Molybdenum disulfide(MoS2)has widely used in the fields of lubricants,catalysis,energy storage,composite materials owing to its unique layered structure[1;2].Especially,MoS2 could be transferred from indirect to direct bandgap when its thickness decreased to single layer(only 0.65 nm),which was considered to be the optimum candidate for optoelectronic and nanoelectronic devices[3].