Wei Guang Yang

Preparation and Characterization of ZnO Nanowire Arrays Grown on Different ZnO Seed Layers by Hydrothermal Method

Due to its suitable band gap, low cost, environmental friendliness, and high electron mobility, ZnO, naturally n-type semiconductor with a wide bandgap (Eg = 3.37 eV), is widely studied, as a window layer of heterojunction solar cells. In this study, the ZnO nanowire arrays were grown on the different ZnO seed layers by hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Vis spectra were used to characterize the ZnO nanowire arrays. The results indicate the seed layer can effect the size distribution, density, crystal structure and optical properties of the nanowire arrays.

Ni-Induced Lateral Fast Crystallization of Amorphous Silicon Film by Microwave Annealing

Polycrystalline Si (poly-Si) thin films for application to display devices and solar cell are generally fabricated by crystallizing amorphous Si (a-Si) thin film precursors. In this paper, studies on Ni-induced lateral crystallization of a-Si thin films by microwave annealing at low temperature were reported. The crystallization of a-Si thin films was enhanced by applying microwaves to the films. The poly-Si films were invested by Optical Microscopy, X-ray Diffraction (XRD) , Raman Spectroscopy and Scanning Electron Microscope(SEM). After processing of Ni-induced lateral crystallization by microwave annealing above 500°C, the a-Si has begun to be crystallized with large grains having the main (111) orientation. The rate of crystallization at 550°C is about 0.033μm/min. Compared to Ni-induced lateral crystallization by conventional furnace annealing, Ni-induced lateral crystallization by microwave annealing both lowers the crystallization temperature and reduces the time of crystallization. The crystallization mechanism during microwave annealing was also studied. The technique that combines Ni-induced lateral crystallization with microwave annealing has potential applications in thin-film transistors (TFT’s) and solar cell.

Preparation and Properties of ZnO@ZnS Nano-Array Core-Shell Structure with Different Concentration of TAA

ZnO@ZnS nano-array core-shell structure was synthesized through a solution method using a thioacetamide (TAA) solution in deionized water. The as-synthesized ZnO nano-array and TAA solution were employed to supply zinc and sulfur ions to form the ZnO@ZnS core-shell structures. The properties of the structure were characterized by X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM) and UV-Vis spectra. The results indicate that ZnO nano-array was coated with ZnS particles. The concentration of TAA solution can affect the diameter, surface roughness and optical properties of the ZnO@ZnS nano-array core-shell structures.

Properties of Ohmic Contact of Au Electrode on Polycrystalline Mercuric Iodide

Polycrystalline mercuric iodide films are being developed as a new detector technology for digital X-ray imaging. The properties of the contact between electrode and film play an important role in the performance of the polycrystalline mercuric iodide detector. In this paper, the films were grown on the thin film transistor (TFT) substrates via hot-wall physical vapor deposition method. Au front contacts were deposited onto the HgI2 films by thermal evaporation under a vacuum of 10-4Pa. The HgI2 films were characterized by X-ray diffraction (XRD). The surface morphology of the films before and after the process of evaporating Au was compared by scan electron microscopes (SEM). And the I-V curve was measured after evaporating Au electrode. The results indicate that the polycrystalline mercuric iodide films we prepared have a very strong (001) growth-preference. Au was deposited on the grain surface forming excellent ohmic contact with polycrystalline α-HgI2 film which was also confirmed by the I-V characteristic of HgI2 film after the process of evaporating Au electrode.

Preparation and Properties of Cu2ZnSnS4 Nanoparticles by Solvothermal Method

Earth-abundant Cu2ZnSnS4(CZTS), a promising alternative photovoltaic material, was prepare by a mild solvothermal route and annealed. The as-prepared nanoparticles were obtained at 200°C and analyzed by X-ray diffraction(XRD). The crystallinity of CZTS particles was greatly improved by annealing in N2 gas shown in XRD. EDS results indicate the composition of the film and the variety of the ratio of the metal atoms and S atoms.

Study and Preparation of Pure-Phase Cu2ZnSnS4 Nanocrystals by Solvothermal Method

The as-prepared high-quality Cu2ZnSnS4 nanocrystals were prepared by solvothermal method. The influence of the reaction temperature, growth time and mixed solvent on the structural and composition of the Cu2ZnSnS4 nanocrystals was investigated. XRD result shows the percentage of ethylenediamine in the mixed solvent have an important influence in the synthesis process of pure-phase Cu2ZnSnS4 nanocrystals. EDS result proves the particles belong to Cu rich and Zn poor composition.

Electrical Properties of Polycrystalline α-HgI2 Detector

Potentially low cost and large-area polycrystalline mercuric iodide (α-HgI2) is one of the preferred materials for the fabrication of room temperature X-ray and gamma-ray detectors. In this paper, polycrystalline α-HgI2 films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. X-ray diffraction (XRD), scan electron microscopes (SEM) and Raman spectrum were used to characterization the HgI2 films obtained, and I-V characteristics was also tested. Using the polycrystalline α-HgI2 films, we get the detector. According to the detector, on the one hand, a dark current test is made by using KEITHL EY 485 picoammeter; on the other hand, the Agilent 4294A precision impedance analyzer is taken to test the characteristic curve of its capacitor frequency.

Growth Time Influence on Polycrystalline α-HgI2 Films

Polycrystalline α-HgI2 films have been grown on TFT substrates using hot-wall vapor phase deposition (HWPVD) with the different growth times. The influence of different growth times (1 hour, 2 hours, 3 hours, 4 hours) on the structural and electrical properties of the polycrystalline α-HgI2 films is investigated. Metallurgical microscope, scan electron microscopes (SEM) and X-ray diffraction (XRD) characterization and the electric transport properties were investigated by the I-V characteristics. The polycrystalline α-HgI2 films growth by 3 hours show more better performance than others. So we use it preparation a detector.Finally, capacitance frequency characteristics analysis showed the detector have good performance.

The Role of CdS Buffer Layer in ZnO Nanowire Arrays/SnS Thin Film Solar Cells

SnS is a promising p-type semiconductor material for low-cost and low-toxic solar cells due to its exciting properties, such as high absorption in the visible range, little toxicity, inexpensiveness, and so on. The CdS nano-layer used as buffer layer of ZnO nanowire arrays/CdS/SnS thin film solar cells was prepared by thermal evaporation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), UV-Vis spectra, Hall effect measurement system and I-V measurement system were used to characterize the ZnO nanowire arrays/CdS/SnS thin film solar cells. It is found that the CdS nano-layer plays a key role in reducing the leakage current.

Effect of Seed Layers Prepared by Vertical Deposition Method on the Growth and Properties of Oriented Polycrystalline α-HgI2 Films

Polycrystalline α-HgI2 films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. The influence of the α-HgI2 seed layers on the structural and electrical properties of the polycrystalline α-HgI2 films was investigated. It is found that the α-HgI2 seed layers play an important role in reducing the grain sizes, increasing the density improving the crystallographic orientation and electrical properties of the polycrystalline α-HgI2 films.