Nanosize crystalline silicon films are fabricated by using highly hydrogen-diluted silane as the reactive gas and activated with rf+dc double-power sources, in a conventional plasma-enhanced chemical-vapor-deposition system. The structure of the deposited films as studied by means of high-resolution electron microscopy, Raman scattering spectra, x-ray-diffraction pattern, IR transmission spectra, and ultraviolet ray analysis. The results show that there are many novel structural features and new physical properties for these nanosize crystalline silicon films. In particular, it is found that the optical-absorption coefficient α is higher than that of a-Si:H and μc-Si:H films, the room-temperature conductivity σd has the value of 10−3–10−1 Ω−1 cm−1, and the hydrogen content CH in nc-Si:H films is higher than 30 at. %. The nc-Si:H films have their peculiar features which are different from both a-Si:H and μc-Si:H films.
Raman spectra of (Mn, Co)-codoped ZnO films were investigated as functions of laser line and temperature. It is shown that the Raman shifts for different phonon modes exhibit redshift with temperature increasing, which can be attributed to the anharmonic effect in the material. Strong resonant Raman spectra of multi-LO phonons were observed as well for the films with the exciting photon energy higher than the direct band gap. Compared with the Raman spectra for ZnO films, the Mn, Co codoping effect on the spectra is revealed by the presence of additional phonon modes at 275 and 642cm−1 and another intensive phonon mode at around 524cm−1. With postannealing, Raman intensity of these phonon modes decrease, owing to the incorporation of oxygen into the films. Origins of the different phonon modes in the spectra are discussed as well.
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