Investigation of structural changes in AsxSe100-x amorphous thin films after electron beam irradiation with XAFS, XANES and Kelvin force microscopy

Abstract

Interaction of AsxSe100-x glass thin films with electron beam was investigated by Atomic force microscopy (AFM), Kelvin force microscopy (KFM), X-ray absorption fine-structure (EXAFS) and X-ray-absorption near-edge (XANES). Electron beam induces different surface reliefs depending on the irradiation dose. At doses equal to 7.4*102 μC/cm2 Gausian-like cones are observed. At doses equal to 9.3*107 μC/cm2 craters are formed. We find that film sensitivity to electron beam irradiation correlates with its electrical conductivity. EXAFS measurements indicate that in arsenic rich glasses arsenic coordination number is doubled after e-beam irradiation. XANES data for electron irradiated films show red shifts of absorption edges for three selected glass compositions, which indicate that there is persistent charge accumulated in the glass after e-beam exposure. Red shifts of As-K absorption edges are: 0.7 eV, 1.2 eV and 1.7 eV for As4Se96, As9Se91 and As40Se60 systems respectively. Red shifts of Se-K absorption edges are: 0 eV, 0.6 eV and 1.3 eV for As4Se96, As9Se91 and As40Se60 systems respectively. Observed results indicate that after electron irradiation negative charge is located on arsenic atoms. In arsenic rich glasses, negative charge is also spilled to Se atoms. Charge persistence in electron beam irradiated films is also confirmed by KFM.