Two-dimensional semiconductors are promising for the ultimate atomic field-effect transistor (FET) technology after silicon era because of their unique atomic-scale thickness and flatness.However, numerous physical and technological issues have to be addressed before practical use.In this study, the essential physical issues on thickness characterization, carrier injection and scattering mechanisms for MoS2 atomic layers are addressed.First, a rapid and nondestructive layer counting technique for the atomic MoS2 layers is developed by using interference Raman spectroscopy.