INTERFERENCE-FREE DETERMINATION OF THE ABSORPTION-COEFFICIENT OF AMORPHOUS-SILICON THIN-FILMS

Hishikawa et al. [Jpn. J. Appl. Phys. 30 (1991) 1008] recently used transmission (T) and reflection (R) measurements on amorphous silicon films to show that interference-free absorption spectra (alpha) can be obtained by self-consistently solving T/(1-R). We show that if R is measured with the sample illuminated from the substrate-side T and R can be converted to T(f) and R(f), the transmission and reflection of a film on a semi-infinite substrate. For weakly absorbing films this simplifies the data analysis considerably as alpha can be obtained from T(f)/(1-R(f)) without any iterative procedures.