Papers by Author: Ping Fan

Abstract: W-doped VO₂ films were prepared by DC reactive magnetron sputtering with various substrate bias. The microstructure, surface morphology, electrical and optical performances of the films were characterized by x-ray diffraction, scanning electron microscope, four-point probe method and spectrophotometer, respectively. The effect of substrate bias on microstructure, electrical and optical properties of sputtered W-doped VO₂ films was studied. The XRD results reveal that all samples exhibit preferential VO₂ (011) lattice orientation except the as-grown sample in our experiment. All the samples applied substrate bias show some degree optical switching performance in IR range, while the thermochromic phenomena was observed from resistance-temperature dependence plot only for the samples of substrate bias varied from-100V to-200V. This indicate that the optical and electrical properties of W-doped VO₂ films have different sensitivity to substrate bias. Optimal substrate bias of-200V sample shows fine semiconductor-metal-transition performance.

Abstract: Cu-doped CdS thin film has been successfully deposited by ion-beam sputtering deposition. The structural, morphology, optical and electrical properties of as-deposited and annealed Cu-doped CdS thin films were investigated. The heavily Cu-doped CdS films annealed at 400 °C was demonstrated to be improved in structural, morphology, electrical and optical properties. X-ray diffraction (XRD) analysis indicated the formation of polycrystalline CdS film with the structure of hexagonal wurtzite phase. No distinct impurity of Cu and Cu-S phase was detected in Cu-doped CdS thin films. Atomic force microscopy (AFM) revealed that the grain size was increased after annealed. Optical transmission and absorption spectroscopy measurement revealed a high absorption and energy band gap was of about 2.40 eV. The CdS thin film was of p-type conductivity and the resistivity was found to be 1.28×10^-1Ωcm.

Abstract: N-type Bi2Te3 and p-type Sb2Te3 thermoelectric thin films have been prepared by RF and DC co-sputtering. The Seebeck coefficient of n-type Bi2Te3 and p-type Sb2Te3 thin films is about -122 μVK-1 and 108 μVK-1, the power factor is about 0.82×10-3 Wm-1K-2 and 1.60×10-3 Wm-1K-2. Then, the films have been selected to fabricate the thin film thermoelectric generator. The results show that the open-circuit voltage of 12.2 mV and the output power of 3.32 μW are obtained for a thin film generator with the temperature difference at 60 K.

Abstract: Transparent conductive Cu-In-O thin films were deposited by reactive DC magnetron sputtering. Two types of targets were used. The first was In target covered with a fan-shaped Cu plate of the same radius and the second was Cu target on which six In grains of 1.5mm was placed with equal distance between each other. The samples were characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV/VIS spectrophotometer, four-probe measurement etc. SEM shows that the surfaces of all the samples are very smooth. EDX shows that the samples contain Cu, In as well as O, and different targets result in different atomic ratios of Cu to In. A diffraction peak related to rhombohedra-centered In₂O₃ (012) is observed in the XRD spectra of all the samples. For both the two targets, the transmittance decreases with the increase of O₂ flow rates. The direct optical band gap of all the samples is also estimated according to the transmittance curve. For both the two targets, different O₂ flow rates result in different sheet resistances and conductivities. The target of Cu on In shows more controllability in the composition and properties of Cu-In-O films.

Abstract: ZnO thin films were prepared by DC reactive magnetron sputtering at room temperature. Two of them were annealed with different modes under vacuum condition. One was annealed with constant temperature of 300°C ; the other was annealed with temperature rising step by step from room temperature to 300°C . By comparing the microstructure and optical properties of the as-grown and annealed samples, the effects of different annealing modes on ZnO films performances were revealed. The experiment results investigated that the sample annealed with constant temperature of 300°C has the high grain size and surface roughness. Both of the two annealing modes could release the intrinsic stresses to some degree. The optical band gap of the samples narrowed after annealing, and the two annealed samples have almost the same band gap. Strong green emissions are observed for all the samples, but the emission intensity decreased of the sample annealed with the temperature rising step by step compared with that of other samples.