MoS2 Thin Films Grown by Sulfurization of DC Sputtered Mo Thin Films on Si/SiO2 and C-Plane Sapphire Substrates

Abstract

Here we report the growth of molybdenum disulfide (MoS2) films with different thicknesses on silicon dioxide/silicon (SiO2/Si) and c-plane sapphire substrates by sulfurization of direct current (DC) sputtered Mo precursor films in a chemical vapor deposition furnace with sulfur powder at 900 degrees C. The structural, morphological, optical, and electrical properties of the films on different substrates were investigated through a series of characterization in detail. X-ray diffraction (XRD) results showed that the grown films on sapphire substrates had better crystallization and a well-stacked layered structure than the films on SiO2/Si substrates. The frequency difference between the characteristic modes E-2g(1) and A(1g) of hexagonal phase MoS2 was determined as similar to 26 cm(-1) which is consistent with the typical value of bulk MoS2. Energy-dispersive x-ray (EDX) spectra exhibited that the films were near-stoichiometric. A small shift towards the lower binding energies in the Mo 3d(5/2) peak positions was observed due to the valency of Mo below +4 depending on the compositional ratios of the films in x-ray photoelectron spectroscopy (XPS) spectra. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis indicated that the films had smooth surfaces and a well-packed crystal structure. However, when the thickness of the films deposited on sapphire substrates increased, the strain between the sapphire substrate and MoS2 film caused the formation of the micro-domes in the film. In addition, the films exhibited high absorption and reflection properties in the near-infrared (NIR) and mid-infrared (MIR) regions in Fourier transform infrared (FTIR) analysis. Therefore, it is considered that the films can be used for photodetector applications in these regions and infrared shielding coating applications.