Structural, Optical and Optoelectrical Properties of CuAlSnS4 Thin Films

The present study used chemical deposition to deposit thin copper aluminum tin sulfide (CATS(4)) layers onto clean glass substrates. X-ray diffraction analysis was utilized to explore the crystalline structure of the CATS4 films, which refers to the CATS(4) films having a cubic crystal structure. Energy-dispersive X-ray analysis showed the presence of Cu, Al, Sn, and S peaks in the CATS(4) 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 CATS(4) layers. The CATS(4) 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 CATS(4) films. The inspected CATS(4) 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 CATS(4) films increased their nonlinear optical indices. Additionally, the hot probe apparatus verified the p-type semiconducting characteristics of CATS(4) films.