Co-reporter:Lu Gan, Jing Li, Zhishan Fang, Haiping He, and Zhizhen Ye
The Journal of Physical Chemistry Letters October 19, 2017 Volume 8(Issue 20) pp:5177-5177
Publication Date(Web):September 29, 2017
DOI:10.1021/acs.jpclett.7b02083
In recent years, 2D layered organic–inorganic lead halide perovskites have attracted considerable attention due to the distinctive quantum confinement effects as well as prominent excitonic luminescence. Herein, we show that the recombination dynamics and photoluminescence (PL) of the 2D layered perovskites can be tuned by the organic cation length. 2D lead iodide perovskite crystals with increased length of the organic chains reveal blue-shifted PL as well as enhanced relative internal quantum efficiency. Furthermore, we provide experimental evidence that the formation of face-sharing [PbI6]4– octahedron in perovskites with long alkyls induces additional confinement for the excitons, leading to 1D-like recombination. As a result, the PL spectra show enhanced inhomogeneous broadening at low temperature. Our work provides physical understanding of the role of organic cation in the optical properties of 2D layered perovskites, and would benefit the improvement of luminescence efficiency of such materials.
Co-reporter:Junjie Si;Jing Li;Lu Gan;Yang Liu;Haiping He
ACS Applied Materials & Interfaces December 7, 2016 Volume 8(Issue 48) pp:32978-32983
Publication Date(Web):November 8, 2016
DOI:10.1021/acsami.6b13289
Organo-lead halide perovskite has emerged as a promising optical gain media. However, continuous efforts are needed to improve the amplified spontaneous emission (ASE) even lasing properties to evade the poor photostability and thermal instability of the perovskites. Herein, we report that simply through the coating of polymer layer, the CH3NH3PbBr3 polycrystalline films prepared by a modified sequential deposition process show remarkably enhanced photoluminescence and prolonged decay lifetime. As a result, under nanosecond pulse pumping, the ASE threshold of the perovskite films is significantly reduced from 303 to 140 μJ/cm2. Furthermore, the light exposure stability is improved greatly after the polymer coating. We confirmed that the polymer layer plays the roles of both surface passivation and symmetric waveguides. Our results may shed light upon the stable and sustained output of laser from perovskite materials.Keywords: amplified spontaneous emission; perovskite; surface passivation; thin films; waveguide;
Co-reporter:Zheng Wang, Lu Gan, Haiping He, and Zhizhen Ye
ACS Applied Materials & Interfaces April 19, 2017 Volume 9(Issue 15) pp:13537-13537
Publication Date(Web):March 30, 2017
DOI:10.1021/acsami.7b02425
Monolayer ZnO represents a class of new two-dimensional (2D) materials that are expected to exhibit unique optoelectronic properties and applications. Here we report a novel strategy to synthesize free-standing atomically thin ZnO layers via the oxidation of hydrothermally grown ultrathin zinc chalcogenide nanosheets. With micrometer-scaled lateral size, the obtained ultrathin ZnO layer has a thickness of ∼2 nm, and the layered structure still maintained well after high temperature oxidation. The thermal treatment strongly improves the crystal quality as well without inducing cracks or pinholes in the ultrathin layers. The atomically thin ZnO layers are highly luminescent with dominant green emission. High quality white light is obtained from the mixed phosphors containing the ZnO layers, exhibiting their potential as compelling ultraviolet-excited phosphors.Keywords: free-standing; light emission; two-dimensional materials; ZnO;
Co-reporter:Xin Wang;Zhi-zhen Ye;Yi-zheng Jin
Journal of Zhejiang University-SCIENCE A 2017 Volume 18( Issue 4) pp:306-312
Publication Date(Web):2017 April
DOI:10.1631/jzus.A1600399
Alloying is an effective way to manipulate the composition and physico-chemical properties of functional materials. We demonstrated the syntheses of alloyed CoxNi1−xO nanocrystals using a nonaqueous approach, with x continuously tuned from 0 to 1 by varying the molar ratios of the cobalt precursor in the reagents. The morphological, structural, and compositional properties of the alloyed CoxNi1−xO nanocrystals were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and energy dispersive X-ray spectroscopy (EDS). The results showed that the cobalt and nickel atoms were homogeneously distributed in the alloyed nanocrystals. The as-prepared CoxNi1−xO nanocrystals can be applied as the hole-transporting layers in polymer light emitting diodes (PLEDs). Our study provides a good example for the syntheses of alloyed oxide nanocrystals with continuously tunable composition.合成成分连续可调的CoxNi1−xO 合金纳米晶, 揭 示CoxNi1−xO 合金纳米晶的形貌和晶体结构随纳 米晶中钴离子含量的变化规律以及考察金属离 子在合金纳米晶的分布情况。1. 利用金属羧酸盐在有机体系中的醇解反应制备 CoxNi1−xO 合金纳米晶, 其反应温度仅为270 °C, 显著低于文献报道中所使用的温度; 2. 成功实现 CoxNi1−xO 纳米晶成分的调节, 发现纳米晶形貌随 成分的变化规律; 3. 揭示了金属离子在合金纳米 晶中的均匀分布。1. 在硬脂酸锂的“配体保护”作用下, 利用金属 羧酸盐的醇解反应制备CoxNi1−xO 合金纳米晶; 2. 利用透射电子显微镜、X 射线衍射、原子发射 光谱和X 射线光电子等手段研究CoxNi1−xO 合金 纳米晶的形貌、晶体结构、成分和金属离子价态 等信息。1. 成功地制备出高质量的CoxNi1−xO (x∈[0, 1])合 金纳米晶; 2. 发现CoxNi1−xO 合金纳米晶的形貌 和晶体结构随纳米晶中钴离子浓度的提高呈现 出由NiO 特征过渡到CoO 特征的趋势; 3. 对单 颗CoxNi1−xO 合金纳米晶的元素扫描揭示了金属 离子在纳米晶中的均匀分布。
Co-reporter:Xiaoyong Liang;Sai Bai;Xin Wang;Xingliang Dai;Feng Gao;Baoquan Sun;Zhijun Ning;Yizheng Jin
Chemical Society Reviews 2017 vol. 46(Issue 6) pp:1730-1759
Publication Date(Web):2017/03/21
DOI:10.1039/C6CS00122J
Colloidal metal oxide nanocrystals offer a unique combination of excellent low-temperature solution processability, rich and tuneable optoelectronic properties and intrinsic stability, which makes them an ideal class of materials as charge transporting layers in solution-processed light-emitting diodes and solar cells. Developing new material chemistry and custom-tailoring processing and properties of charge transporting layers based on oxide nanocrystals hold the key to boosting the efficiency and lifetime of all-solution-processed light-emitting diodes and solar cells, and thereby realizing an unprecedented generation of high-performance, low-cost, large-area and flexible optoelectronic devices. This review aims to bridge two research fields, chemistry of colloidal oxide nanocrystals and interfacial engineering of optoelectronic devices, focusing on the relationship between chemistry of colloidal oxide nanocrystals, processing and properties of charge transporting layers and device performance. Synthetic chemistry of colloidal oxide nanocrystals, ligand chemistry that may be applied to colloidal oxide nanocrystals and chemistry associated with post-deposition treatments are discussed to highlight the ability of optimizing processing and optoelectronic properties of charge transporting layers. Selected examples of solution-processed solar cells and light-emitting diodes with oxide-nanocrystal charge transporting layers are examined. The emphasis is placed on the correlation between the properties of oxide-nanocrystal charge transporting layers and device performance. Finally, three major challenges that need to be addressed in the future are outlined. We anticipate that this review will spur new material design and simulate new chemistry for colloidal oxide nanocrystals, leading to charge transporting layers and solution-processed optoelectronic devices beyond the state-of-the-art.
Co-reporter:Xiaoli Peng;Yiyu Zeng;Xinhua Pan;Weihao Wang;Yonghui Zhou;Fengzhi Wang;Qiaoqi Lu
RSC Advances (2011-Present) 2017 vol. 7(Issue 47) pp:29440-29445
Publication Date(Web):2017/06/05
DOI:10.1039/C7RA04966H
Vertical zinc oxide nanorods (ZnO NRs) were grown on a fluorine-doped tin oxide coated glass substrate using a simple hydrothermal method. A novel iodine-free quasi solid-state electrolyte containing 1-methyl-3-propylimidazolium iodide, potassium iodide (KI) and poly(ethylene oxide) (PEO) was prepared. KI acted as a charge transfer auxiliary agent and PEO was used to solidify the liquid electrolyte. A self-powered photoelectrochemical cell type ultraviolet (UV) photodetector was fabricated, using ZnO NRs as the active photoanode and the quasi solid-state electrolyte as the electrolyte. The dependence of the photocurrent on the iodine-free quasi solid-state electrolyte containing different amounts of KI and PEO was investigated in detail. An optimal photocurrent can be obtained when the amount of KI and PEO was up to 0.03 g and 0.2 g, respectively, and the photodetector shows high responsivity (2.33 A W−1) and high sensitivity (533). The performance of the self-powered UV photodetector showed no obvious decay four months later, which shows great stability.
