Structural, optical, electrical, and low temperature thermoelectric studies on the ordered vacancy compound AgGa3Se5

Abstract

AbstractPolycrystalline thin films of the ordered vacancy compound AgGa3Se5 were prepared by a multisource vacuum coevaporation technique at a substrate temperature of 623 K. X‐ray diffraction and atomic force microscopy in conjunction with energy‐dispersive analysis of X‐rays and X‐ray photoelectron spectroscopy were used for the structural, morphological, and compositional characterization. The distortion parameter and the anion displacement deduced from the X‐ray diffraction data using the CTB plus η = ηtet rule were used for obtaining the anion–cation bond lengths. The compound manifested a slight increase in the nonideal anion displacement compared to AgGaSe2. The films with ternary chalcopyrite structure were found to possess an enhanced direct allowed bandgap of ∼1.8 eV compared to that in AgGaSe2 indicative of the slightly reduced p–d interband repulsion due to the periodic introduction of silver vacancies. The electrical resistivity was assessed to be of the order of 10−1 Ω m with n‐type conductivity and the films exhibited good photosensitivity. An unusual increase in Seebeck coefficient was manifested in the low‐temperature range 4–330 K with negligible phonon drag toward the very low and room temperature regime.