OPTICALLY INDUCED PHASE-CHANGES IN AMORPHOUS MATERIALS

The ability to modify the structure of thin films of chalcogenide alloys using light allows the construction of several types of imaging systems, most notably phase change optical memories. The benefits of phase change optical memories include performance and, as a result of the inherent simplicity of the read and write processes, low cost. The key to achieving high speed is the design of an alloy where the crystallization process involves diffusionless crystal growth in a system that does not phase segregate. These materials can be crystallized with laser pulses of 30 ns duration or less, and such high crystallization speeds allow the use of the recording media in the direct-overwrite mode. GeSbTe alloys show excellent characteristics for such application, including fast transition times and excellent stability. Stoichiometric GeTe also shows good performance, but the addition of Sb extends the performance to a wider compositional range, improving manufacturability.