For cost-effective synthesis of Cu2FeSnS4 (CFTS) thin films, a chemical bath deposition technique was carried out at temperature of 343 K. The formation of tetragonal phase and highly oriented CFTS thin films was confirmed by XRD technique. The morphology and composition of the CFTS thin films were characterized by field emission scanning electron microscopy and EDX techniques. Linear and nonlinear optical studies of the CFTS thin films were executed to determine a future device application. The chemically prepared CFTS thin films reveal a direct energy gap which decreased from 1.54 to 1.31 eV with increasing the thickness. The nonlinear optical constants of the chemically prepared CFTS thin films such as the nonlinear absorption coefficient βc, the nonlinear refractive index n2 and the third-order susceptibility χ(3) were evaluated and analysed.

中文翻译：

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Cu2FeSnS4球形纳米结构薄膜的线性和非线性光学行为的制备和生长

为了经济有效地合成 Cu2FeSnS4 (CFTS) 薄膜，在 343 K 的温度下进行了化学浴沉积技术。 XRD 技术证实了四方相和高度取向的 CFTS 薄膜的形成。CFTS 薄膜的形态和成分通过场发射扫描电子显微镜和 EDX 技术进行表征。对 CFTS 薄膜进行了线性和非线性光学研究，以确定未来的设备应用。化学制备的 CFTS 薄膜显示出直接能隙，随着厚度的增加，其从 1.54 eV 减小到 1.31 eV。评估和分析了化学制备的CFTS薄膜的非线性光学常数，如非线性吸收系数βc、非线性折射率n2和三阶磁化率χ(3)。