Influence of Pulse Laser Deposition on the Structural and Optical Properties of CZTS for Sensor Applications

Abstract

In this study, CZTS (Copper Zinc Tin Sulfide) thin films were fabricated using the pulse laser deposition (PLD) technique. Pellets formed under a pressure of 5 tons were ablated with a Nd:YAG laser at a pulse energy of 700 mJ. The resulting plasma plume was generated through a range of pulse counts-200, 250, 300, 350, and 400-at a consistent frequency of 6 Hz. The structural properties of the films were investigated via X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD analysis revealed a polycrystalline tetragonal structure of the CZTS thin films, with an increase in peak quantity correlating to higher pulse counts. Concurrently, variations in grain size, strain, dislocation density, and lattice constants (a, c) manifested an irregular pattern as a function of pulse count. AFM assessments-comprising parameters such as root-mean-square (RMS) roughness, average diameter, and arithmetic mean height-indicated a peak in surface roughness at the maximum pulse quantity of 400. Optical properties were characterized using a UV-Visible Spectrophotometer (2700) across a spectrum ranging from 300 to 1100 nm. An increment in absorbance was noted with the rise in pulse number, whereas the direct bandgap exhibited a decrease from 3.6 to 2.8 eV. The films demonstrated exceptional potential for sensor applications, evidenced by transmittance levels exceeding 90%. Optical constants, including refractive index and extinction coefficient, were derived from the spectral data. The comprehensive analysis suggests that by manipulating the pulse count during PLD, not only can the structural properties of CZTS thin films be tailored, but their optical attributes can be optimized, paving the way for advanced applications in photonic sensors and other optoelectronic devices.