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_14,23 oscillates and the corresponding period varies with applied current. The largest period appears at 45 μA. 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~10⁷ cm/s. Besides, by studying the envelope of U_14,23 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.