The optical properties of hexagonal boron nitride （h-BN） thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV-visible transmittance and reflection spectr...The optical properties of hexagonal boron nitride （h-BN） thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV-visible transmittance and reflection spectra, h-BN thin films with a wide optical band gap Eg （5.86 eV for the as-deposited film and 5.97 eV for the annealed film） approaching h-BN single crystal were successfully prepared by radio frequency （RF） bias magnetron sputtering and post-deposition annealing at 970 K. The optical absorption behaviour of h-BN films accords with the typical optical absorption characteristics of amorphous materials when fitting is made by the Urbach tail model. The annealed film shows satisfactory structure stability. However, high temperature still has a significant effect on the optical absorption properties, refractive index n, and optical conductivity σ of h-BN thin films. The blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures. In addition, it is found that the refractive index clearly exhibits different trends in the visible and ultraviolet regions. Previous calculational results of optical conductivity of h-BN films are confirmed in our experimental results.展开更多
Using CH4 and CF4 precursor gases, amorphous fluorinated hydrocarbon (a-C:F:H) films were prepared with the method of microwave electronic cyclotron resonant (ECR) plasma chemical vapor deposition. Deposition rate of ...Using CH4 and CF4 precursor gases, amorphous fluorinated hydrocarbon (a-C:F:H) films were prepared with the method of microwave electronic cyclotron resonant (ECR) plasma chemical vapor deposition. Deposition rate of the film firstly increases and then decreases with variable flow ratios R {[CF4]/([CF4] + [CH4]} due to the competition between deposition and etching process. Results from Fourier-transform infrared transmission spectroscopy of these films show that C-F bond configuration in a-C:F:H films evolves with the variable gas flow ratios R. The locations of the C-F peaks in IR spectra shift to higher frequency with the increase of R, and finally the structure in films with R >75% takes on a PTFE-like structure, which mainly consists of -CF2- chain. The change of optical band gap Eg deduced by a Tauc plot with R is also discussed.展开更多
Nanometer multilayer composite films of lead phthalocyanine(PbPc) and vanadyl phthalocyanine(VOPc) were prepared by vacuum vapor deposition. It is found that a new absorption peak around 940 nm appeared as discovered ...Nanometer multilayer composite films of lead phthalocyanine(PbPc) and vanadyl phthalocyanine(VOPc) were prepared by vacuum vapor deposition. It is found that a new absorption peak around 940 nm appeared as discovered by UV-visible absorption analysis. Compared to the Q bands absorption of single component films of VOPc and PbPc, the new peak is red-shifted. It is also found that the new peak shows a small red-shift when the thickness of the PbPc layer increases. It is concluded that the new peak is a result of composition, and the red-shift is caused by both interface effect and quantum confinement effect of the nanometer multilayered structure.展开更多
基金supported by the National Natural Science Foundation of China (Grants Nos 60876006 and 60376007)the Natural Science Foundation of Beijing (Grants No 4072007)
文摘The optical properties of hexagonal boron nitride （h-BN） thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV-visible transmittance and reflection spectra, h-BN thin films with a wide optical band gap Eg （5.86 eV for the as-deposited film and 5.97 eV for the annealed film） approaching h-BN single crystal were successfully prepared by radio frequency （RF） bias magnetron sputtering and post-deposition annealing at 970 K. The optical absorption behaviour of h-BN films accords with the typical optical absorption characteristics of amorphous materials when fitting is made by the Urbach tail model. The annealed film shows satisfactory structure stability. However, high temperature still has a significant effect on the optical absorption properties, refractive index n, and optical conductivity σ of h-BN thin films. The blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures. In addition, it is found that the refractive index clearly exhibits different trends in the visible and ultraviolet regions. Previous calculational results of optical conductivity of h-BN films are confirmed in our experimental results.
基金The project supported by the National Nature Science Foundation of China (No. 10305008)
文摘Using CH4 and CF4 precursor gases, amorphous fluorinated hydrocarbon (a-C:F:H) films were prepared with the method of microwave electronic cyclotron resonant (ECR) plasma chemical vapor deposition. Deposition rate of the film firstly increases and then decreases with variable flow ratios R {[CF4]/([CF4] + [CH4]} due to the competition between deposition and etching process. Results from Fourier-transform infrared transmission spectroscopy of these films show that C-F bond configuration in a-C:F:H films evolves with the variable gas flow ratios R. The locations of the C-F peaks in IR spectra shift to higher frequency with the increase of R, and finally the structure in films with R >75% takes on a PTFE-like structure, which mainly consists of -CF2- chain. The change of optical band gap Eg deduced by a Tauc plot with R is also discussed.
文摘Nanometer multilayer composite films of lead phthalocyanine(PbPc) and vanadyl phthalocyanine(VOPc) were prepared by vacuum vapor deposition. It is found that a new absorption peak around 940 nm appeared as discovered by UV-visible absorption analysis. Compared to the Q bands absorption of single component films of VOPc and PbPc, the new peak is red-shifted. It is also found that the new peak shows a small red-shift when the thickness of the PbPc layer increases. It is concluded that the new peak is a result of composition, and the red-shift is caused by both interface effect and quantum confinement effect of the nanometer multilayered structure.
