The optical reflectance and transmittance spectra in the wavelength range of 300-2500 nm are used to compute the absorption coefficient of zinc oxide films annealed at different post-annealing temperatures 400, 500 an...The optical reflectance and transmittance spectra in the wavelength range of 300-2500 nm are used to compute the absorption coefficient of zinc oxide films annealed at different post-annealing temperatures 400, 500 and 600°C.The values of the cross point between the curves of the real and imaginary parts of the optical conductivity ɑ_1 and ɑ_1 with energy axis of films exhibit values that correspond to optical gaps and are about 3.25-3.3 eV. The maxima of peaks in plots dR/dλ and dT/dλ versus wavelength of films exhibit optical gaps at about 3.12-3.25 eV.The values of the fundamental indirect band gap obtained from the Tauc model are at about 3.14-3.2 eV. It can be seen that films annealed at 600°C have the minimum indirect optical band gap at about 3.15 eV. The films annealed at 600°C have Urbach＇s energy minimum of 1.38 eV and hence have minimum disorder. The dispersion energy d of films annealed at 500°C has the minimum value of 43 eV.展开更多
Single crystalline Tm2O3 films were grown on Si （001） substrates by molecular beam epitaxy using metallic Tm source and atomic oxygen source. X-ray photoelectron spectroscopy, atomic force microscopy and high-resolu...Single crystalline Tm2O3 films were grown on Si （001） substrates by molecular beam epitaxy using metallic Tm source and atomic oxygen source. X-ray photoelectron spectroscopy, atomic force microscopy and high-resolution transmission electron microscopy were employed to investigate the compositions, surface morphology and microstructure of the sample. A very flat surface with a root mean square roughness of 0.3 nm could be reached, and a sharp interface between the film and the Si substrate was achieved. The result of optical spectrum at ultraviolet and visible wavelengths showed that the band gap of the Tm2O3 film was 5.76 eV.展开更多
Thin films of tin selenide（Sn_xSe_y） with an atomic ratio of r =[y/x]= 0.5,1 and 1.5 were prepared on a glass substrate at T = 470℃using a spray pyrolysis technique.The initial materials for the preparation of the ...Thin films of tin selenide（Sn_xSe_y） with an atomic ratio of r =[y/x]= 0.5,1 and 1.5 were prepared on a glass substrate at T = 470℃using a spray pyrolysis technique.The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride（SnCl_4·5H_2O） and selenide acide（H_2SeO_3）.The prepared thin films were characterized by X-ray diffraction（XRD）,scanning electron microscopy,scanning tunneling microscopy,scanning helium ion microscopy,and UV-vis spectroscopy.The photoconductivity and thermoelectric effects of the Sn_xSe_ythin films were then studied.The Sn_xSe_y thin films had a polycrystalline structure with an almost uniform surface and cluster type growth.The increasing atomic ratio of r in the films,the optical gap,photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV,0.01 to 0.31 and -26.2 to—42.7 mV/K （at T = 350 K）,respectively.In addition,the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe_2 phases.展开更多
文摘The optical reflectance and transmittance spectra in the wavelength range of 300-2500 nm are used to compute the absorption coefficient of zinc oxide films annealed at different post-annealing temperatures 400, 500 and 600°C.The values of the cross point between the curves of the real and imaginary parts of the optical conductivity ɑ_1 and ɑ_1 with energy axis of films exhibit values that correspond to optical gaps and are about 3.25-3.3 eV. The maxima of peaks in plots dR/dλ and dT/dλ versus wavelength of films exhibit optical gaps at about 3.12-3.25 eV.The values of the fundamental indirect band gap obtained from the Tauc model are at about 3.14-3.2 eV. It can be seen that films annealed at 600°C have the minimum indirect optical band gap at about 3.15 eV. The films annealed at 600°C have Urbach＇s energy minimum of 1.38 eV and hence have minimum disorder. The dispersion energy d of films annealed at 500°C has the minimum value of 43 eV.
基金Project supported by the National Natural Science Foundation of China (60806031, 11004130)the Natural Science Foundation of Zhejiang Province, China (Y6100596)
文摘Single crystalline Tm2O3 films were grown on Si （001） substrates by molecular beam epitaxy using metallic Tm source and atomic oxygen source. X-ray photoelectron spectroscopy, atomic force microscopy and high-resolution transmission electron microscopy were employed to investigate the compositions, surface morphology and microstructure of the sample. A very flat surface with a root mean square roughness of 0.3 nm could be reached, and a sharp interface between the film and the Si substrate was achieved. The result of optical spectrum at ultraviolet and visible wavelengths showed that the band gap of the Tm2O3 film was 5.76 eV.
文摘Thin films of tin selenide（Sn_xSe_y） with an atomic ratio of r =[y/x]= 0.5,1 and 1.5 were prepared on a glass substrate at T = 470℃using a spray pyrolysis technique.The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride（SnCl_4·5H_2O） and selenide acide（H_2SeO_3）.The prepared thin films were characterized by X-ray diffraction（XRD）,scanning electron microscopy,scanning tunneling microscopy,scanning helium ion microscopy,and UV-vis spectroscopy.The photoconductivity and thermoelectric effects of the Sn_xSe_ythin films were then studied.The Sn_xSe_y thin films had a polycrystalline structure with an almost uniform surface and cluster type growth.The increasing atomic ratio of r in the films,the optical gap,photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV,0.01 to 0.31 and -26.2 to—42.7 mV/K （at T = 350 K）,respectively.In addition,the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe_2 phases.
