J-V) characteristics. Results have shown that 400 °C-annealed sample demonstrates good electrical performance, including larger dielectric constant of 12.93 and lower leakage current density of 3.75×10−7 A/cm2 at the gate voltage of 1 V. Additionally, the leakage current conduction mechanisms as functions of annealing temperatures are also discussed systematically.
Co-reporter:Gang He, Jiangwei Liu, Hanshuang Chen, Yanmei Liu, Zhaoqi Sun, Xiaoshuang Chen, Mao Liu and Lide Zhang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 27) pp:NaN5308-5308
Publication Date(Web):2014/04/17
DOI:10.1039/C4TC00572D
Effects of nitrogen incorporation on the interface chemical bonding states, optical dielectric function, band alignment, and electrical properties of sputtering-derived HfTiO high-k gate dielectrics on GaAs substrates have been studied by angle resolved X-ray photoemission spectroscopy (ARXPS), spectroscopy ellipsometry (SE), and electrical measurements. XPS analysis has confirmed that the interfacial layer of a HfTiO/GaAs gate stack is suppressed effectively after nitrogen incorporation. Analysis by SE has confirmed that reduction in band gap and increase in refractive index are observed with the incorporation of nitrogen. Reduction in valence band offset and increase in conduction band offset have been observed for a HfTiON/GaAs gate stack. Electrical measurements based on metal-oxide-semiconductor (MOS) capacitors have shown that the MOS capacitor with a HfTiON/GaAs stacked gate dielectric annealed at 600 °C exhibits low interface-state density (2.8 × 1012 cm−2 eV−1), small gate leakage current (2.67 × 10−5 A cm−2 at Vg = Vfb + V), and large dielectric constant (25.8). The involved mechanisms may originate from the decrease in the interface state density and the increase in the conduction band offset. The appropriate band offset relative to GaAs and excellent interface properties render HfTiON/GaAs as promising gate stacks in future III–V-based devices.
Co-reporter:Gang He, Toyohiro Chikyow, Xiaoshuang Chen, Hanshuang Chen, Jiangwei Liu and Zhaoqi Sun
Journal of Materials Chemistry A 2013 - vol. 1(Issue 2) pp:NaN245-245
Publication Date(Web):2012/10/22
DOI:10.1039/C2TC00012A
GaN films with single-crystalline and polycrystalline structures were deposited by metalorganic chemical vapor deposition (MOCVD) on (111) and (100) MgAl2O4 substrates modified by chemical etching and thermal passivation. The oriented GaN films on the as-processed (111) MgAl2O4 substrate revealed broad visible emission band bands at 3.2 eV and a sharp luminescence peak centered at 1.8 eV in room temperature cathodoluminescence measurements, which can be attributed to the recombination of donor–acceptor pairs and GaN-related emission, respectively. Field emission (FE) measurements demonstrated that the oriented nanostructured 150 nm-thick GaN film on the as-processed (111) MgAl2O4 substrate has an ultralow turn-on-field of 4.29 V μm−1 at 10 nA cm−2 and a stable emission of 0.028 mA cm−2 with 5% current density fluctuation for 22 h without any degradation. Compared to GaN films on as-processed (100) MgAl2O4 substrate, the mechanism for the improved performance in optical and FE properties of the GaN film on as-processed (111) MgAl2O4 substrate has been investigated in detail.
