Influence of temperature on the CuIn_1-xGa_xSe₂films deposited by picosecond laser ablation

Graphical abstract: CIGS films were obtained by picosecond laser ablation at deposition temperatures higher than 200 °C. They are very compact in cross section presenting a columnar structure. Refractive index decreased with increasing the deposition temperature. - Highlights: • CIGS films were deposited on glass substrates by picosecond laser ablation. • The influence of temperature on the film characteristics was investigated. • Picosecond laser ablation proved a suitable method for obtaining of CIGS films. - Abstract: The goal of this study is to investigate the influence of the deposition temperature on the CuIn_1-xGa_xSe₂ (CIGS-copper indium gallium diselenide) film characteristics deposited by picosecond laser ablation method using a Nd:YVO₄ laser (8 ps, 0.2 W, 50 kHz, 532 nm; 5.7 mJ/cm²; 36 × 10⁷ pulses). The films were deposited starting from a CuIn_0.7Ga_0.3Se₂ target, in vacuum at 3 × 10⁻⁵ Torr for 2 h, at room temperature (RT) and 100/200/300/400 °C substrate temperature; as substrate, optical glass was used. Structure, film morphology, composition and optical properties were investigated by X ray diffraction, scanning electron microscopy (energy dispersive X ray spectroscopy), spectroscopic ellipsometry and optical spectrophotometry. CIGS crystalline films have the dominant peak corresponding to (112) direction more pronounced starting with 200 °C deposition temperature. The thickness gradually decreased with temperature increasing, being 1.44 μm at RT and 0.72 μm at 400 °C; atomic composition in the case of In, Ga, Se increased after annealing, while in the case of Cu it decreased comparing with RT; refractive indices exhibited a short decreasing tendency by increasing the deposition temperature, while the optical band gap values for CuIn_0.7Ga_0.3Se₂ laser ablated thin films increased.