Structural, Optical and Optoelectrical Properties of CuAlSnS4 Thin Films

The present study used chemical deposition to deposit thin copper aluminum tin sulfide (CATS₄) layers onto clean glass substrates. X-ray diffraction analysis was utilized to explore the crystalline structure of the CATS4 films, which refers to the CATS₄ films having a cubic crystal structure. Energy-dispersive X-ray analysis showed the presence of Cu, Al, Sn, and S peaks in the CATS₄ films, and their atomic ratio is close to 1:1:1:4. Spectrophotometric measurements of optical transmittance and reflectance spanning the 400–2500 nm spectral range were performed to describe the optical properties of the CATS₄ layers. The CATS₄ films demonstrated a direct energy gap transition between 1.42 and 1.31 eV. Further, increasing the layer thickness enhanced the refractive index and Urbach energy of the CATS₄ films. The inspected CATS₄ films showed better optoelectrical properties with increasing thickness, including improved optical conductivity, optical resistivity, optical carrier concentration, relaxation time, and optical mobility. Increasing the thickness of the CATS₄ films increased their nonlinear optical indices. Additionally, the hot probe apparatus verified the p-type semiconducting characteristics of CATS₄ films.