RESUMO
The effect of radio frequency (RF) power on the variation in the nanostructures, chemical features and surface morphology of nc-Si:H thin films was investigated. SiH4 and H2 gases were used as source materials for the films. The films were prepared by plasma enhanced chemical vapor deposition (PECVD) techniques and the power ranged from 100 to 300 W. The average crystal size of the films varied from -1 to -12 nm and the highest crystalline volume fraction reached up to -33% when the applied RF power was 300 W. At the RF power of 300 W, the relative fraction of Si-H bond in the films (R(MONO) = Si-H/sigma[Si-H(n)]n = 1,2,3) was increased up to -29%. The variation in the nanostructures and surface features of the films with applied RF power can be interpreted by the change in the collision impact of the precursor on top of the growing films.
RESUMO
The nanostructural and optical features of Al-added nanocrystalline Si (nc-Si) thin films, which were prepared by co-sputtering Al-chips and a Si main target, were investigated in terms of Al-addition and post-deposition annealing conditions; the optical features like photoluminescence (PL) and electroluminescence (EL) were related with the variation in the nanostructure of the films. The PL intensity as well as the relative volume fraction of Si nanocrystallites increased with increasing the concentration of Al to a certain level. In particular, the PL spectra of the films which were prepared with 4 Al-chips and then annealed at 800 degrees C for 60 min exhibit a significant increase in intensity at a wavelength of approximately 620 nm, compared to those of the films prepared without Al-addition. It is highly likely that the observed increase in the PL intensity is caused by the raise in the total volume fraction of the approximately 3.0 nm-sized nanocrystallites in the films. It was found that the addition of Al as well as the post-deposition annealing can allow adjustment and control of the nanostructural and light-emission features of the nc-Si films.