Growth of Cu2ZnSnSe4 thin films by pulsed laser deposition and characterization of the obtained films

• Main Authors: Hung-ChiWei, 魏鴻企
• Other Authors: Xiao-ding Qi
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/82477952904963062951

碩士 === 國立成功大學 === 材料科學及工程學系 === 102 === Cu2ZnSnSe4 (CZTSe) targets were synthesized from pure elements by the solid-state reaction method. The targets were used for the deposition of CZTSe thin films using pulsed laser deposition (PLD) technique. Two growth processes were attempted. One was to deposit the films at room temperature (RT), which were then subjected to a post-deposition annealing at high temperatures. The other process was to grow the films of the desired phase directly on heated substrates (HS). During the RT deposition the target-to-substrate distance (TTSD), pulse frequency and laser fluence were varied. The grown films were characterized by a range of techniques, including grazing incident X-ray diffraction (GIXRD), energy dispersive X-ray spectroscopy, and scanning electron microscopy. The influences of above growth parameters as well as the annealing temperature on the composition, phase and microstructure of the films were studied. Some of the optimized parameters were then adopted in the HS growth. In addition to the compositional and structural analyses, the electrical and optical properties of the HS films were also studied by the Hall-effect and optical absorption measurements. The effects of substrate temperature and chamber vacuum on the HS film properties were discussed. The results showed that CZTSe targets of a pure phase could be obtained by sintering at 300 oC for 12 hr. In terms of the film growth, it was found that TTSD affected both the phase and thickness of the films, while laser frequency only changed film thickness. Varying laser fluence or chamber vacuum had the effect to change Cu content in the deposited films. Substrate temperature determined the crystallinity of the films. A suitable temperature could also prevent the films from the strain-induced peeling off. The optimal growth parameters were summarized as follows: TTSD 6 cm, vacuum 10-3 Torr, pulse frequency 5 Hz, laser fluence 1.1 J/cm2, and substrate temperature 300 oC. Under such a condition, films of a pure phase were obtained, which showed sharp GIXRD peaks with a preferred (112) orientation. They had a bandgap of 1.34 eV and P-type carrier concentration of 1.21x1020 cm-3.