Optical properties of as-deposited, annealed and laser-treated Ge2Sb2Te5 thin films

Abstract

Knowledge of the correct optical properties of phase change materials (PCM) is important in the development of many devices. Here, we report on the differences in optical properties of as-deposited, annealed, laser-reamorphized and laser-recrystallized G e 2 S b 2 T e 5 thin films. While as-deposited and laser-reamorphized G e 2 S b 2 T e 5 show a similar spectral dependences of refractive indices and extinction coefficients with a small decrease in optical band gap from 0.63 to 0.59 eV, spectral dependences of annealed and laser-recrystallized G e 2 S b 2 T e 5 differ significantly from each other in the entire measured spectral region with values of optical band gap 0.51 and 0.45 eV, respectively. We discuss the main differences in the optical functions between both crystalline phases using X-ray diffraction studies. We further present that the laser-reamorphized phase transforms to the crystalline phase at about 12 °C lower temperature in contrast to the as-deposited amorphous phase.