Spectral features of Co–Ge–Te amorphous thin film

Abstract

Optical spectral features of Co x Ge y Te 100− x− y amorphous thin films where 10≤ x≤35 and 41≤ y≤47 were studied for the first time. The transmittance and reflectance at normal incidence have been measured at room temperature in the spectral range 190–2500 nm. Refractive index and extinction coefficient have been evaluated in the above spectral range. Band tail width and energy gap were strongly affected by cobalt concentration in the “as prepared” amorphous thin film. Absorption band spectrum on the basis of the imaginary parts of the dielectric constant, ε 2, ε 1, refractive index, and extinction coefficient are also affected by cobalt content. On the other hand, the band edge parameter β remains almost constant.