The fractional change in reflectivity due to temperature ΔR/R of bulk samples of four silver-cadmium alloys was measured in the energy range (2.2÷4.8) eV. The samples had cadmium concentrations of 1.5, 3.0, 6.5 and 15 at. %. The temperature-induced changes of the imaginary parts of the complex dielectric constant De2 2were calculated by means of an analytical model previously developed by one of the authors. Using the optical gaps at the symmetry pointL as adjustable parameters, we have reconstructed the experimental ΔR/R spectra with good results. This has allowed us to determine with substantially increased accuracy over previous alloy work the dependence of theL′2(E F)−L 1 andL 3−L′2(E F) absorption edges and of theL′2−L 1 critical pointvs. solute concentration. In particular we find for theL′2(E F)−L 1 absorption edge the same slopevs. concentration already determined by Flaten and Stern, but the absolute values are consistently higher by almost 0.5 eV. Also interesting is the behaviour of theL 3 L′2(E F) absorption, edge which shows at first a slight decreasevs. solute concentration which is the opposite of what is predicted by the rigid-band model.
Optical gaps of dilute α-phase Ag-Cd alloys from thermoreflectance measurements
MODESTI, SILVIO;
1977-01-01
Abstract
The fractional change in reflectivity due to temperature ΔR/R of bulk samples of four silver-cadmium alloys was measured in the energy range (2.2÷4.8) eV. The samples had cadmium concentrations of 1.5, 3.0, 6.5 and 15 at. %. The temperature-induced changes of the imaginary parts of the complex dielectric constant De2 2were calculated by means of an analytical model previously developed by one of the authors. Using the optical gaps at the symmetry pointL as adjustable parameters, we have reconstructed the experimental ΔR/R spectra with good results. This has allowed us to determine with substantially increased accuracy over previous alloy work the dependence of theL′2(E F)−L 1 andL 3−L′2(E F) absorption edges and of theL′2−L 1 critical pointvs. solute concentration. In particular we find for theL′2(E F)−L 1 absorption edge the same slopevs. concentration already determined by Flaten and Stern, but the absolute values are consistently higher by almost 0.5 eV. Also interesting is the behaviour of theL 3 L′2(E F) absorption, edge which shows at first a slight decreasevs. solute concentration which is the opposite of what is predicted by the rigid-band model.Pubblicazioni consigliate
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