Local structural and optical properties of GeSb phase-change materials

Local structural variation of Ge x Sb 1− x and (GeSb)Si alloy films was studied by extended X-ray absorption fine structure (EXAFS). From X-ray diffraction result, the as-deposited Ge x Sb 1− x alloy films consisted of amorphous phase but the analysis of Fourier transformed Ge K-edge EXAFS spectra indicated that the nearest neighbor of Ge atoms was changed with Ge content. The crystalline Ge x Sb 1− x films obtained by annealing showed the presence of Ge crystalline phase in GeSb solid solution. The calculated interatomic distance between Ge atoms for crystalline GeSb films was similar to that of pure Ge film. The optical reflectivity increased with decrease of Ge content and the Ge rich composition caused slow crystallization time. The effect of Si addition in GeSb alloy was also analysed.