Xueping Li

n- and p-type dopants in the InSe monolayer via substitutional doping

On the basis of density functional theory, we investigate the characteristics of n- and p-type dopants in the InSe monolayer by group V and VII atoms substituting Se atom. The results show that group V and VII atoms substituting Se atom have significant influences on the electronic structures of the InSe monolayer, and all the considered doping cases can be easier to be realized under In-rich experiment conditions. For group V atom-doped InSe monolayer, the magnetic ground states are obtained and its transition levels are too large to provide effective p-type carrier. In contrast, for group VII atom, I atom substituting Se atom has lower formation energy and shallowest transition level, which indicates that I substituting Se atom can induce effective n-type doping in the InSe nanosheets.

Magnetism induced by 3d transition metal atom doping in InSe monolayer

Based on density functional theory, we study the electronic structures and magnetism of 3d transition metal (TM)-doped two-dimensional (2D) InSe monolayer by means of first-principles methods. The results show that all the doping cases can be easily realized under Se-rich experimental environments. For the Sc- and Cu-doped InSe monolayers, the nonmagnetic semiconducting properties can be retained. The Ti-, Cr- and Ni-doped InSe monolayers possess the half-metal behavior. Moreover, the diluted magnetic semiconductor characteristics can be found in the V-, Mn-, Co-, Fe- and Zn-doped cases. Interestingly, the Ti-, V-, Cr- and Fe-doped 2D InSe systems exhibit ferromagnetic ground states, while antiferromagnetic ground states occur in the Mn-, Co- and Ni-doped InSe monolayers.

PtSe2/graphene hetero-multilayer: gate-tunable Schottky barrier height and contact type

Graphene-based two-dimensional hybrid materials are attracting significant attention because they can preserve novel characteristics of Dirac cone. Here, based on first-principles methods, we focus on the electronic characteristics of PtSe2/graphene hetero-multilayer. The negative binding energies indicate that the hybrid materials can be fabricated easily in practice. Also, the n-type Schottky contact is formed and its barrier height is robust to the number of graphene layer. Moreover, the gate-voltage can effectively induce the Schottky barrier transformation from n-type to p-type and contact type transformation from Schottky to Ohmic in the PtSe2/graphene hetero-multilayer. Thus, the work demonstrates that the graphene stacking configuration and gate-voltage will tune the electronic characteristics of PtSe2/graphene-based nanodevices.

Type-II InSe/MoSe2(WSe2) van der Waals heterostructures: vertical strain and electric field effects

Two-dimensional (2D) InSe, a new graphene-like semiconducting material, is gaining significant attention due to its particular optoelectronic characteristics. However, the studies of InSe-based van der Waals heterostructures (vdWHs) are in its initial stages, which limits its applications in future nano-devices. In this work, we utilize first-principles calculations to investigate 2D InSe/MoSe2(WSe2) vdWHs considering stacking configurations, vertical strain and electric field effects. The results show that the most stable 2D InSe/MoSe2(WSe2) vdWHs possess an intrinsic type-II band alignment. Additionally, the vertical strain not only tunes the band gap but also induces the band alignment transition from type-II to type-I in the vdWHs. Besides, application of external electric field can also transfer the intrinsic type-II band alignment to type-I or type-III. This work predicates the feasibility of 2D InSe/MoSe2(WSe2) vdWHs and extends the applications of 2D InSe materials in the field of optoelectronics.

Impurity states in InSe monolayers doped with group II and IV elements

We have used first-principles calculations to investigate the electronic structures of two-dimensional (2D) InSe monolayers doped with group II and IV elements. The results show that substituting Mg, Ca, Ge, and Sn for indium clearly modifies the electronic and magnetic properties of InSe monolayers and that these substitutions should be easily achieved in a Se-rich environment. Mg- and Ca-doped InSe monolayers develop deep acceptor states and magnetism, whereas substituting Ge and Sn for In induces shallow donor impurity states in these monolayers. Furthermore, the results show that substituting Sn for In provides effective n-type carriers in the InSe monolayer because of the low formation energy and transition level (∼61.10u2009meV). These results should be helpful for related experimental studies.