Co-reporter:Yiyu Zeng, Xinhua Pan, Bin Lu and Zhizhen Ye
RSC Advances 2016 vol. 6(Issue 37) pp:31316-31322
Publication Date(Web):17 Mar 2016
DOI:10.1039/C6RA02922A
A flexible self-powered ultraviolet (UV) detector based on ZnO nanowires has been fabricated for the first time. The assembled UV detector shows good performance both in flat and bending conditions, which is important for future wearable and flexible optoelectronic applications. The responsivity of the fabricated device has improved by 44% after the decoration of Ag nanoparticles. Such enhancement is attributed to the modified structure which facilitates light absorption.
Co-reporter:Yilan Chu, Bin Cai, Ye Ma, Minggang Zhao, Zhizhen Ye and Jingyun Huang
RSC Advances 2016 vol. 6(Issue 27) pp:22673-22678
Publication Date(Web):12 Feb 2016
DOI:10.1039/C5RA27625J
By integrating thin-layer molybdenum disulfide (MoS2) and graphene through a hydrothermal process and an ultrasonic method, a label-free, amplification-free and ultrasensitive circulating tumor DNA electrochemical sensor was made. Compared with other methods, this preparation process was simpler and the electrochemical properties were enhanced. Using a differential pulse voltammetry test, this sensor can detect trace amounts of DNA in the range from 10−16 M to 10−13 M. Compared with other methods that are used to detect the same circulating tumor DNA, this sensor has an obvious advantage in sensitivity, cost and simplicity because it removes the need for labelling processes and amplifiers.
Co-reporter:Mu Xiao, Yaguang Li, Yangfan Lu and Zhizhen Ye
Journal of Materials Chemistry A 2015 vol. 3(Issue 6) pp:2701-2706
Publication Date(Web):03 Dec 2014
DOI:10.1039/C4TA05931J
In this paper, the ZrO2:Fe nanostructures with precisely controlled Fe doping contents are obtained by using a template method. The characterizations obviously show that the as-prepared samples have hollow sphere-like morphology and high crystalline quality. Furthermore, the band gap of the ZrO2:Fe nanostructures is facilely tunable by controlling the Fe content. In addition, the density-functional theory (DFT) calculation reveals that the formation of an impurity band in the band gap narrows the band gap of the Fe-doped ZrO2 nanostructures. The visible-light driven photocatalytic activity of ZrO2 nanostructures could be remarkably enhanced by doping the Fe impurity. This can be attributed to the red shift of the absorption edge and the trapping effect of the ZrO2:Fe nanostructures. The research results provide a general and effective method to synthesize different photocatalysts with enhanced visible-light driven H2 evolution activity.
Co-reporter:Yiyu Zeng, Xinhua Pan, Wen Dai, Yunchao Chen and Zhizhen Ye
RSC Advances 2015 vol. 5(Issue 82) pp:66738-66741
Publication Date(Web):24 Jul 2015
DOI:10.1039/C5RA08187D
A self-powered photoelectrochemical cell-type UV detector has been fabricated using Ag nanoparticle-modified ZnO NWs as an active photoanode and H2O as the electrolyte. The fabricated device shows a high responsivity (0.37 A W−1). The enhancement is attributed to the modification of the structure which enables more effective separation and directional transfer.
Co-reporter:Wen Dai, Xinhua Pan, Shanshan Chen, Cong Chen, Wei Chen, Honghai Zhang and Zhizhen Ye
RSC Advances 2015 vol. 5(Issue 9) pp:6311-6314
Publication Date(Web):08 Dec 2014
DOI:10.1039/C4RA13205J
A ZnO homojunction UV photodetector based on Sb-doped p-type ZnO nanorods (NRs) and n-type ZnO NRs was fabricated by a low temperature solution method. The fabricated homojunction shows well-defined rectifying characteristics, confirming the p-type conductivity of the Sb-doped ZnO NRs. Moreover, a high UV sensitivity of 3300% and a fast reset time to UV illumination are also achieved.
Co-reporter:Cholho Jang, Qingjun Jiang, Jianguo Lu, Zhizhen Ye
Journal of Materials Science & Technology 2015 Volume 31(Issue 11) pp:1108-1110
Publication Date(Web):November 2015
DOI:10.1016/j.jmst.2015.07.018
Ga doped ZnO (GZO)/Cu grid/GZO transparent conductive electrode (TCE) structures were fabricated at room temperature (RT) by using electron beam evaporation (EBE) for the Cu grids and RF magnetron sputtering for the GZO layers. In this work, we investigated the electrical and optical characteristics of GZO/Cu grid/GZO multilayer electrode for thin film solar cells by using evaporated Cu grid and sputtered GZO thin films to enhance the optical transparency without significantly affecting their conductivity. The optical transmittance and sheet resistance of GZO/Cu grid/GZO multilayer are higher than those of GZO/Cu film/GZO multilayer independent of Cu grid separation distance and increase with increasing Cu grid separation distances. The calculation of both transmittance and sheet resistance of GZO/Cu grid/GZO multilayer was based on Cu filling factor correlated with the geometry of Cu grid. The calculated values for the transmittance and sheet resistance of the GZO/Cu grid/GZO multilayer were similar to the experimentally observed ones. The highest figure of merit ΦTC is 5.18 × 10−3 Ω−1 for the GZO/Cu grid/GZO multilayer with Cu grid separation distance of 1 mm was obtained, in this case, the transmittance and resistivity were 82.72% and 2.17 × 10−4 Ω cm, respectively. The transmittance and resistivity are acceptable for practical thin film solar cell applications.
Co-reporter:Cholho Jang, Zhizhen Ye, Qingjun Jiang
Materials Science in Semiconductor Processing 2015 30() pp: 152-156
Publication Date(Web):
DOI:10.1016/j.mssp.2014.09.024
Co-reporter:Cong Chen, Wen Dai, Yangfan Lu, Haiping He, Qiaoqi Lu, Tao Jin, Zhizhen Ye
Materials Research Bulletin 2015 70() pp: 190-194
Publication Date(Web):
DOI:10.1016/j.materresbull.2015.04.040
Co-reporter:Wen Dai, Xinhua Pan, Shanshan Chen, Cong Chen, Zhen Wen, Honghai Zhang and Zhizhen Ye
Journal of Materials Chemistry A 2014 vol. 2(Issue 23) pp:4606-4614
Publication Date(Web):19 Mar 2014
DOI:10.1039/C4TC00157E
Honeycomb-like NiO/ZnO heterostructured nanorods (NRs) were fabricated by a simple photochemical deposition method. The morphology of the NiO nanostructures can be rationally tailored by changing the concentration of the solution, reaction time and annealing temperature. A reasonable formation mechanism of the honeycomb-like NiO/ZnO NRs is proposed, which is closely related to the production of OH− in the vicinity of ZnO NRs during the photochemical deposition process. The fabricated NiO/ZnO p–n heterojunction shows a well-defined rectifying characteristic with a turn-on voltage of 0.66 V and a negligible leakage current. Moreover, the UV detection performance increases considerably compared to that of bare ZnO NRs, which is attributed to the change of nanostructure and the extended carrier depletion region near p-NiO/n-ZnO junctions.
Co-reporter:Mu Xiao, Yangfan Lu, Yaguang Li, Hui Song, Liping Zhu and Zhizhen Ye
RSC Advances 2014 vol. 4(Issue 65) pp:34649-34653
Publication Date(Web):02 Jul 2014
DOI:10.1039/C4RA04600E
A new type of NiO/ZnO nano-heterojunction was developed by the template-assisted approach. The p–n nano-heterojunctions were formed between the NiO and ZnO nanoparticles in the ultrathin shell of the NiO/ZnO hollow nanospheres. The grain size of the NiO/ZnO nano-heterojunctions is in the 10 nm scale, and the specific surface area is higher than 100 m2 g−1. Moreover, the ultrathin shell makes the distribution of the NiO/ZnO nano-heterojunctions to arrange in a single-layer structure rather than a stacking arrangement. Therefore, this new type of the NiO/ZnO nano-heterojunctions could almost completely separate the electron and hole to the surface rather than being wasted in the materials. As a result, the photocatalytic activity of the p-type NiO/n-type ZnO nano-heterojunctions for the degradation of rhodamine B (RhB) was much higher than that of ZnO. In particular, the p-type NiO/n-type ZnO hollow nanospheres with different Ni/Zn molar ratios exhibited diverse catalytic activity, the mechanism of which has been discussed in detail.
Co-reporter:Jie Zhang, Xifeng Li, Jianguo Lu, Nanjia Zhou, Peijun Guo, Bin Lu, Xinhua Pan, Linxiang Chen and Zhizhen Ye
RSC Advances 2014 vol. 4(Issue 7) pp:3145-3148
Publication Date(Web):23 Oct 2013
DOI:10.1039/C3RA44513E
Stability of amorphous InAlZnO thin-film transistors was investigated under vacuum conditions and an oxygen atmosphere with different rates of relative humidity. The mechanism of water assisted oxygen absorption on the back channel is proposed to explain the phenomenon that wet oxygen leads to a larger positive threshold voltage (Vth) shift than dry oxygen.
