Investigation of quenched-in defects in Ge and Si by means of 64Cu

Abstract

For the first time, 64Cu tracer measurements of ionic diffusion were performed for several copper-rich glass compositions in the CuIAs2Se3, CuISbI3As2Se3, CuIPbI2As2Se3, CuIPbI2SbI3As2Se3 and Cu2SeAs2Se3 systems. In accordance with previous a.c. impedance results and Wagner d.c. polarization measurements, it was found that pure Cu+ ion-conducting glasses (50CuI17PbI233As2Se3 and 50CuI20PbI210SbI320As2Se3) exhibit the highest copper tracer diffusion coefficients, DCu, and the lowest diffusion activation energies. The values of DCu at room temperature are higher by 4.5–5.5 orders of magnitude than those in an As2Se3 glass. The Haven ratio, HR, is found to be 0.52–0.61 (ternary glass) and 0.93–1.00 (quaternary glass). Short-range diffusional displacements of the iodide ions induced by the hopping Cu+ ions are also detected in the CuIPbI2SbI3As2Se3 glassy system using 129I-Mössbauer spectroscopy in the temperature range of 4.2 to 305 K. The activation energy of local hopping, Eh ≈ 0.31 eV, is very similar to that of bulk ionic conductivity (0.37 eV) and copper diffusion (≈ 0.33 eV). In contrast to CuI-based vitreous alloys, 50Cu2Se50As2Se3 glass exhibits DCu that are two to five orders of magnitude lower, and the copper ion transport number,tCu+, is between 10−3 and 10−4 in the temperature range 140–170 °C.