Observation of oscillations in the transport for atomic layer MoS2

In our experiment, an atomic layer MoS2 structure grown on SiO2/Si substrates is used in transport test. The voltage U-14,U-23 oscillates and the corresponding period varies with applied current. The largest period appears at 45 mu A. The oscillation periods are different when samples are under laser radiation or in darkness. We discover that under the laser irradiation, the oscillation period occurs at lower current than in the darkness case. Meanwhile, the drift velocity is estimated at similar to 10(7) cm/s. Besides, by studying the envelope of U-14,U-23 versus applied current, we see a beating phenomenon at a certain current value. The beating period in darkness is larger than under laser irradiation. The difference between beating periods reveals the energy difference of electrons. Similar results are obtained by using different laser power densities and different light sources. The possible mechanism behind the oscillation period is discussed.