Measurement of the thermal coefficients of erasable phase-change media

A new method was developed for determining the thermal coefficients of erasable phase change films. The method consists of monitoring the reflectivity variations of a PC sample during the writing process. The system uses a 1.7 μs laser pulse at a fixed power level to create a hot spot under the focused beam, while simultaneously observing the reflectivity variations. The amount of reflected light does not increase initially after the laser has been turned on; there is a knee in each curve that corresponds to the onset of noticeable reflectivity change. Two single layer PC samples were measured using this technique: one was a 35 nm-thick sample and the other was 90 mm thick, both coated on identical glass substrate.