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Phase-Change Nanodot Material for an Optical Memory



A sputtered phase-change material, Ge10Sb90, processed into dots with a height and diameter of 50 nm, shows rapid crystallization triggered by 300 ps laser excitation. Crystallization takes place with a short time delay of approximately 70 ns for a sample with Sb seed layers. The delay becomes just 15–20 ns when a NiCr layer is provided to control the heating–cooling profile. The nanodot sample requires less energy for crystallization, with a large optical change equivalent to that of the blanket film. These results demonstrate that the nanodot phase-change material could be a possible candidate for next-generation “green” optical storage.