Stability of Te–Cu amorphous alloy thin films for optical recording

We have studied the structure and optical stability of Te–Cu thin film alloy candidates for write‐once optical recording. Films prepared by rf diode sputtering with 20–50 at. % Cu are amorphous, as‐sputtered. One of these, Te65 Cu35 , has a relatively high crystallization temperature (150 °C), as determined by x‐ray diffraction. Near the eutectic composition (∼29 at .% Cu), alloy films have stable optical properties after accelerated aging at 60 °C and 85% relative humidity. The mechanism for film stability near the eutectic was studied by x‐ray photoelectron spectroscopy and depth profiling using ion scattering spectroscopy. We found that a Cu‐enriched surface oxide, formed at ambient conditions, passivates the film and is responsible for its subsequent stability after accelerated aging. We also demonstrated that a 14 in. diam, multilayer optical disk with a Te65 Cu35 recording medium exhibits excellent linearity for 3 and 8 MHz pulses, good written pulse length stability, and high signal‐to‐noise ratio....