Effect of deposition temperature on the structural properties of n+ μc-Si:H films

Abstract

The role of the deposition temperature (Td) on the structural properties of doped hydrogenated microcrystalline silicon (n+ μc-Si:H) has been studied through grazing incidence x-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy measurements. The deposition temperature was varied from 200 to 400 °C to observe the crystalline and amorphous phase formations in these films. The results show that the films deposited at low temperatures are more crystalline in nature than their high temperature counterparts. The elimination of the hydrogen atoms from the growing surface of the film seems to be correlated with the transition from the amorphous to the crystalline phase. This may be attributed to the following. At low deposition temperatures, the impinging H atoms from H2 dilution interact with a silicon-hydrogen bond on the grown surface, forming a volatile H2 molecule, to leave a Si–Si network. The result of this interaction may be responsible for the increased crystallinity. At high deposition temperatures, a transition between the hydrogen out-diffusion from Si–H bonds and the hydrogen incorporation by H2 dilution may lead to formation of Si–H bonds, again on the surface at a particular chemical equilibrium. This causes the film to remain amorphous.