Controllable electronic properties, contact barriers and contact types in a TaSe2/WSe2 metal-semiconductor heterostructure.

Two-dimensional (2D) metallic TaSe2 and semiconducting WSe2 materials have been successfully fabricated in experiments and are considered as promising contact and channel materials, respectively, for the design of next-generation electronic devices. Herein, we design a metal-semiconductor (M-S) heterostructure combining metallic TaSe2 and semiconducting WSe2 materials and investigate the atomic structure, electronic properties and controllable contact types of the combined TaSe2/WSe2 M-S heterostructure using first-principles calculations. Our results reveal that the TaSe2/WSe2 M-S heterostructure can adopt four different stable stacking configurations, all of which exhibit enhanced elastic constants compared to the constituent monolayers. Furthermore, the TaSe2/WSe2 M-S heterostructure exhibits p-type Schottky contact (SC) with Schottky barriers ranging from 0.36 to 0.49 eV, depending on the stacking configurations. The TaSe2/WSe2 M-S heterostructure can be considered as a promising M-S contact for next-generation electronic Schottky devices owing to its small tunneling resistivity of about 2.14 × 10-9 Ω cm2. More interestingly, the TaSe2/WSe2 M-S heterostructure exhibits tunable contact types and contact barriers under the application of an electric field. A negative electric field induces a transition from Schottky contact type to ohmic contact (OC) type. On the other hand, a positive electric field leads to a transformation from p-type SC to n-type SC. Our findings provide valuable insights into the practical applications of the TaSe2/WSe2 M-S heterostructure towards next-generation electronic devices.

Embedding of atoms into the nanopore sites of the C6N6 and C6N8 porous carbon nitride monolayers with tunable electronic properties.

Using first-principles calculations, we study the effect of embedding various atoms into the nanopore sites of both C6N6 and C6N8 monolayers. Our results indicate that the embedded atoms significantly affect the electronic and magnetic properties of C6N6 and C6N8 monolayers and lead to extraordinary and multifarious electronic properties, such as metallic, half-metallic, spin-glass semiconductor and dilute-magnetic semiconductor behaviour. Our results reveal that the H atom concentration dramatically affects the C6N6 monolayer. On increasing the H coverage, the impurity states also increase due to H atoms around the Fermi-level. C6N6 shows metallic character when the H atom concentration reaches 6.25%. Moreover, the effect of charge on the electronic properties of both Cr@C6N6 and C@C6N8 is also studied. Cr@C6N6 is a ferromagnetic metal with a magnetic moment of 2.40 µB, and when 0.2 electrons are added and removed, it remains a ferromagnetic metal with a magnetic moment of 2.57 and 2.77 µB, respectively. Interestingly, one can observe a semi-metal, in which the VBM and CBM in both spin channels touch each other near the Fermi-level. C@C6N8 is a semiconductor with a nontrivial band gap. When 0.2 electrons are removed, it remains metallic, and under excess electronic charge, it exhibits half-metallic behaviour.