Diamond films were prepared by hot-filament chemical vapour deposition system.Photothermal deflection technique has been used to measure thermal diffusivity of diamond films with substrates.The influence of silicon or...Diamond films were prepared by hot-filament chemical vapour deposition system.Photothermal deflection technique has been used to measure thermal diffusivity of diamond films with substrates.The influence of silicon or quartz substrate on the measurement of thermal diffusivity of film is presented.A simple two-layer model has been given to explain the effect of substrates on the measurement of thermal diffusivity and used to draw thermal diffusivity of diamond film from effective thermal diffusivity of film/substrate system.展开更多
Porous silicon samples have been successfully prepared by elect rochemical etching technique,which show intense photoluminescence(PL)in the visible wave-length region.The measurements of the temperature dependence of ...Porous silicon samples have been successfully prepared by elect rochemical etching technique,which show intense photoluminescence(PL)in the visible wave-length region.The measurements of the temperature dependence of PL in porous silicon show that the wavelength of the luminescent peak shifts to the blue and the PL band width does not change as the temperature of the sample increases over a wide range.The intensities of PL are measured as a function of temperature showing the confined exciton recombination behaviour,and the activation energies of 68.6 and 205meV of the excitons have been obtained for the low temperature and high temperature regions,respectively.The results suggest that the PL in porous silicon is due to the radiative recombination in a quantum wire system.展开更多
We have fabricated M doped (M = Al, Co, Fe, Ga, Ni and Zn) PrBa2Cu3O7 (PBCO), i.e. PrBa2(Cu1-xMx)3O7. The doping levels x are 0.05, 0.10, 0.15, and 0.20. X-ray data indicated no significant second phase for substituti...We have fabricated M doped (M = Al, Co, Fe, Ga, Ni and Zn) PrBa2Cu3O7 (PBCO), i.e. PrBa2(Cu1-xMx)3O7. The doping levels x are 0.05, 0.10, 0.15, and 0.20. X-ray data indicated no significant second phase for substituting Cu by Al, Co, Fe and Ga up to 20%. However impurity phases were detected for Ni and Zn substituted samples with doping levels equal to and higher than 15%. At 77 K the electrical resistivity of these compounds is orders in magnitude higher than that of PBCO. We also found that although the lattice parameters in the doped samples differ from PBCO, all samples remain orthorhombic. The lattice parameters of the doped sample are very close to those of YBa2Cu3O7-δ (YBCO) and PBCO. For this reason these compounds are better materials to be used as the I-layer for YBCO SIS junctions. Results of structural and transport studies on 2000 thick PrBa2[Cu0.80G0.2]3O7 (PBCGO) and YBCO/PBCGO multilayers are presented in this paper.展开更多
基金Supported by the National Advanced Materials Committee of China Under the Number of 863-715-03-04-01,and the Doctoral Research Foundation of the National Education Ministry of China.
文摘Diamond films were prepared by hot-filament chemical vapour deposition system.Photothermal deflection technique has been used to measure thermal diffusivity of diamond films with substrates.The influence of silicon or quartz substrate on the measurement of thermal diffusivity of film is presented.A simple two-layer model has been given to explain the effect of substrates on the measurement of thermal diffusivity and used to draw thermal diffusivity of diamond film from effective thermal diffusivity of film/substrate system.
文摘Porous silicon samples have been successfully prepared by elect rochemical etching technique,which show intense photoluminescence(PL)in the visible wave-length region.The measurements of the temperature dependence of PL in porous silicon show that the wavelength of the luminescent peak shifts to the blue and the PL band width does not change as the temperature of the sample increases over a wide range.The intensities of PL are measured as a function of temperature showing the confined exciton recombination behaviour,and the activation energies of 68.6 and 205meV of the excitons have been obtained for the low temperature and high temperature regions,respectively.The results suggest that the PL in porous silicon is due to the radiative recombination in a quantum wire system.
文摘We have fabricated M doped (M = Al, Co, Fe, Ga, Ni and Zn) PrBa2Cu3O7 (PBCO), i.e. PrBa2(Cu1-xMx)3O7. The doping levels x are 0.05, 0.10, 0.15, and 0.20. X-ray data indicated no significant second phase for substituting Cu by Al, Co, Fe and Ga up to 20%. However impurity phases were detected for Ni and Zn substituted samples with doping levels equal to and higher than 15%. At 77 K the electrical resistivity of these compounds is orders in magnitude higher than that of PBCO. We also found that although the lattice parameters in the doped samples differ from PBCO, all samples remain orthorhombic. The lattice parameters of the doped sample are very close to those of YBa2Cu3O7-δ (YBCO) and PBCO. For this reason these compounds are better materials to be used as the I-layer for YBCO SIS junctions. Results of structural and transport studies on 2000 thick PrBa2[Cu0.80G0.2]3O7 (PBCGO) and YBCO/PBCGO multilayers are presented in this paper.
