Abstract
Amorphous silicon plays a crucial role in renewable energy and energy storage devices. Here, we report on the application of the Kramers–Kronig consistent B-spline parametric model to the complex dielectric function of non-hydrogenated amorphous silicon (a-Si). a-Si thin films were deposited onto quartz and thermal \(\hbox {SiO}_2\) /c-Si(100) substrates using radio-frequency magnetron sputtering at a relatively low temperature of 195 K (−78 °C). Room-temperature ex situ spectroscopic ellipsometry was employed post-growth with high resolution, and the energy-slicing B-spline parametric model was implemented within a multilayered structure using 14 non-vanishing optimized B-spline series expansion coefficients, \(\{c_i\}\) , which resulted in accurate determination of the complex dielectric function, optical bandgap, and film thickness simultaneously. The correlation matrix of the fitting parameters was further obtained and analyzed in detail. The obtained B-spline parameterization represents an accurate basis reference for a-Si over the wide ultraviolet–visible–near-infrared (UV–Vis-NIR) spectral range of 270–1240 nm corresponding to 1.0–4.6 eV. It was successfully applied to two amorphous silicon-based semiconductors until accurate fittings were achieved, which are the non-hydrogenated phase a-Si deposited under different growth conditions and the hydrogenated phase a- \(\hbox {Si}_x \hbox {H}_{1-x}\) with various atomic percentages of alloyed hydrogen.
Graphic Abstract
