| Summary: | 碩士 === 國立交通大學 === 光電工程所 === 87 === We have successfully grown AgGaS2 thin films on quartz glass substrates by means of KrF excimer laser deposition from a mixture target of Ag2S and Ga2S3. We change substrate temperature from 430℃ to 570℃ and pulse repetation rate from 10 to 40 Hz. From X-ray diffraction and Raman scattering, all deposited films were chalcopyrite-type, polycrystalline AgGaS2 compound highly oriented in the (112) direction. The film grown at a substrate temperature 550℃, pulse repetition rate 20 Hz had the narrowest FWHM of XRD and density of Ag droplets on the deposited film surface was smallest from optical micro-scope and EMPA analysis. In addition, at substrate temperature 550℃ and pulse repetition rate 20-30 Hz, the A1 Raman mode indicates the deposited AgGaS2 films have better symmetry, narrower FWHM and larger intenisty. In PL spectrum measured at 17K, three emission peaks found at 2.156, 2.454 and 2.682 eV were deep-level, DAP transition and excition emission, respectively. Intensity of DAP transition emission become larger as well as the FWHM of emission peak was narrower (about 0.2 eV) while the quality of deposited AgGaS2 become better. The absorption edge of the deposited films was at about 2.64 eV at room temperature from measuements of UV-visible transmission.
At the final part of the exprement, we tried to improve quality of deposied films by means of introducing He as ambient gas during film growth. The FWHM of dirffaction peak in the (112) direction of deposited AgGaS2 film have reduced from 0.281°to 0.244°by introducing He to vacuum champer and the ratio of intensity of (112) dirffaction peak to intensity of Ag (111) dirffaction peak also increase by serval times. Furthermore, the intensity of A1-mode Raman spectra and the one of DAP transition emission also have increased. From the fact that we mentioned above, the quality of deposied films have improved by introducing He as ambient gas during film growth.
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