Co-reporter:Wen Dai, Xinhua Pan, Cong Chen, Shanshan Chen, Wei Chen, Honghai Zhang and Zhizhen Ye
RSC Advances 2014 vol. 4(Issue 60) pp:31969-31972
Publication Date(Web):09 Jul 2014
DOI:10.1039/C4RA04249B
A compact Cu-doped ZnO nanorod (NR) array film was synthesized by a facile hydrothermal method and post-annealing process. The obtained ZnO NR array film-based UV photodetectors exhibit not only enhanced UV sensitivity but also faster reset time compared to undoped ZnO NR samples, which are attributed to the trapping and de-trapping of electrons by Cu-related defects.
Co-reporter:H.H. Zhang, X.H. Pan, H.P. He, W. Chen, J.Y. Huang, P. Ding, B. Lu, Z.Z. Ye, J.G. Lu, L.X. Chen, C.L. Ye
Optics Communications 2014 Volume 318() pp:37-40
Publication Date(Web):1 May 2014
DOI:10.1016/j.optcom.2013.12.045
Temperature-dependent photoluminescence (PL) measurements are used to study two ZnO/Zn1−xMgxO multiple quantum well (MQW) structures with different barrier compositions. The PL band in the well layers is dominated by localized excitons (LEs), free excitons (FEs), and two longitudinal optical (LO) phonon replicas of the LE emission. The LE emission of higher Mg compositional barrier exhibits a significant blue shift of about 70 meV with respect to the lower one. The mechanisms of carrier dynamics and localization are investigated within the temperature range 14–300 K. As the temperature increases, luminescence from the excitons localized in the well layers shows an ‘S-shaped’ shift in the high-barrier MQWs, whereas a monotonic red shift is observed in the low-barrier MQWs. The ‘S-shaped’ shift behavior is associated with delocalization of the excitons in the potential minima induced by interface fluctuations or alloy disorder. Large exciton binding energies of 64 and 76 meV were deduced, demonstrating efficient quantum confinement in the ZnO/ZnMgO MQWs.
Co-reporter:Minggang Zhao, Bin Cai, Ye Ma, Hi Cai, Jingyun Huang, Xinhua Pan, Haiping He, Zhizhen Ye
Biosensors and Bioelectronics 2014 Volume 61() pp:443-447
Publication Date(Web):15 November 2014
DOI:10.1016/j.bios.2014.05.051
•The hierarchical hollow microspheres are assembled to self-supporting architecture.•The branches can afford transport channels and improve the kinetic performance.•The hierarchical microspheres act as functional cell for immobilizing biomolecule.•Assembling microspheres to ordered architecture enhances the biosensing performance.•This architecture can be used for fabricating high performance biosensors.We demonstrate a facile and scalable approach to fabricate and self-assemble the hierarchical hollow microspheres into self-supporting architecture by naturally grown branches. The supporting branches can afford integrated transport channels and significantly improve the kinetic performance and mechanical stability. Meanwhile, the supported hierarchical microspheres acting as functional cell can provide high active sites, multiple response and suitable environment for immobilizing biomolecules. Different enzymes are immobilized for biosensors. The experiments demonstrate that the effective assembly of hierarchical microspheres into large size ordered architecture by self-supporting branches can significantly enhance the biosensing performance.
Co-reporter:Yefeng Yang, Yaguang Li, Liping Zhu, Haiping He, Liang Hu, Jingyun Huang, Fengchun Hu, Bo He and Zhizhen Ye
Nanoscale 2013 vol. 5(Issue 21) pp:10461-10471
Publication Date(Web):27 Aug 2013
DOI:10.1039/C3NR03160H
For colloidal semiconductor nanocrystals (NCs), shape control and doping as two widely applied strategies are crucial for enhancing and manipulating their functional properties. Here we report a facile and green synthetic approach for high-quality colloidal Mn doped ZnO NCs with simultaneous control over composition, shape and optical properties. Specifically, the shape of doped ZnO NCs can be finely modulated from three dimensional (3D) tetrapods to 0D spherical nanoparticles in a single reaction scheme. The growth mechanism of doped ZnO NCs with interesting shape transition is explored. Furthermore, we demonstrate the tunable optical absorption features of Mn doped ZnO NCs by varying the Mn doping levels, and the enhanced photocatalytic performance of Mn doped ZnO NCs under visible light, which can be further optimized by delicately controlling their shapes and Mn doping concentrations. Our results provide an improved understanding of the growth mechanism of doped NCs during the growth process and can be potentially extended to ZnO NCs doped with other metal ions for various applications.
Co-reporter:Cong Chen, Yangfan Lu, Haiping He, Mu Xiao, Zheng Wang, Lingxiang Chen, and Zhizhen Ye
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 20) pp:10274
Publication Date(Web):September 25, 2013
DOI:10.1021/am403133u
Violet photoluminescence was observed in high-energy hydrogen-plasma-treated ZnO nanorods at 13 K. The photoluminescence spectrum is dominated by a strong violet emission and a shoulder attributed to excitonic emission. The violet emission shows normal thermal behavior with an average lifetime of about 1 μs at 13 K. According to the time-resolved and excitation density-dependent photoluminescence, it was found that the violet emission is determined by at least two emitting channels, which was confirmed by annealing experiments. Evidence was also given that the violet emission is related to hydrogen. We suggested that the hydrogen-related complex defects formed under high-energy hydrogen plasma treatment are responsible for this violet emission.Keywords: hydrogen plasma; hydrogen-related complex defects; photoluminescence; TRPL; violet emission; ZnO nanorods;
Co-reporter:Minggang Zhao, Jingyun Huang, Yu Zhou, Xinhua Pan, Haiping He, Zhizhen Ye and Xiaoqing Pan
Chemical Communications 2013 vol. 49(Issue 69) pp:7656-7658
Publication Date(Web):01 Jul 2013
DOI:10.1039/C3CC43154A
Controlled synthesis of spinel ZnFe2O4 nanoparticle-decorated ZnO nanofiber heterostructures was carried out with regularly varied particle sizes and uniform distribution. The obtained heterostructures possessed enhanced intrinsic peroxidase-like activity, and the activities regularly changed as the sizes of ZnFe2O4 nanoparticles varied. The heterostructures were further applied in sensitive colorimetric biosensing of urine glucose.
Co-reporter:H. H. Zhang, X. H. Pan, B. Lu, J. Y. Huang, P. Ding, W. Chen, H. P. He, J. G. Lu, S. S. Chen and Z. Z. Ye
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 27) pp:11231-11235
Publication Date(Web):22 May 2013
DOI:10.1039/C3CP51156A
The valence band offsets (ΔEV) of Zn1−xMgxO/ZnO heterojunctions grown by plasma-assisted molecular beam epitaxy were measured by photoelectron spectroscopy. From the directly obtained ΔEV values, the related conduction band offsets (ΔEC) were deduced. All the Zn1−xMgxO/ZnO heterojunctions exhibit a type-I band alignment with the ΔEC/ΔEV estimated to be 1.5, 1.8, 2.0 for x = 0.10, 0.15 and 0.20, respectively. The band offsets of Zn1−xMgxO/ZnO heterojunctions depend on Mg composition. The accurate determination of energy band alignment of Zn1−xMgxO/ZnO is helpful for designing ZnO based optoelectronic devices.
Co-reporter:H.H. Zhang, X.H. Pan, P. Ding, J.Y. Huang, H.P. He, W. Chen, B. Lu, J.G. Lu, S.S. Chen, Z.Z. Ye
Applied Surface Science 2013 Volume 279() pp:212-215
Publication Date(Web):15 August 2013
DOI:10.1016/j.apsusc.2013.04.071
Highlights
- •
Single-crystalline Zn0.9Mg0.1O films were grown on c-plane sapphire using MBE.
- •
A thin MgO layer and a following low-temperature ZnO layer are used as buffer layers.
- •
The FWHM for the (0 0 0 2) reflection shows an extremely small value of 47 arcsec.
- •
The screw dislocation density is derived to be 4 × 106 cm−2.
- •
All PL peaks show obvious blueshift compared with those of pure ZnO films.
