Ag-Doped Cu2Se: Tunability of Structural, Optical, and Electrical Properties

Abstract

A successful synthesis of high-purity Cu2−xAgxSe nanopowders (x = 0.03, 0.06, and 0.0.9 mole) was realized through a direct fusion approach. The XRD measurements uncovered the existence of two phases in the Cu2−xAgxSe nanopowders with dominant orientation along the(101) plane.The (101) reflection displayed a monotonical shift towards 2θ angles due to small disfigurement of unit cell originating from the replacement of Cu with Ag. The optical parameters such as absorption coefficient (α), energy band gaps (Eg), extinction coefficients (k), and the refractive index (n) were thoroughly investigated. The values of the energy band gap were found to be 0.78 to 1.5 eV. The increase in the band gap may be due to the decrease in grain size, or the increase in strains. Scanning and transmission electron microscope (SEM) and TEM were used to investigate the morphology of the samples. Cu0.97Ag0.03Se exhibits distinguishable particles and a clear grain boundary, while Cu0.91Ag0.09Se exhibits particles with tetragonal and monoclinic shapes, which supported the presence of two phases-tetragonal CuAgSe and monoclinic −Cu2Se-found in the XRD data. The presence of Ag, Cu, and Se was confirmed by the energy-dispersive X-ray analysis (EDAX). The dielectric characteristics, ac conductivity, and the complex electric modulus were investigated in the frequency range from 0.1 Hz to 10 MHz at temperatures 30 °C and 150 °C.