Electrical and optoelectronic properties for devices that use MoS2 deposited on Si substrates with and without (NH4)2S x treatment by chemical vapor deposition

Abstract

To fabricate a MoS2/Si device, layers of MoS2 are directly deposited on an n-type Si (n-Si) substrate with/without (NH4)2S x treatment by chemical vapor deposition (CVD). X-ray photoelectron spectroscopy, Hall-effect measurement system, field emission scanning electron microscopy and Raman spectra are employed to characterize the morphology, electrical properties and structure of the MoS2 samples. The MoS2 thin film that is directly deposited on the (NH4)2S x -treated n-Si substrate exhibits n-type behavior and the MoS2/(NH4)2S x -treated n-Si device exhibits stable rectification behavior. It is found that the thermionic emission model is the dominant process in this fabricated MoS2/(NH4)2S x -treated n-Si device. The MoS2/(NH4)2S x -treated n-Si device exhibits high sensitivity to solar irradiation. Because of the value of ideality factor of 1.6 for the MoS2/(NH4)2S x -treated n-Si devices, the enhanced sensitivity is due to the existence of the sulfurated layer at the MoS2/n-Si interface. On the other hand, there were no MoS2 thin films on the n-Si substrate without (NH4)2S x treatment. This observation shows the importance of S–Si bonds on the (NH4)2S x -treated n-Si surface for the CVD growth process. These results demonstrate direct and simple growth of MoS2 on Si, which can be of high importance in future electronic and optoelectronic applications.