Phase Transition of GeSbTe Thin Films Induced by Thermal Treatment and Laser Irradiation

Abstract

GeSbTe (GST) thin films were deposited on Si substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures. X-ray diffraction (XRD) and Atomic Force Microscope (AFM) measurements were used to characterize as-deposited and annealed films. Annealing treatment was found to induce changes in microstructure, surface roughness, grain size and so on, indicating that with the increase of annealing temperature, the amorphous state of GST materials change first to face-centered-cubic (fcc) phase state and finally to the stable hexagonal (hex) state. Amorphous Ge1Sb2Te4film will crystallize under laser irradiation. With increasing irradiation time or irradiation power, the degree of crystallization increases. The Raman spectra of thin film shows three peaks after laser irradiation, the peaks can be attributed to the key vibrations which were caused by crystallization. With the irradiation time increases, the peaks shift.