MoS 2 Thin Films Grown by Sulfurization of DC Sputtered Mo Thin Films on Si/SiO 2 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 °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 E12g and A1g of hexagonal phase MoS2 was determined as ~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 3d5/2 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 analysis. Therefore, it is considered that the films can be used for photodetector applications in these regions and also for infrared shielding coating applications.