Optical characterization of MoS2 and MoS2/Zn synthesized by thermal evaporation and sol-gel spin-coating techniques for gas-sensing and NLO-applications

Thermal evaporation and sol-gel spin coating techniques were utilized to fabricate different (MoS2)1-x Znx (x = 0, 0.03) films for gas sensing and nonlinear optical applications. X-ray diffraction, field emission scanning electron microscope (FE–SEM) and energy dispersive x-ray spectroscopy were utilized to investigate their structural, morphological, and elemental analyses. Besides, the optical and electrical characterizations were studied using UV/VIS/NIR spectrophotometers, Fourier transform infrared spectroscopy (FTIR) and two probe technique, respectively. (MoS2)1-x Znx (x = 0, 0.03) films prepared by thermal evaporation or sol-gel spin coating were amorphous or polycrystalline structure, respectively. Different Mo–S, S–S and Zn–S bonds are existed in the films. The highest non-linear refractive index of 5.71 × 10−10 esu and third order polarizability of 4.822 × 10−11 esu have been attained by the thermally deposited film of 300 nm thickness, among others. The NH3 gas sensing process by MoS2 and Zn: MoS2 films are reversible with short response and recovery times of 30-10 & 25-9 and 7–30 & 11-4 s at the NH3 gas concentration of 50–250 ppm, respectively. Such sensing process are repeatable.