Local vibrational and mechanical characterization of Ag conducting chalcogenide glasses

Abstract Macroscopic and local studies of vibrational and mechanical properties of bulk Ag x (Ge 0.25 Se 0.75 ) 100- x glasses were conducted using Raman (mapping) spectroscopy, Vickers microhardness H v and Contact Resonance Atomic Force Microscopy (CR-AFM). For the glass containing 10 at% in Ag, Raman mapping gave evidence of a phase separation through continuous interpenetrating phases (Ag-rich and Ag-poor phases) in the spinodal decomposition process. Combined mechanical characterizations (H v and CR-AFM) indicated that the microhardness and rigidity modulus decrease with the silver content in the glass. At nanoscale level, CR-AFM measurements highlighted a modulation of the rigidity with Ag content. The structural origin of these changes was confirmed using Raman mapping evidencing modifications in the tetrahedral network between two phases. The results could suggest a different Ge/Se ratio in Ag-poor and Ag-rich phases. To further investigate the liquid-liquid phase separation morphology, small angle neutron scattering was performed at different temperatures in the liquid state. Whereas liquids with 15 and 25 at% in Ag showed a nucleation/growth morphology for all studied liquid temperatures, a spinodal decomposition with fractal dimension D from 2.6 to 3.4 was found for 5 at% in Ag when the temperature increases from 600 °C to 700 °C.