Co-reporter:Y.F. Lu, K.W. Wu, Y.J. Zeng, Z.Z. Ye, J.Y. Huang, L.P. Zhu, B.H. Zhao
Chemical Physics Letters 2013 Volume 582() pp:82-85
Publication Date(Web):4 September 2013
DOI:10.1016/j.cplett.2013.04.026
Highlights•Na-doped ZnO was grown by MOCVD using cyclopentadienyl sodium as the sodium source.•Secondary ion mass spectrometry measurements revealed the existence of Na in the ZnO thin films.•Local STM/STS investigations revealed the p-type conduction induced by Na doping.•The LDOS of the Na-doped ZnO showed spatial distributions at a nanometer scale.Growth of Na-doped ZnO thin films by low-pressure metal–organic chemical vapor deposition method was realized using cyclopentadienylsodium as the sodium source. Secondary ion mass spectrometry measurements revealed the existence of Na in the ZnO thin films. Low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy were used for obtaining local density of states (LDOS) of the Na-doped ZnO thin films at nanometer scale. The local measurements indicated a spatial distribution of the LDOS as well as the conductivity type that could be linked to spatial variations of Na doping level.Graphical abstract
Co-reporter:Honghai Zhang, Xinhua Pan, Ping Ding, Jingyun Huang, Haiping He, Wei Chen, Yang Li, Bin Lu, Jianguo Lu, Zhizhen Ye
Optics Communications 2013 Volumes 301–302() pp:96-99
Publication Date(Web):1 August 2013
DOI:10.1016/j.optcom.2013.03.052
A series of 5-period ZnO/Zn0.9Mg0.1O multiple quantum wells (MQWs) with different well layer thicknesses in the range of 3–10 nm have been fabricated on (0001) sapphire substrates by plasma-assisted molecular beam epitaxy (MBE) with combined MgO and low-temperature ZnO thin film as buffer layers. The good quality of ZnO/Zn0.9Mg0.1O MQWs is evidenced by the observation of readily resolved Pendellösung fringes and the small full-width at half-maximum (FWHM) value of exciton emission as low as 8.3 meV, as well as the observation of high order phonon replicas. The dominated photoluminescence (PL) peak in the MQWs shows a systematic blueshift with decreasing well width, which is consistent with a quantum confinement effect. In order to clarify the thermal quenching behavior of exciton emission in the MQWs, temperature-dependent PL is investigated and the relevant activation energies are calculated.
Co-reporter:Minggang Zhao, Jingyun Huang, Yu Zhou, Qi Chen, Xinhua Pan, Haiping He, Zhizhen Ye
Biosensors and Bioelectronics 2013 Volume 43() pp:226-230
Publication Date(Web):15 May 2013
DOI:10.1016/j.bios.2012.11.041
A novel method of fabricating a free probe type nanoscale biosensor is first demonstrated. A free probe type biosensor based on a single one-dimensional (1D) mesoporous ZnO/Chitosan inorganic–organic hybrid nanostructure is constructed. The as-prepared biosensor exhibited excellent biosensing performance and was stable in solution due to its inorganic–organic hybrid structure. The special mesoporous nanostructure with protuberances favors enzymes loading and enhances electrical communication efficiency. The feasibility of employing a single 1D nanostructure as a separate free nanoprobe for biosensing is demonstrated. This kind of free probe type biosensor will not only provides a new tool for micro-targets detection in microcell and enzymatic studies, but also has the potential to be inserted into single cell or other microorganism for biological studies.Highlights► Single mesoporous ZnO/Chitosan hybrid nanostructure was fabricated. ► Free probe type nanoscale biosensor based nanostructure is demonstrated. ► As-prepared biosensor exhibited excellent biosensing performance and stability. ► This biosensor will provide a new tool for micro-targets detection in microcell and cellular studies.
Co-reporter:Kewei Wu, Haiping He, Yangfan Lu, Jingyun Huang and Zhizhen Ye
Nanoscale 2012 vol. 4(Issue 5) pp:1701-1706
Publication Date(Web):04 Jan 2012
DOI:10.1039/C2NR11773H
Nanostructured ZnO is considered to be a promising building block in the design of nanoscale optoelectronic devices. It usually shows dominant donor-bound exciton (DX) emission at low temperatures. In this study, ZnO nanorods with high crystallinity and optical quality were grown by metal–organic chemical vapor deposition on a-plane sapphire (110) substrates. Dominant free exciton (FX) emission at a low temperature (14 K) was observed by photoluminescence spectroscopy. It was attributed to both the enhancement of the FX emission induced by the high crystalline quality of the nanorods and the suppression of the DX emission induced by hydrogen out-diffusion. The latter reason is believed to be more important from the analysis of the hydrogen distribution in the nanorods through photoluminescence spectroscopy and secondary ion mass spectrometry. A slow cooling process during the deposition is suggested to result in a better optical quality. These results can promote our understanding of the optical properties of ZnO nanostructures.
Co-reporter:Hongwen Huang, Liqiang Zhang, Kewei Wu, Qing Yu, Ru Chen, Hangsheng Yang, Xinsheng Peng and Zhizhen Ye
Nanoscale 2012 vol. 4(Issue 24) pp:7832-7841
Publication Date(Web):23 Oct 2012
DOI:10.1039/C2NR32729E
A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal–ion complexes plays an important role in slowing the release rate of OH− and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous CuO quasi-monocrystalline nanosheets prepared at 25 °C with a thickness of ca. 10 nm and large specific surface area of 80.32 m2 g−1 is investigated intensively. These CuO nanosheets demonstrate a superior catalytic activity for CO oxidation, with features of high CO conversion efficiency (47.77 mmolCO g−1CuO h−1 at 200 °C), which is close to that reported for previously investigated supported-CuO catalysts, and a low apparent activation energy Ea (53.3 kJ mol−1).
Co-reporter:Hongwen Huang, Qing Yu, Yinghui Ye, Peng Wang, Liqiang Zhang, Mingxia Gao, Xinsheng Peng and Zhizhen Ye
CrystEngComm 2012 vol. 14(Issue 21) pp:7294-7300
Publication Date(Web):02 Aug 2012
DOI:10.1039/C2CE25873K
Thin CuO nanowires with a diameter of 7 ± 3 nm, aspect ratio up to 103–104 and specific surface area of 51.08 m2 g−1 were synthesized by shape-reserved transformation from the corresponding thin copper hydroxide nanowires (CHNs) under an appropriate temperature. A topotactic transition of the crystal structure between Cu(OH)2 and CuO occurred. CdO nanowires were also successfully prepared by this synthetic method. Subsequently, thin CuO nanowires/carbon nanotubes (CNTs) interpenetrating networks were prepared from preformed Cu(OH)2 nanowire/CNT interpenetrating networks and these demonstrated a much higher electrochemical performance than that of pure CuO nanowires for lithium ion batteries. When the CNTs were 33.3 wt% of the CuO nanowires/CNTs interpenetrating networks, they gave the best electrochemical performance, including high capacitance as well as good stability.
Co-reporter:Honghai Zhang, Jianguo Lu, Xiaopen Yang, Zhizhen Ye, Jun Huang, Bin Lu, Liang Hu, Yang Li, Yinzhu Zhang and Dehui Li
CrystEngComm 2012 vol. 14(Issue 13) pp:4501-4506
Publication Date(Web):10 Apr 2012
DOI:10.1039/C2CE00001F
Inclined and ordered ZnO nanowire arrays were grown on non-polar ZnO seed layer films via a simple vapor-phase transport method without employing any template or catalysis. ZnO nanowires exhibited two distinctly opposite directions with an inclination angle of about 58° from the plane of substrate. The formation mechanism was proposed to explain the growth behaviors of ZnO nanowires based on structural analysis. The oblique growth was ascribed to the fact that ZnO seed crystals firstly formed at the end of nanostripes of non-polar ZnO (100) seed layer films, while ZnO nanowires with the [0002] orientation were developed from (101) facets of seed crystals by stacking misfit dislocations with a twist angle of 3.6°. Photoluminescence spectra revealed acceptable optical performances for inclined ZnO nanowire arrays. This work offers a novel approach for effective growth of inclined and highly-ordered ZnO nanowires and helps to understand the growth mechanism of inclined ZnO nanowires.
Co-reporter:X.P. Yang, J.G. Lu, H.H. Zhang, Y. Chen, B.T. Kan, J. Zhang, J. Huang, B. Lu, Y.Z. Zhang, Z.Z. Ye
Chemical Physics Letters 2012 Volume 528() pp:16-20
Publication Date(Web):1 March 2012
DOI:10.1016/j.cplett.2012.01.019
Abstract
ZnO nanorod arrays (NRAs) with different Na contents were prepared by thermal evaporation. Sodium pyrophosphate was adopted as the Na source. The Na contents in NRAs were determined by X-ray photoelectron spectra to be 0, 6.1, and 9.4 at.%. X-ray diffraction (XRD) analyses of Na-doped ZnO NRAs were performed in experiment and by first-principle calculation with the assumption of Na substitutions. A couple of typical changes were found in XRD patterns of Na-doped ZnO. The simulation results well agreed with the experimental data, which revealed that Na mainly located at the substitutional sites in Na-doped ZnO NRAs.
Co-reporter:Ping Ding, Xinhua Pan, Jingyun Huang, Bin Lu, Honghai Zhang, Wei Chen, Zhizhen Ye
Materials Letters 2012 Volume 71() pp:18-20
Publication Date(Web):15 March 2012
DOI:10.1016/j.matlet.2011.12.030
Non-polar ZnO thin films were grown on r -plane sapphire substrates by plasma-assisted molecular beam epitaxy. The film is (112−0)oriented (a-plane) as identified by the X-ray diffraction pattern. Structural properties are anisotropic and surfaces of films show stripes running along the ZnO [0001] direction. The nonintentionally doped non-polar ZnO film exhibits weak p-type conductivity with a hole concentration of 1.33 × 1015 cm− 3, a Hall mobility of 18.7 cm2 V− 1 s− 1, and a resistivity of 251.5 Ω·cm, respectively. Near-band-edge emission is dominant in room-temperature photoluminescence while deep level emission is negligible, indicating high optical quality of the p-type non-polar ZnO thin films.Highlights► Non-polar ZnO thin films were grown on r-plane sapphires by plasma-assisted MBE. ► Structural properties are anisotropic and surfaces of films show stripes. ► The nonintentionally doped non-polar ZnO film exhibits weak p-type conductivity. ► Room-temperature PL shows a strong NBE emission and a negligible deep level emission.
