Investigation of basic optical characteristics in Te-Ge binary thin films for the optical memory

In this work, we have studied the variation of optical characteristics in Te_100-xGe, binary system thin films with compositional ranges of x=10 to x=60. To obtain the optimum composition capable of utilizing as an optical recording material, the transmittance and reflectance changes and the contrast ratio between amorphous and crystalline films are investigated using a diode laser with wavelength of 780 nm. It was found that the as-deposited amorphous thin films prepared by thermal evaporation are crystallized by annealing around the crystalline temperature T_c for each film and then crystalline phases are analyzed using XRD. The reflectance of crystalline films increased the comparison with the amorphous films. The contrast ratio showed 1.45~2.1. The amorphous thin films expect with composition of x=50, 60 at% and the crystalline thin films with composition 7=10, 40 at% showed the transmittance change in 80%RH/66°C environments. As the results, the Te₅₀Ge₅₀, Te₄₀Ge₆₀ thin film can be estimated at the optimum media for optical recording in our study