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Lithium aluminum silicate glass system (LAS) implanted with chromium ions is prepared. The reflectance and transmittance measurements are used to determine the dispersion of absorption coefficient. The optical data are explained in terms of the different oxidation states adopted by the chromium ions into the glass network. It is found that the oxidation state of the chromium depends on its concentration. Across a wide spectral range, 0.2–1.6μm, analysis of the fundamental absorption edge provides values for the average energy band gaps for allowed direct and indirect transitions. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. Such tail is decreased with the increase of the chromium dopant. From the analysis of the optical absorption data, the absorption peak at ground state exciton energy, the absorption at band gap, and the free exciton binding energy are determined. The extinction coefficient data are used to determine the Fermi energy level of the studied glasses. The metallization criterion is obtained and discussed exploring the nature of the glasses. The measured IR spectra of the different glasses are used to throw some light on the optical properties of the present glasses correlating them with their structure and composition.

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The ac and dc conductivities (σ ac and σ dc ) of amorphous semiconductor Sm doped Se (namely, SeSm 0.005 ) films, prepared by thermal evaporation, were measured under vacuum in a wide range of frequency and temperature. The ac conductivity versus frequency plots were analysed by considering a power law: σ ac ∝ ω s (s 1). A comparison between values of the index s with those numerically calculated from different conduction models reveals that correlated barrier hopping (CBH) is a fairly good model to describe the dominant ac conduction mechanism. The concept of the Meyer-Neldel (MN) rule in the expression of the relaxation time is considered for both ac and dc experimental data. The validity of the CBH model based on the MN (normal and inverted) rule is studied and discussed. Besides, results of the real dielectric constant (ε ), loss factor (ε ) and loss tangent (tan δ) together with the Cole-Cole diagrams and the optical (ε ∞ ) and static (ε s ) dielectric constants for a-SeSm 0.005 films are given and discussed.

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