Evolution of crystallinity in mixed-phase (a+mu c)-Si : H as determined by real time spectroscopic ellipsometry

The ability to characterize the phase of the intrinsic (i) layers incorporated into amorphous silicon [a-Si:H] and microcrystalline silicon [muc-Si:H] thin film solar cells is critically important for cell optimization. In our research, a new method has been developed to extract the thickness evolution of the muc-Si:H volume fraction in mixed phase amorphous + microcrystalline silicon [(a+muc)-Si:H] i-layers. Ibis method is based on real time spectroscopic ellipsometry measurements performed during plasma-enhanced chemical vapor deposition of the films. In the analysis, the thickness at which crystallites first nucleate from the a-Si:H phase can be estimated, as well as the nucleation density and microcrystallite cone angle. The results correlate well with structural and solar cell measurements.