Influence of pH on the Structural and Optical Properties of Polycrystalline MnTe₂ Thin Films Produced by Chemical Bath Deposition Method

Polycrystalline manganese ditelluride (MnTe₂) thin films are synthesized on commercial glass substrates by chemical bath deposition technique at different pH values (pH = 9, 10, 11 and 12). The effect of pH on the structural and optical properties of chemically deposited MnTe₂ thin films have been investigated in this study. The structure and optical properties of the films are characterized by X-ray diffraction and optical absorption spectroscopy. The X-ray diffraction results suggest that the films are polycrystalline with a mixture of dominant cubic MnTe₂ phase and few traces of orthorhombic MnTeO₃ and MnTe₂O₅ phases. The optical band gap of the films increases approximately from 1.66 eV to 2.62 eV with increasing pH. Moreover, optical parameters of the films such as refractive index, extinction coefficient, real and imaginary dielectric constants are investigated using absorption and transmittance spectra taken from the UV-vis spectrophotometer. At 600 nm wavelength, refractive index and extinction coefficient values vary in the range of 1.39-1.55 and 0.17-0.23, respectively. An increase in optical band gap could be attributed to the quantum confinement effect.