The metal-organic chemical vapor deposition （MOCVD） technique is a promising process for high-tem- perature superconductor YBa2Cu307_6（YBCO） preparation. In this technique, it is a challenge to obtain barium precu...The metal-organic chemical vapor deposition （MOCVD） technique is a promising process for high-tem- perature superconductor YBa2Cu307_6（YBCO） preparation. In this technique, it is a challenge to obtain barium precursors with high volatility. In addition, the purity, evaporation characteristics, and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film. In the present report, bis（2,2,6,6-tetramethyl- 3,5-heptanedionato）barium（II） （Ba（TMHD）2） was synthe- sized, and its structure was identified by PTIR, 1H NMR, 13C NMR, and ESI-MS spectroscopy. Subsequently, the thermal properties and the kinetics of decomposition were systemati- cally investigated by nonisothermal thermogravimetric anal- ysis methods. Based on the average apparent activation energy evaluated by the Ozawa, Kissinger, and Friedman methods, the volatilization process was discussed, and all results show that Ba（TMHD）2 is unstable and highly sensitive to the change of temperature during the whole evaporation process. There- fore, it is very important to choose suitable volatilization technology and conditions for avoiding Ba（TMHD）2 break- down （or thermal aging） during MOCVD process. Subse- quently, the possible conversion function is estimated through the Coats-Redfern method to characterize the evaporation patterns and follows a phase boundary reaction mechanism by the contracting surface equation with average activation energy of 118.7 kJ.mo1-1.展开更多
The influence of substrate temperature on microstructure, electrical and optical properties of in situ- textured zinc oxide （ZnO） films fabricated by metal organic chemical vapor deposition （MOVCD） had been invest...The influence of substrate temperature on microstructure, electrical and optical properties of in situ- textured zinc oxide （ZnO） films fabricated by metal organic chemical vapor deposition （MOVCD） had been investigated. Results indicated that the substrate tempera- ture played a very important role on preparation of ZnO thin film. With the raising of temperature, firstly ZnO crystals were perpendicular to the substrate, then they were grown inclining toward the substrate, finally ZnO crystals grown in layers but not regular. Consequently, ZnO film surface morphology changed from smooth to a pyramid structure and then disappeared little by little. Moreover, it was also found in this study that ZnO film was characterized with high crystallinity, low resistivity （2.17 x 10 2） and high transmittance （〉 80%）. These results suggested that ZnO thin film is suitable for front electrode of silicon thin film solar cell.展开更多
基金financially supported by the Major State Basic Research Development Program of China(No.2011CBA00105)the National Natural Science Foundation of China(Nos.51002149 and 21101151)
文摘The metal-organic chemical vapor deposition （MOCVD） technique is a promising process for high-tem- perature superconductor YBa2Cu307_6（YBCO） preparation. In this technique, it is a challenge to obtain barium precursors with high volatility. In addition, the purity, evaporation characteristics, and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film. In the present report, bis（2,2,6,6-tetramethyl- 3,5-heptanedionato）barium（II） （Ba（TMHD）2） was synthe- sized, and its structure was identified by PTIR, 1H NMR, 13C NMR, and ESI-MS spectroscopy. Subsequently, the thermal properties and the kinetics of decomposition were systemati- cally investigated by nonisothermal thermogravimetric anal- ysis methods. Based on the average apparent activation energy evaluated by the Ozawa, Kissinger, and Friedman methods, the volatilization process was discussed, and all results show that Ba（TMHD）2 is unstable and highly sensitive to the change of temperature during the whole evaporation process. There- fore, it is very important to choose suitable volatilization technology and conditions for avoiding Ba（TMHD）2 break- down （or thermal aging） during MOCVD process. Subse- quently, the possible conversion function is estimated through the Coats-Redfern method to characterize the evaporation patterns and follows a phase boundary reaction mechanism by the contracting surface equation with average activation energy of 118.7 kJ.mo1-1.
文摘The influence of substrate temperature on microstructure, electrical and optical properties of in situ- textured zinc oxide （ZnO） films fabricated by metal organic chemical vapor deposition （MOVCD） had been investigated. Results indicated that the substrate tempera- ture played a very important role on preparation of ZnO thin film. With the raising of temperature, firstly ZnO crystals were perpendicular to the substrate, then they were grown inclining toward the substrate, finally ZnO crystals grown in layers but not regular. Consequently, ZnO film surface morphology changed from smooth to a pyramid structure and then disappeared little by little. Moreover, it was also found in this study that ZnO film was characterized with high crystallinity, low resistivity （2.17 x 10 2） and high transmittance （〉 80%）. These results suggested that ZnO thin film is suitable for front electrode of silicon thin film solar cell.