Co-reporter:Xinhua Pan, Ping Ding, Haiping He, Jingyun Huang, Bin Lu, Honghai Zhang, Zhizhen Ye
Optics Communications 2012 Volume 285(21–22) pp:4431-4434
Publication Date(Web):1 October 2012
DOI:10.1016/j.optcom.2012.06.059
We investigated structural and optical properties of ZnO thin films grown on (112̄0) a-plane sapphire substrates using plasma-assisted molecular beam epitaxy. Negligible biaxial stress in ZnO thin films is due to the use of (112̄0) a-plane sapphire substrates and slow substrate cooling. The 14 K photoluminescence spectrum shows a blueshift of energy positions compared with ZnO single crystal. A donor with binding energy of 43 meV and an acceptor with binding energy of ∼170 meV are identified by well-resolved photoluminescence spectra. A characteristic emission band at 3.320 eV (so-called A-line) is studied. Based on analysis from photoluminescence spectra, the origin of the A-line, it seems, is more likely an (e, A°) transition, in which defect behaves as an acceptor. The room-temperature photoluminescence is dominated by the FX at 3.307 eV, which is an indication of strongly reduced defect density in ZnO thin films.
Co-reporter:Kewei Wu, Haiping He, Yangfan Lu, Jingyun Huang, Zhizhen Ye
Solid State Communications 2012 Volume 152(Issue 18) pp:1757-1760
Publication Date(Web):September 2012
DOI:10.1016/j.ssc.2012.05.026
We investigate the negative thermal quenching behavior of the 3.338 eV emission in ZnO nanorods. A correlation between the 3.338 eV and the 3.368 eV (surface exciton) emissions is determined from temperature-dependent photoluminescence. The activation energies of the 3.338 eV emission, obtained using an approximated multi-level model, indicate an trap state between the two surface exciton emissions. The present study demonstrates a nondestructive and easy method to understand the surface effects on the optical properties of semiconductor nanostructures.Highlights► Negative thermal quenching of the 3.338 eV emission in ZnO is investigated. ► The activation energies of the 3.338 eV emission are exacted by a multi-level model. ► We attribute this emission as a near-surface structural defect-bound exciton. ► Trap states may exist between different surface exciton centers.
Co-reporter:Haiping He, Yanjie Wang, Jingrui Wang and Zhizhen Ye
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 33) pp:14902-14905
Publication Date(Web):11 Jul 2011
DOI:10.1039/C1CP21527B
Negative thermal quenching of both the excitonic and green emissions is observed in ZnO nanosheets, from which the energy level of surface traps can be extracted based on a model of multi-level transitions. The present study demonstrates a non-destructive and easy method to determine the trap levels in semiconductor nanostructures.
Co-reporter:Luwei Sun, Haiping He, Chao Liu and Zhizhen Ye
CrystEngComm 2011 vol. 13(Issue 19) pp:5807-5812
Publication Date(Web):27 Jul 2011
DOI:10.1039/C1CE05188A
Three-dimensional SiOx nanostructures with various shapes have been prepared by chemical vapor deposition. The sunflower-like SiOx nanostructures provide a chance to probe the growth process. A typical Ga-assisted vapor–liquid–solid (VLS) model is responsible for the incipient SiOx nanostructures, while the growth of their branches is governed by a SiOx self-catalysis mechanism. Elemental analysis unveils the initial stage and evolution of SiOx nanostructure formation. The optical properties of SiOx nanostructures are also investigated.
Co-reporter:Luwei Sun, Haiping He, Chao Liu, Yangfan Lu and Zhizhen Ye
CrystEngComm 2011 vol. 13(Issue 7) pp:2439-2444
Publication Date(Web):01 Feb 2011
DOI:10.1039/C0CE00844C
In this paper, two types of hybrid semiconductors made up of silicon nanowires and ZnO nanostructures, namely Si/ZnO core–shell nanowire arrays and ZnO quantum dots (QDs)-decorated Si nanowire arrays, have been prepared by combining metal-assisted wet-chemical etching and metal–organic chemical vapor deposition (MOCVD). We demonstrate that ZnO QDs and thin ZnO layers can be grown on Si nanowires in a controlled manner by varying growth parameters including working pressure and growth time. Meanwhile, porous silicon and porous Si/ZnO nanowire arrays have also been fabricated. The morphology and optical properties of both hybrid nanostructures have been carefully investigated for their potential applications in nanowire optoelectronics. A quantum confinement effect in ZnO QDs was confirmed by the blue-shifted photoluminescence. Porous Si/ZnO core–shell nanowires display a very broad emission band throughout the entire visible light range.
Co-reporter:Li Gong, Jianguo Lu, Zhizhen Ye
Solar Energy Materials and Solar Cells 2011 95(7) pp: 1826-1830
Publication Date(Web):
DOI:10.1016/j.solmat.2011.02.004
Co-reporter:Wei-Guang Zhang, Bin Lu, Li-Qiang Zhang, Jian-Guo Lu, Min Fang, Ke-Wei Wu, Bing-Hui Zhao, Zhi-Zhen Ye
Thin Solid Films 2011 Volume 519(Issue 19) pp:6624-6628
Publication Date(Web):29 July 2011
DOI:10.1016/j.tsf.2011.04.233
Fe-doped and Fe–Ga co-doped ZnO diluted magnetic semiconductor thin films on quartz substrate were studied. Rapid annealing enhanced the ferromagnetism (FM) of the films grown in Ar/O2. All the films grown in Ar are n-type and the carrier concentration could increase significantly when Ga is doped. The state of Fe in the films was investigated exhibiting Fe3+. Magnetic measurements revealed that room temperature ferromagnetism in the films were doping concentration dependent and would enhance slightly with Ga doping. The origin of the observed FM is interpreted by the overlapping of polarons mediated through oxygen vacancy based on the bound magnetic polaron model.
Co-reporter:Haiping He ; Shisheng Lin ; Guodong Yuan ; Liqiang Zhang ; Wenfeng Zhang ; Linbao Luo ; Yulin Cao ; Zhizhen Ye ;Shuit Tong Lee
The Journal of Physical Chemistry C 2011 Volume 115(Issue 39) pp:19018-19022
Publication Date(Web):August 9, 2011
DOI:10.1021/jp205807g
The p-type doping of ZnO is the key to ZnO-based light-emitting devices and has proven to be difficult. ZnO nanowires (NWs) are an ideal platform for the study of p-type doping due to their high crystal quality and easy growth. In this Article, we demonstrate an innovative approach via the combination of thin-film and nano techniques to fabricate single-crystal p-type ZnO and ZnMgO NWs. Using undoped ZnO NWs as templates, Na-doped ZnO and ZnMgO layers are deposited by pulsed laser deposition, forming core–shell NWs. Single NW field effect transistors are fabricated to testify the p-type conductivity. It is found that postannealing is crucial to activate the Na acceptor. The present method offers better controllability and reproducibility for fabricating p-type ZnO layers, which are advantageous for optoelectronic applications.
Co-reporter:Yefeng Yang, Yizheng Jin, Haiping He, Qingling Wang, Yao Tu, Huanming Lu, and Zhizhen Ye
Journal of the American Chemical Society 2010 Volume 132(Issue 38) pp:13381-13394
Publication Date(Web):September 8, 2010
DOI:10.1021/ja103956p
The electrical, optical and other important properties of colloidal nanocrystals are determined mainly by the crystals’ chemical composition, size and shape. The introduction of specific dopants is a general approach of modifying the properties of such nanocrystals in well-controlled ways. Here we show that in addition to altering the atomic composition of the nanocrystals the introduction of specific dopants can also lead to dramatic changes in morphology. The creation of Mg-doped ZnO nanocrystals provides an excellent example of this procedure; depending on the molar ratio of dopant precursor in the reagents, doped nanocrystals with well-defined shapes, from tetrapods to ultrathin nanowires, which exhibit tunable optoelectronic properties, are obtained for the first time. We find that the Mg dopants play an important role in the primary growth stage, resulting in initial growth seeds having diverse crystallographic structures, which are critical for the generation of doped nanocrystals with different shapes. We demonstrate that this “greener” synthetic scheme can be extended to other dopant systems and provides an attractive and effective strategy for fabricating doped ZnO nanocrystals with interesting compositional and spatial complexity.
Co-reporter:Y.F. Lu, Z.Z. Ye, Y.J. Zeng, L.P. Zhu, J.Y. Huang, B.H. Zhao
Solid-State Electronics 2010 Volume 54(Issue 7) pp:732-735
Publication Date(Web):July 2010
DOI:10.1016/j.sse.2010.03.012
Low-resistivity Ni/Pt Ohmic contacts to p-type N-doped ZnO were fabricated in this paper. Ni/Pt Ohmic contacts showed a lowest specific contact resistivity of 3.81 × 10−6 Ω cm2 after 450 °C annealing, which is lower than any other reported Ohmic contacts to p-type ZnO. The interface reactions during annealing and the Ohmic contact formation mechanism were investigated by secondary ion mass spectrometry measurements. The results showed that Ni out-diffused to react with Pt and Zn out-diffused a little, too. These interface diffusions as well as activation of N acceptors during annealing induced such a low specific contact resistivity.
