New phase change material for optical recording with short erase time

Abstract

We present data on a new erasable phase change medium, demonstrating for the first time that very short erase times can be obtained without sacrificing room-temperature stability of the amorphous state. Thin films of the composition Sb2Se underwent 10% relative reflectivity changes when switched with a laser between amorphous and crystalline states. Twenty milliwatt, 50 ns laser pulses were used for writing amorphous spots; 6.9 mW, 200 ns pulses were used for erasing. A playback carrier to noise ratio of 43 dB was observed on a plastic disk. Amorphous spots could be heated in a microscope to 175°C before they crystallized. Transmission electron microscopy and x-ray diffraction indicate that the erased state is single phase and polycrystalline. The crystal structure, however, does not correspond to known compounds in the antimony-selenium system.