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This work clarifies the origin of the characteristic discontinuities registered during the deformation of the (101̄0) plane of sapphire, by means of depth sensing indentation experiments with a spherical indenter. The sudden increase of the plasticity of the crystal was found to be caused by a twinning process. The calculation and analysis of the distribution of resolved shear stresses under a spherical indenter predicted the features of the surface deformation. The high resolution microscopic examination of the residual impressions confirmed the theoretical prediction.

To understand the nature of Ag-rich chalcogenide glasses, the optical, electrical, and structural properties of evaporated amorphous (Ge0.3S0.7)100−xAgx and (Ge0.3Se0.7)100−yAgy films have been examined and compared with each other over a wide compositional range in Ag content. The maximum Ag content for the amorphous films was 67 at. % for the S-based system and 40 at. % for the Se-based system. The physical properties of both systems depended significantly on the Ag content but the compositional trends resembled each other. All the photoinduced and thermally induced phenomena observed for the S-based system were also observed for the Se-based system but with the compositional ranges shifted to lower Ag concentration: the photo- and thermal bleachings (0≤y<22 for the Se-based system, 0≤x<40 for the S-based system), the photoinduced surface deposition (PSD) of metallic Ag phenomenon, and the phase separation on annealing (25<y≤40, 50<x≤67). The Se-based system was found to exhibit the PSD phenomenon at low Ag concentrations where the S-based system never exhibits this effect.