Temperature and frequency dependence outline of DC electrical conductivity, dielectric constants, and AC electrical conductivity in nanostructured TlInS2 thin films

Recently, chalcogenides materials that containing sulfur, S, have attracted scientists attention for using as active recording films in programmable metallization cell memory (PMC) devices. Thus, in the present work a nanostructured TlInS₂ thin film is prepared by using thermal evaporation and is characterized via X-ray diffractometer (XRD) and transmission electron microscope (TEM). Based on XRD calculations and TEM micrograph, the as-deposited thin film shows nanostructure of average particle size equals to 50 ± 4 nm. Subsequently, a device of the structure Au/TlInS₂/Au is fabricated using thermal evaporation and is investigated by using impedance spectroscopy. The DC electrical conductivity is carried out in the temperature range of 358–468 K. The AC electrical and dielectric properties are measured in the dark conditions and their dependence on the temperature (373–473 K) and the frequency (0.5–200 kHz) is discussed. Of these, the σ_ac increases as the temperature increases and it obeys the universal power law σ_ac = Aω^s. Also, the dielectric constants show high values at high temperatures due to the presence of interface charges that is formed at the interfacial surface between the gold electrode and TlInS₂ NPs. Moreover, the real part of the dielectric modulus M' reveals low values at low frequencies and it increases as frequency increases and this is interpreted in terms of the disability of driving forces (at low frequencies) which governs the mobility of charge carriers under the influence of the electric field.