Co-reporter:Li Gong, Jianguo Lu, Zhizhen Ye
Solar Energy Materials and Solar Cells 2010 94(6) pp: 937-941
Publication Date(Web):
DOI:10.1016/j.solmat.2010.02.026
Co-reporter:Zao Yang, Zhizhen Ye, Binghui Zhao, Xiaolin Zong, Ping Wang
Physica E: Low-dimensional Systems and Nanostructures 2010 Volume 42(Issue 6) pp:1830-1833
Publication Date(Web):April 2010
DOI:10.1016/j.physe.2010.02.001
ZnO nanorods were synthesized by citric acid-assisted annealing route. In a phosphate buffer solution with a pH value of 7.4, glucose oxidase was immobilized on the surface of ZnO nanorod through chitosan-assisted cross-linking technique. The one-dimensional ZnO nanorods provide a large effective surface area with high surface-to-volume ratio and provide a favorable environment for the immobilization of GOx. The response time of this biosensor is less than 2 s. This biosensor has a very high sensitivity of 25.7 μA cm−2 mM−1. The low detection limit was estimated to be 0.01 mM. Two linear response ranges are 0.01–0.25 mM and 0.3–0.7 mM. The Michaelis–Menten constant is found to be 1.95 mM. These results demonstrate that zinc oxide nanorods have potential applications in biosensors.
Co-reporter:L. Gong, Z.Z. Ye, J.G. Lu
Vacuum 2010 Volume 85(Issue 3) pp:365-367
Publication Date(Web):24 September 2010
DOI:10.1016/j.vacuum.2010.07.009
In–N codoped p-type ZnMgO films have been prepared by direct current reactive magnetron sputtering. The effect of Mg content on the properties of In–N codoped ZnMgO films was examined. The Mg content in the film is directly proportional to that in the target suggesting the same sputtering mechanism of Zn and Mg. The p-type behaviour of ZnMgO films was deteriorated with the Mg content increasing. The bandgap engineering, due to the fact of Mg substituting Zn, was realized in p-type ZnMgO films.
Co-reporter:Li Gong, Zhizhen Ye, Jianguo Lu, Liping Zhu, Jingyun Huang, Xiuquan Gu, Binghui Zhao
Vacuum 2010 Volume 84(Issue 7) pp:947-952
Publication Date(Web):4 March 2010
DOI:10.1016/j.vacuum.2010.01.010
Al-doped ZnO (AZO) thin films have been prepared on glass substrates by pulsed laser deposition. The structural, optical, and electrical properties were strongly dependent on the growth temperatures. The lowest resistivity of 4.5 × 10−4 Ωcm was obtained at an optimized temperature of 350 °C. The AZO films deposited at 350 °C also had the high optical transmittance above 87% in the visible range and the low transmittance (<15% at 1500 nm) and high reflectance (∼50% at 2000 nm) in the near-IR region. The good IR-reflective properties of ZnO:Al films show that they are promising for near-IR reflecting mirrors and heat reflectors.
Co-reporter:Y. J. Zeng, Z. Z. Ye, F. Liu, D. Y. Li, Y. F. Lu, W. Jaeger, H. P. He, L. P. Zhu, J. Y. Huang and B. H. Zhao
Crystal Growth & Design 2009 Volume 9(Issue 1) pp:263
Publication Date(Web):November 19, 2008
DOI:10.1021/cg800422g
ZnO/MgO quasi core−shell quantum dots (QDs) were grown by a metal-organic chemical vapor deposition method on silicon substrates. The core−shell structure was well-characterized by a combination of cross-sectional transmission electron microscopy and angle-resolved X-ray photoelectron spectroscopy (XPS). Valence band XPS measurements were performed to investigate the effects of MgO shell layer on the energy band of ZnO/MgO QDs. Photoluminescence (PL) emission from the QDs showed remarkable enhancement after the growth of the MgO layer. In addition, exciton binding energy of 118 ± 5 meV in the ZnO/MgO QDs was obtained from temperature-dependent PL.
Co-reporter:G.D. Yuan, Z.Z. Ye, J.Y. Huang, L.P. Zhu
Solid State Communications 2009 Volume 149(7–8) pp:290-292
Publication Date(Web):February 2009
DOI:10.1016/j.ssc.2008.12.001
We report the fabrication of p-ZnO/n- Zn0.8Cd0.2O/n-ZnO heterojunctions that contain Al–N codoped p-ZnO, undoped n- Zn0.8Cd0.2O, and Al-doped n-ZnO layers. An InZn alloy is used as the p- and n-ZnO Ohmic contact electrodes. This structure exhibits improved rectifying p–n junction behavior, with forward turn-on voltage in the range of 3–5 V. The reverse breakdown voltage can be as high as 15 V, with 10−6-A reverse leakage current. Photoluminescence spectra show strong near band-edge emissions for both p- and n-ZnO at 368 nm and for undoped n- Zn0.8Cd0.2O, which is substantially red-shifted to 399 nm.
Co-reporter:Quan-Bao Ma, Zhi-Zhen Ye, Hai-Ping He, Li-Ping Zhu, Jing-Yun Huang, Yin-Zhu Zhang, Bing-Hui Zhao
Scripta Materialia 2008 Volume 58(Issue 1) pp:21-24
Publication Date(Web):January 2008
DOI:10.1016/j.scriptamat.2007.09.009
Highly transparent conductive and near-infrared (IR) reflective Ga-doped ZnO films were deposited on glass substrate by DC reactive magnetron sputtering. The influence of post-annealing temperature on the structural, electrical and optical properties of the films was investigated. The lowest resistivity of 2.6 × 10−4 Ω cm was obtained at an annealing temperature of 450 °C. The films have low transmittance and high reflectance in the near-IR range. The average transmittance of the films is over 90% in the visible range.
Co-reporter:Lingxiang Chen, Zhizhen Ye, Shisheng Lin, Haiping He, Yujia Zeng, Binghui Zhao, Liping Zhu
Materials Letters 2008 Volume 62(17–18) pp:2554-2556
Publication Date(Web):30 June 2008
DOI:10.1016/j.matlet.2007.12.046
Co-reporter:Quan-Bao Ma, Hai-Ping He, Zhi-Zhen Ye, Li-Ping Zhu, Jing-Yun Huang, Yin-Zhu Zhang, Bing-Hui Zhao
Journal of Solid State Chemistry 2008 Volume 181(Issue 3) pp:525-529
Publication Date(Web):March 2008
DOI:10.1016/j.jssc.2007.12.032
Highly transparent conductive and near infrared (IR) reflective Gallium-doped ZnMgO (Zn1−xMgxO:Ga) films with Mg content from 0 to 10 at% were deposited on glass substrate by DC reactive magnetron sputtering. X-ray diffraction shows all the ZnMgO:Ga films are polycrystalline and have wurtzite structure with a preferential c-axis orientation. Hall measurements indicate that the resistivity of these films obviously increases with the Mg concentration increasing. The average transmittance of Zn1−xMgxO:Ga films is over 90% in the visible range. All the Zn1−xMgxO:Ga films have low transmittance and high reflectance in the IR region.The figure shows transmittance and reflectance spectra of Zn1-xMgxO:Ga films measured in the wavelength range of 300–2500 nm. In the visible region the films are highly transparent, and their spectra are like those of dielectrics regardless of Mg content. In the IR region the films behave like metals and have high reflectance and low transmittance.
Co-reporter:Y.J. Zeng, Z.X. Jian, Z.Z. Ye, G.H. Gao, Y.F. Lu, B.H. Zhao, L.P. Zhu, S.H. Hu
Superlattices and Microstructures 2008 Volume 43(Issue 4) pp:278-284
Publication Date(Web):April 2008
DOI:10.1016/j.spmi.2007.12.002
Al–N codoped p-type ZnMgO thin films were prepared on three different substrates, namely glass, quartz, and silicon. Significant differences in the crystallinity, surface morphology, and electrical properties on these substrates were investigated by means of x-ray diffraction, field-emission scanning electron microscopy, and Hall-effect measurements. It is demonstrated that the Al donor enhances the incorporation of the N acceptor, resulting in better p-type conductivity. The incorporation of the N acceptor, as well as the Al and Mg, was confirmed x-ray photoelectron spectroscopy. Transmittance and photoluminescence spectra suggested a wider bandgap for the ZnMgO thin films in comparison with ZnO, which is believed to be the result of the incorporation of Mg.
Co-reporter:Y.Z. Zhang, H.P. He, Z.Z. Ye, H.H. Huang, J.G. Lu, M.X Qiu, B.H. Zhao, L.P. Zhu, J.Y. Huang
Materials Letters 2008 Volume 62(8–9) pp:1418-1420
Publication Date(Web):31 March 2008
DOI:10.1016/j.matlet.2007.08.074
p-type Li-doped ZnMgO thin films were prepared on glass substrates by pulsed laser deposition. The growth temperature varied from 400 to 650°C. All the films were highly c-axis oriented according to X-ray diffraction patterns. Hall-effect measurements indicated that the Li-doped ZnMgO film grown above 600°C failed in converting to p-type conduction. The film grown at 550°C showed the lowest resistivity of 10Ω cm with a hole concentration of 2.5 × 1018cm− 3. Temperature-dependent PL measurements revealed a dominant emission at 3.52eV up to RT, which may be assigned as exciton bound to neutral-acceptor (A0X) due to Li-doping. The Li acceptor activation energy in ZnMgO thin film was determined to be 135 ± 20meV.
