Electrical and thermoelectric properties of ternary Cu-Ge-Te films

Abstract

Chalcogenides are motivating members of crystalline and/or amorphous materials because of their use in many application devices as optoelectronics, detectors of thermally imaging, optical waveguides, recording materials, solar cells, bio- and chemical-sensors. Bulk samples for ternary Ge26CuxTe74−x(2.5≤x≤12.5at.%) glasses were prepared using the well-known melt quenching method. Thermal evaporation method has been used to prepare thin films. The amorphous state of the prepared films was confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The dark dc-electrical conductivity (σdc) and Seebeck coefficient (S) were measured over an extensive range of temperature (300–450 K). The activation energies for electrical conduction (ΔEdc) and thermoelectric effect (ΔEs) decrease with an increase of Cu content. This reflects the observed increase in the carrier concentrations (nσ for electrical conduction and ns for thermoelectric). With the addition of Cu content, the defects as the weak Te–Te homopolar ponds (1.43 eV) increase which may tend to lower the energy of the conduction-band edge. Consequentially, both of the ΔEdc and the optical band gap (Eg) decrease with the increase in Cu content. The obtained results for the dc conductivity and the Seebeck coefficient may lead to a high value of the power factor. The current study is carried out to obtain high-efficient films for their using in the potential applications of thermoelectric phenomenon by an easy, simple, and low economic cost methods. A good correlation between the activation energy for electric conduction (ΔEdc) and the glass transition temperature (Tg) has been established.