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Semiconductor Physics, Quantum Electronics & Optoelectronics. 2013. V. 16, N 1. P. 076-079.
Interband absorption and its relation
to the electronic structure of Co-Cr solid solutions
Taras Shevchenko Kyiv National University, Physics Department, Chair of Optics,
64, Volodymyrska str., Kyiv 01601, Ukraine
E-mail: bond270587@i.ua
Abstract. The refraction n and absorption χ indices of paramagnetic Сo-Cr alloys with 10, 20 and 35% chromium concentrations were measured within the spectral range 0.23 to 2.8 µm (0.44…5.36 eV) at room temperature by spectral ellipsometric methods. Based on these data, the dielectric permittivity ε, optical conductivity σ and reflection coefficient R at normal incidence were calculated. The dispersion of optical conductivity σ(hν) and dispersion curves of residual optical conductivity Δσ(hν) = σ(hν) – (1 – c)xσCo(hν) were analyzed in detail (c – Cr impurity concentration, σCo(hν) – optical conductivity of Co solvent). It has been ascertained that new impurity bands are formed in the electronic spectrum of Co solvent when Cr impurities are added, which are responsible for the extra absorption in Сo-Cr alloys. The localization of impurity energy levels in Co-Cr alloys at 1.8…2.0 eV above the Fermi level has been suggested. Keywords: Co-Cr alloy, electronic structure, impurity band, energy subband, electron density, interband transition, density of electron states, optical conductivity spectrum.
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