Co-reporter:J.R. Wang, Z.Z. Ye, J.Y. Huang, Q.B. Ma, X.Q. Gu, H.P. He, L.P. Zhu, J.G. Lu
Materials Letters 2008 Volume 62(8–9) pp:1263-1266
Publication Date(Web):31 March 2008
DOI:10.1016/j.matlet.2007.08.024
ZnMgO nanorod arrays were synthesized by metal-organic chemical vapor deposition using diethylzinc and magnesium nitrate as the precursors. No additional oxidant gas source such as O2 or N2O was used. The ZnMgO nanorods were homogeneous in composition and uniform in diameter. The blueshift of near-band-edge PL emission could be readily identified as compared with undoped ZnO nanostructures, indicating the band-gap engineering in the ZnO nanoscale system. The growth process was investigated in detail by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The possible growth mechanism was proposed. It is believed that this growth process may facilitate the homogenous distribution of Mg in the ZnMgO nanorods.
Co-reporter:S.S. Lin, J.G. Lu, Z.Z. Ye, H.P. He, X.Q. Gu, L.X. Chen, J.Y. Huang, B.H. Zhao
Solid State Communications 2008 Volume 148(1–2) pp:25-28
Publication Date(Web):October 2008
DOI:10.1016/j.ssc.2008.07.028
The authors report growth of stable Na-doped p-type ZnO films through pulsed laser deposition. Magnetic field dependent Hall-effect measurements demonstrate the firm p-type conductivity of the Na-doped films. The Na related acceptor level was estimated to be ∼164 meV by temperature-dependent photoluminescence and low temperature photoluminescence excitation spectra. ZnO p–n homojunction light-emitting diode consisting of Al-doped n-type ZnO and Na-doped p-type ZnO was fabricated on Si substrates. The diode showed evident rectification behavior with threshold voltage of ∼3.3 eV. The electroluminescence from the diode was observed at 110 K, consisting of three emission bands of 2.24 eV, 2.52 eV, and 3.03 eV from the radiative recombinations in the p-type layer. This work firmly demonstrates that Na could be a good dopant to create stable p-type ZnO.
Co-reporter:Xinhua Pan, Zhizhen Ye, Jiesheng Li, Yujia Zeng, Xiuquan Gu, Liping Zhu, Binghui Zhao, Yong Che
Applied Surface Science 2007 Volume 253(Issue 14) pp:6060-6062
Publication Date(Web):15 May 2007
DOI:10.1016/j.apsusc.2007.01.003
Abstract
p-Type Zn0.9Mg0.1O thin films have been realized via monodoping of Li acceptor by using pulsed laser deposition. The Li-doped Zn0.9Mg0.1O thin films possessed a good crystallinity with a (0 0 0 2) preferential orientation and a high transmittance in the visible region. Secondary ion mass spectroscopy revealed that Li has been successfully incorporated into the Zn0.9Mg0.1O films. The obtained films with the best electrical properties show a hole concentration in the order of 1017 cm−3 and a room-temperature resistivity in the range of 58–72 Ω cm.
Co-reporter:Xinhua Pan, Zhizhen Ye, Jiesheng Li, Xiuquan Gu, Yujia Zeng, Haiping He, Liping Zhu, Yong Che
Applied Surface Science 2007 Volume 253(Issue 11) pp:5067-5069
Publication Date(Web):30 March 2007
DOI:10.1016/j.apsusc.2006.11.014
Abstract
p-Type ZnO thin films have been realized via monodoping antimony (Sb) acceptor by using pulsed laser deposition. The obtained films with the best electrical properties show a hole concentration in the order of 1018 cm−3 and resistivity in the range of 2–4 Ω cm. X-ray diffraction measurements revealed that all the films possessed a good crystallinity with (0 0 2)-preferred orientation. Guided by X-ray photoemission spectroscopy analysis and a model for large-sized-mismatched group-V dopant in ZnO, an SbZn–2VZn complex is believed to be the most possible acceptor in the Sb-doped p-type ZnO thin films.
Co-reporter:Y.J. Zeng, Z.Z. Ye, Y.F. Lu, J.G. Lu, W.Z. Xu, L.P. Zhu, B.H. Zhao, Y. Che
Chemical Physics Letters 2007 Volume 441(1–3) pp:115-118
Publication Date(Web):13 June 2007
DOI:10.1016/j.cplett.2007.04.089
The authors report on comparative study on ultraviolet (UV) photoconductivity of p-type ZnO:N films and n-type ZnO epilayer. As compared with the ZnO epilayer, the ZnO:N films show much higher photoconductivity but with faster decay. Surface adsorption of C and O, as identified by X-ray photoelectron spectroscopy, is believed to be a major contribution to the UV photoconductivity. The surface adsorption and photodesorption process, combined with a competition between holes and electrons, in p-type ZnO:N, is proposed tentatively, providing qualitative agreement with the observed behaviors.Comparative ultraviolet photoconductivity of p-type ZnO:N films and n-type ZnO epilayer.
Co-reporter:Y.-F. Lu;Z.-Z. Ye;Y.-J. Zeng;H.-P. He;L.-P. Zhu;B.-H. Zhao
Chemical Vapor Deposition 2007 Volume 13(Issue 6-7) pp:
Publication Date(Web):10 JUL 2007
DOI:10.1002/cvde.200604246
N-doped p-type ZnO films are grown on glass substrates by plasma-assisted metal–organic CVD at a low temperature of 250 °C. Scanning electron microscopy, X-ray diffraction, and Raman scattering spectroscopy are carried out to investigate the crystalline properties of the ZnO films. Results show a high degree of (0002) orientation and a little tensile stress in the films. Hall analyses show homogeneous p-type conduction. Room-temperature photoluminescence spectra display strong ultraviolet emission with a clear acceptor fingerprint.
Co-reporter:Y.J. Zeng, Z.Z. Ye, W.Z. Xu, B. Liu, Y. Che, L.P. Zhu, B.H. Zhao
Materials Letters 2007 Volume 61(Issue 1) pp:41-44
Publication Date(Web):January 2007
DOI:10.1016/j.matlet.2006.04.001
N-doped, p-type ZnO thin films have been grown by plasma-assisted metal-organic chemical vapor deposition method. The results under optimized growth conditions included a resistivity of 1.72 Ω cm, a Hall mobility of 1.59 cm2/V s, and a hole concentration of 2.29 × 1018 cm− 3, and were consistently reproducible. A N-related free-to-neutral-acceptor emission and an associated phonon replica were evident in room temperature photoluminescence spectra, from which the N acceptor energy level in ZnO was estimated to be 180 meV above the valence band maximum.
Co-reporter:Yangfan Lu, Zhizhen Ye, Yujia Zeng, Weizhong Xu, Liping Zhu, Binghui Zhao
Optical Materials 2007 Volume 29(Issue 12) pp:1612-1615
Publication Date(Web):August 2007
DOI:10.1016/j.optmat.2006.08.004
High quality N-doped ZnO films were grown at different RF powers on glass substrates by plasma-assisted metalorganic chemical vapor deposition. Scanning electron microscopy, X-ray diffraction and Hall analyses were carried out to investigate the effects of RF power variation on surface morphology, crystallinity and electrical properties of the ZnO films. Increasing the RF power resulted in compacter surface morphology and change of the crystallinity as well as incorporation of more N atoms. Films grown at 150 W exhibited the best p-type electrical properties. Moreover, room temperature photoluminescence spectra showed strong emission related to N acceptor.
Co-reporter:Haiping Tang, Liping Zhu, Zhizhen Ye, Haiping He, Yang Zhang, Mingjia Zhi, Fan Yang, Zhixiang Yang, Binghui Zhao
Materials Letters 2007 Volume 61(4–5) pp:1170-1173
Publication Date(Web):February 2007
DOI:10.1016/j.matlet.2006.06.085
Co-reporter:L.L. Chen, Z.Z. Ye, J.G. Lu, H.P. He, B.H. Zhao, L.P. Zhu, Paul K. Chu, L. Shao
Chemical Physics Letters 2006 Volume 432(1–3) pp:352-355
Publication Date(Web):4 December 2006
DOI:10.1016/j.cplett.2006.10.047
The influence of indium concentrations on electrical properties of In–N co-doped ZnO thin films has been studied. Based on Hall-effect measurements and analyses, impurity scattering is the dominant mechanism determining the diminished mobility in ZnO with higher In concentration. X-ray photoelectron spectroscopy reveals that the presence of In enhances the solubility of N with the formation of In–N and Zn–N bonds. The optimal properties, namely resistivity of 16.1 Ω cm and Hall mobility of 1.13 cm2 V−1 s−1, are obtained at an indium concentration of 0.14 at.%. The diffraction angle of co-doped ZnO is closest to that of un-doped ZnO.Dependence of electrical properties of In–N co-doped ZnO films on In concentrations.
