Photo-sensing Based On Two-Dimensional Molybdenum Ditelluride

Since the discovery of graphene in 2004,Two-dimensional materials have been investigated extensively due to their unique physical and chemical properties.Molybdenum ditelluride(MoTe₂)has been widely used in high-performance electronic devices and photodetectors because of its suitable bandgap and controllable polarity.At present,the optoelectronic devices based on MoTe₂ and its heterostructures have achieved remarkable progress while their detection sensitivity,spectral response range and polarity tunable performance still need to be further improved.According to the points above,two heterostructures,molybdenum ditelluride/molybdenum sulfide(MoTe₂/MoS₂)and graphene/molybdenum ditelluride/graphene(G/MoTe₂/G)have been investigated in this paper.Adjustable photoresponsivity and wide spectral detection range are realized.The main research contents are as follows:1.MoTe₂/MoS₂ heterojunction device was constructed and the effect of rapid thermal annealing(RTA)on its electrical properties was studied.The research shows that the polarity of MoTe₂ was gradually changed from bipolar to p-type with the increase of annealing temperature.The polarity of MoTe₂/MoS₂ heterojunction changed with it and finally presented a special behavior of anti-ambipolar.In this process,the polarity of heterojunction can be precisely controlled by RTA temperature.2.The optical performance of MoTe₂/MoS₂ heterojunction photodetector before and after annealing was tested.The reasons for the improvement of the optical performance were analyzed.The performance of the photodetector can be improved by RTA treatment.Besides,the photocurrent was tunable with back gate voltage.The gain and switch of the detector can be actively regulated.3.Graphene was used as the contact electrodes of MoTe₂ and the G/MoTe₂/G heterojunction with horizontal and vertical structure were fabricated.The difference of the performance between the metal electrodes and graphene electrodes was investigated.The results show that the method using graphene as contact electrodes can effectively improve the photodetection property of MoTe₂ FET and realize the optical detection of visible to near-infrared bands.