Electronic conduction in MeV energy ion-beam irradiated semiconducting glass Pb₂₀Ge₁₉Se₆₁

Abstract

The semiconducting glass Pb₂₀Ge₁₉Se₆₁ has been irradiated with a 75 MeV ⁵⁸Ni⁶⁺ ion-beam at room temperature with fluences 2 × 10¹³ and 5 × 10¹³ ions/cm². Irradiation-induced effects on the electronic conduction process in the bombarded and sequentially annealed (at 100–220°C) semiconductor have been investigated by measurements of the temperature dependence of the d.c. conductivity, and frequency (100Hz-10kHz) and temperature dependence of the a.c. conductivity and dielectric relaxation in the temperature span 180K-450K. An analysis of the data revealed that the Ni-ion induced defects/complexes in the bombarded semiconductor become electrically active on annealing and introduce localized states near the Fermi level which exhibit variable-range hopping conduction. Irradiation and subsequent annealing introduces inhomogeneity into the semiconductor with a distribution of simple defects and clusters in the bulk of the material. The results of a.c. conductivity and dielectric relaxation support this view. It is interesting to observe that a transition metal impurity like Ni, having an incomplete electronic d-shell, when added in a small concentration (≊ 0·2 at.% at a dose of 2 × 10¹³ ions/cm²) by ion-bombardment into the glassy semiconductor, can produce remarkable changes in the electronic transport properties.