Effect of substrate and substrate temperature on the deposition of MoS2 by radio frequency magnetron sputtering

Abstract

Radio frequency magnetron sputtering is considered as one of the efficient methods to develop large area homogeneous 2D MoS2 on quartz substrates. The application of MoS2 in products, such as transistors, solar cells, photodetectors, chemical sensors, valleytronics, and spintronic devices demands the deposition on a wide variety of substrates. Here, we are examining whether a one step preparation method of sputtering of the molybdenum metal in a sulfur sufficient environment will provide a universal strategy to develop 2D MoS2 on any substrates. The dependence of the deposition on substrate temperature is also studied. On all of the substrates we used (quartz, c-plane sapphire, p-type silicon, and silicon dioxide), uniform coating of 2D MoS2 was confirmed with the presence of E12g and A1g, the Raman signature peaks. Both the Raman shift difference A1g–E12g and atomic force microscopy helped in determining the varying thicknesses of the samples. Hexalayer to bilayer MoS2 were formed when the substrate temperature was increased from 600 to 800 °C, confirming that a higher substrate temperature is needed for producing thinner samples. Absorbance spectra of the samples sputtered on quartz displayed the A, B and convoluted C and D excitonic peaks of 2H-MoS2. Only the samples prepared at higher substrate temperatures yielded a photoluminescence spectrum indicating the formation of trilayer and bilayer MoS2. Optical images and AFM measurements revealed a uniform coating over the entire substrate area. Thus, the one step method of simultaneous sputtering and evaporation proved to be a universal method for developing MoS2 thin films on any kind of substrates.