This work reports the phase-change behavior and thermal stability of doped GeSbTe/GeSbTe bilayers. We prepared the bilayers using RF sputtering, and annealed them at annealing temperature ranging from 100℃ to 400℃. The sheet resistance of the bilayer decreased and saturated with increasing annealing temperature, and the saturated value was close to that of pure GeSbTe film. The surface of the bilayer roughened at 400℃, which corresponds to the surface roughening of doped GeSbTe film. Mixed phases of face-centered cubic and hexagonal close-packed crystalline structures were identified in the bilayers annealed at elevated temperature. These results indicate that the phase-change behavior of the bilayer depends on the concurrent phase-transitions of the two GeSbTe-based films. The dopants in the doped GeSbTe film were diffused out at annealing temperatures of 300℃ or higher, which implies that the thermal stability of the bilayer should be considered for its application in phase-change electronic devices.

An amorphous Ge2Sb2Te5 thin film is one of the most commonly used materials for phase-change data storage. In this study, Aux(Ge2Sb2Te5)1-x thin film amorphous-to-crystalline phase-change rate were evaluated in using 658 nm laser beam. The focused laser beam with a diameter <10 μm was illuminated in the power (P) and pulse duration (t) ranges of 1-17 mW and 10-460 ns, respectively, with subsequent detection of the responsive signals reflected from the film surface. We also evaluated the material characteristics, such as optical absorption and energy gap, crystalline phases, and sheet resistance of as-deposited and annealed films. The result of experiments showed that the thermal stability of the Ge2Sb2Te5 film is largely improved by adding Au.