Optical characterization of defect chalcopyrite ZnIn2Te4 thin films for opto-electronic device implementations

Defect chalcopyrite compounds have emerged as promising materials for optoelectronic applications. In this study, we investigate the linear and nonlinear optical properties of ZnIn₂Te₄ thin films deposited with varying thicknesses (113–385 nm). The transmittance and reflectance measurements were performed across a wide spectral range (400–2500 nm), revealing two distinct optical band gaps of 0.932 eV (indirect) and 1.36 eV (direct). The refractive index \(n\) and extinction coefficient \(k\) exhibited normal dispersion behavior. While the skin depth decreased and optical conductivity increased with photon energy. Using the Wemple–DiDomenico single oscillator model, we extracted key optical parameters such as the oscillator energy \({E}_{o}\), dispersion energy \({E}_{d}\), infinite dielectric constant \({\varepsilon }_{\infty }\), and oscillator strength \({S}_{o}\). Energy loss functions (\(\text{VELF}\) and \(\text{SELF}\)) also increased with photon energy. Nonlinear optical properties, including the linear susceptibility \({\chi }^{(1)}\), third-order susceptibility \({\chi }^{(3)}\), and nonlinear refractive index \({n}_{2}\), were evaluated, yielding values of 0.944, 1.35 × 10⁻¹⁰ \(esu\), and 1.42 × 10⁻⁹ \(esu\), respectively. These results demonstrate the potential of ZnIn₂Te₄ for use in optical devices such as filters, photodetectors, and nonlinear switches.

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