First-principles Study Of Se Atom Regulating Schottky Barrier In MoS₂ Heterostructures

Field effect transistor（FET）based on 2D nano material heterostructures has attracted extensive attention due to its great advantages of high input resistance,easy integration,low noise,large dynamic range,low power consumption,and wide safe working area.It is a very promising power electronic device.Transition metal chalcogenides such as MoS₂ have are ideal candidates for FET devices because they can reduce the short channel effect due to the absence of suspension bonds on the surface.However,the schottky barrier formed by electron injection greatly limits the performance of FET,and contact resistance is one of the key factors leading to mobility loss.One of the most basic and challenging tasks to achieve the high performance of ultra-thin FET is to obtain an extremely low or even zero Schottky barrier height（SBH）at the source/drain contact.Therefore,this thesis proposes an effective solution:the performance of MoS_xSe_（2-x）/graphene(MoS_xSe_（2-x）/G),MoS_xSe_（2-x）/Al heterostructures based FETs is controlled by changing the Se atom doping concentration,and a two-dimensional heterostructures device with extremely low or even zero Schottky barrier is obtained.The specific contents are as follows:（1）The effects of Se atom doping on the structure,interface interaction and electronic properties of MoS_xSe_（2-x）/G heterostructures were studied by first-principles calculation system.The results show that the type and height of the schottky barrier can be adjusted by different concentrations of Se atoms.When the Se concentration is more than 25%,the type of Schottky barrier changes from n to P.A low p-type schottky barrier is formed at the interface and effective charge transfer is realized due to the increase of Se atom concentration.In addition,the schottky barrier of MoS_xSe_（2-x）/G heterostructure decreases with the increase of applied electric field until it is zero.（2）The effect of Se atomic doping on SBH of MoS_xSe_（2-x）/Al heterostructure has been studied based on Schottky-Mott rule.The results show that due to the influence of Se atom doping,the interaction between metal and MoS₂ and the interface state will be destroyed.With the increasing proportion of Se atom doping,the barrier height of MoS_xSe_（2-x）/Al will gradually decrease.When the doping concentration reaches 50%,the SBH barrier between MoS_xSe_（2-x）/Al is zero according to the Schottky-Mott principle.These results provide a new research direction for the development of high-performance FET with Se atom substitution layer as contact electrode.