Electrical conductivity and dielectric properties of bulk glass Se55Ge30As15 chalcogenide

Measurements of conductivity (AC and DC), dielectric constant ε′(ω) and dielectric loss ε′′(ω) have been made for bulk glassy samples of Se55Ge30As15 alloy in the frequency range from 10 kHz to 10 MHz and within the temperature range from 350 to 500 K. The DC conductivity shows an activated behavior above 370 K, giving a conduction activation energy ΔE=0.83 eV. The AC conductivity σac (ω) was found to be temperature independent and vary as ωs with s=0.994, where s is the frequency exponent. The charge-transfer process explained via CBH model with centers of intimate valence alternation pairs (IVAPs) type, giving a maximum barrier height WM=2.23 eV and density of localized states N (EF)=1.67×1020 cm−3. The dielectric constants behavior, reveal that the tested bulk Se55Ge30As15 chalcogenide exists in the form of molecular dipoles which remain frozen at low temperatures and, as the temperature is increased, the molecules attain freedom of rotation at temperatures above 370 K. The experimental results also gave a direct evidence of the existence of a Debye-type relaxation having a wide distribution of relaxation times. The most probable value of a spread of relaxation times have been estimated as τ=4.13×10−6 s.