Micro-Raman and ultraviolet ellipsometry studies on μc-Si:H films prepared by H2 dilution to the Ar-assisted SiH4 plasma in radio frequency glow discharge

Abstract

Micro-Raman and ultraviolet ellipsometry studies have been performed on μc-Si:H films prepared by increasing the H2 dilution to the Ar-assisted SiH4 plasma in rf glow discharge. Combining the results obtained from the Bruggeman effective medium approximation fitting to the ellipsometry data and the Gaussian deconvolution of Raman spectra, it has been observed that the overall crystallinity improves along with the lowering in the incubation layer thickness, elimination of the amorphous component from the bulk, and the reduction of void fraction in the bulk as well as in the growth zone and surface layer. However, at very high H2/Ar ratio in the plasma a lowering in the crystallinity has been recorded along with an associated increase in the voids and an appearance of a small amorphous component in the bulk of the material. An increase in the voids arising at the grain boundary zone causes the hindrance to the crystallization in the network and is the result of higher H2 dilution, beyond a certain level, to the Ar-assisted SiH4 plasma, in the formation of a Si:H network. A correlation has been established between the data obtained from micro-Raman and ellipsometry in the structural characterization of a silicon–hydrogen system.