Co-reporter:L.M. Yang, Z.Z. Ye, Y.J. Zeng, W.Z. Xu, L.P. Zhu, B.H. Zhao
Solid State Communications 2006 Volume 138(Issue 12) pp:577-579
Publication Date(Web):June 2006
DOI:10.1016/j.ssc.2006.04.029
High quality self-assemble ZnO quantum dots (QDs) have been successfully grown on the Si(111) substrates by metalorganic chemical vapor deposition (MOCVD). The diameter of ZnO QDs is about 10 nm in average, and the densities and the sizes of ZnO QDs can be well controlled by adjusting the growth temperature, which were evident in the SEM images. The properties and stress involved in ZnO QDs are studied by X-ray diffraction. In addition, room temperature photoluminescence spectra reveal that the ZnO QDs exhibit a band gap blue shift because of the quantum confinement effects.
Co-reporter:Quan-Bao Ma, Zhi-Zhen Ye, Hai-Ping He, Li-Ping Zhu, Jing-Yun Huang, Yin-Zhu Zhang, Bing-Hui Zhao
Scripta Materialia (January 2008) Volume 58(Issue 1) pp:21-24
Publication Date(Web):1 January 2008
DOI:10.1016/j.scriptamat.2007.09.009
Highly transparent conductive and near-infrared (IR) reflective Ga-doped ZnO films were deposited on glass substrate by DC reactive magnetron sputtering. The influence of post-annealing temperature on the structural, electrical and optical properties of the films was investigated. The lowest resistivity of 2.6 × 10−4 Ω cm was obtained at an annealing temperature of 450 °C. The films have low transmittance and high reflectance in the near-IR range. The average transmittance of the films is over 90% in the visible range.
Co-reporter:G.D. Yuan, Z.Z. Ye, J.Y. Huang, L.P. Zhu
Solid State Communications (February 2009) Volume 149(7–8) pp:290-292
Publication Date(Web):1 February 2009
DOI:10.1016/j.ssc.2008.12.001
We report the fabrication of p-ZnO/n- Zn0.8Cd0.2O/n-ZnO heterojunctions that contain Al–N codoped p-ZnO, undoped n- Zn0.8Cd0.2O, and Al-doped n-ZnO layers. An InZn alloy is used as the p- and n-ZnO Ohmic contact electrodes. This structure exhibits improved rectifying p–n junction behavior, with forward turn-on voltage in the range of 3–5 V. The reverse breakdown voltage can be as high as 15 V, with 10−6-A reverse leakage current. Photoluminescence spectra show strong near band-edge emissions for both p- and n-ZnO at 368 nm and for undoped n- Zn0.8Cd0.2O, which is substantially red-shifted to 399 nm.
Co-reporter:Mu Xiao, Yaguang Li, Yangfan Lu and Zhizhen Ye
Journal of Materials Chemistry A 2015 - vol. 3(Issue 6) pp:NaN2706-2706
Publication Date(Web):2014/12/03
DOI:10.1039/C4TA05931J
In this paper, the ZrO2:Fe nanostructures with precisely controlled Fe doping contents are obtained by using a template method. The characterizations obviously show that the as-prepared samples have hollow sphere-like morphology and high crystalline quality. Furthermore, the band gap of the ZrO2:Fe nanostructures is facilely tunable by controlling the Fe content. In addition, the density-functional theory (DFT) calculation reveals that the formation of an impurity band in the band gap narrows the band gap of the Fe-doped ZrO2 nanostructures. The visible-light driven photocatalytic activity of ZrO2 nanostructures could be remarkably enhanced by doping the Fe impurity. This can be attributed to the red shift of the absorption edge and the trapping effect of the ZrO2:Fe nanostructures. The research results provide a general and effective method to synthesize different photocatalysts with enhanced visible-light driven H2 evolution activity.
Co-reporter:Haiping He, Yanjie Wang, Jingrui Wang and Zhizhen Ye
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 33) pp:NaN14905-14905
Publication Date(Web):2011/07/11
DOI:10.1039/C1CP21527B
Negative thermal quenching of both the excitonic and green emissions is observed in ZnO nanosheets, from which the energy level of surface traps can be extracted based on a model of multi-level transitions. The present study demonstrates a non-destructive and easy method to determine the trap levels in semiconductor nanostructures.
Co-reporter:Minggang Zhao, Jingyun Huang, Yu Zhou, Xinhua Pan, Haiping He, Zhizhen Ye and Xiaoqing Pan
Chemical Communications 2013 - vol. 49(Issue 69) pp:NaN7658-7658
Publication Date(Web):2013/07/01
DOI:10.1039/C3CC43154A
Controlled synthesis of spinel ZnFe2O4 nanoparticle-decorated ZnO nanofiber heterostructures was carried out with regularly varied particle sizes and uniform distribution. The obtained heterostructures possessed enhanced intrinsic peroxidase-like activity, and the activities regularly changed as the sizes of ZnFe2O4 nanoparticles varied. The heterostructures were further applied in sensitive colorimetric biosensing of urine glucose.
Co-reporter:Xiaoyong Liang, Sai Bai, Xin Wang, Xingliang Dai, Feng Gao, Baoquan Sun, Zhijun Ning, Zhizhen Ye and Yizheng Jin
Chemical Society Reviews 2017 - vol. 46(Issue 6) pp:NaN1759-1759
Publication Date(Web):2017/02/28
DOI:10.1039/C6CS00122J
Colloidal metal oxide nanocrystals offer a unique combination of excellent low-temperature solution processability, rich and tuneable optoelectronic properties and intrinsic stability, which makes them an ideal class of materials as charge transporting layers in solution-processed light-emitting diodes and solar cells. Developing new material chemistry and custom-tailoring processing and properties of charge transporting layers based on oxide nanocrystals hold the key to boosting the efficiency and lifetime of all-solution-processed light-emitting diodes and solar cells, and thereby realizing an unprecedented generation of high-performance, low-cost, large-area and flexible optoelectronic devices. This review aims to bridge two research fields, chemistry of colloidal oxide nanocrystals and interfacial engineering of optoelectronic devices, focusing on the relationship between chemistry of colloidal oxide nanocrystals, processing and properties of charge transporting layers and device performance. Synthetic chemistry of colloidal oxide nanocrystals, ligand chemistry that may be applied to colloidal oxide nanocrystals and chemistry associated with post-deposition treatments are discussed to highlight the ability of optimizing processing and optoelectronic properties of charge transporting layers. Selected examples of solution-processed solar cells and light-emitting diodes with oxide-nanocrystal charge transporting layers are examined. The emphasis is placed on the correlation between the properties of oxide-nanocrystal charge transporting layers and device performance. Finally, three major challenges that need to be addressed in the future are outlined. We anticipate that this review will spur new material design and simulate new chemistry for colloidal oxide nanocrystals, leading to charge transporting layers and solution-processed optoelectronic devices beyond the state-of-the-art.
Co-reporter:Wen Dai, Xinhua Pan, Shanshan Chen, Cong Chen, Zhen Wen, Honghai Zhang and Zhizhen Ye
Journal of Materials Chemistry A 2014 - vol. 2(Issue 23) pp:NaN4614-4614
Publication Date(Web):2014/03/19
DOI:10.1039/C4TC00157E
Honeycomb-like NiO/ZnO heterostructured nanorods (NRs) were fabricated by a simple photochemical deposition method. The morphology of the NiO nanostructures can be rationally tailored by changing the concentration of the solution, reaction time and annealing temperature. A reasonable formation mechanism of the honeycomb-like NiO/ZnO NRs is proposed, which is closely related to the production of OH− in the vicinity of ZnO NRs during the photochemical deposition process. The fabricated NiO/ZnO p–n heterojunction shows a well-defined rectifying characteristic with a turn-on voltage of 0.66 V and a negligible leakage current. Moreover, the UV detection performance increases considerably compared to that of bare ZnO NRs, which is attributed to the change of nanostructure and the extended carrier depletion region near p-NiO/n-ZnO junctions.
Co-reporter:H. H. Zhang, X. H. Pan, B. Lu, J. Y. Huang, P. Ding, W. Chen, H. P. He, J. G. Lu, S. S. Chen and Z. Z. Ye
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 27) pp:NaN11235-11235
Publication Date(Web):2013/05/22
DOI:10.1039/C3CP51156A
The valence band offsets (ΔEV) of Zn1−xMgxO/ZnO heterojunctions grown by plasma-assisted molecular beam epitaxy were measured by photoelectron spectroscopy. From the directly obtained ΔEV values, the related conduction band offsets (ΔEC) were deduced. All the Zn1−xMgxO/ZnO heterojunctions exhibit a type-I band alignment with the ΔEC/ΔEV estimated to be 1.5, 1.8, 2.0 for x = 0.10, 0.15 and 0.20, respectively. The band offsets of Zn1−xMgxO/ZnO heterojunctions depend on Mg composition. The accurate determination of energy band alignment of Zn1−xMgxO/ZnO is helpful for designing ZnO based optoelectronic devices.
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