I. Introduction
Covalently bonded monolayer MoS2 is a potential channel material for future ultrathin body MOSFET [1]. MoS2 crystals are shown to have n-type, nature mostly in experimentally reported transistors [2]–[6]. However, for the successful realization of CMOS circuitry, high-performance p-channel MoS2 transistor is equally required. It is challenging to find a suitable atom for MoS2 crystal which is competent enough to donate holes and be thermodynamically stable at the same time. Using the first principles analysis, niobium emerged as a possible choice among all the p-type dopants for Mo [7]. A p-channel transistor making use of p-type MoS2 crystals fabricated using chemical vapor transport [8] and chemical vapor deposition [9] is attained successfully. The p-type nanoparticles made of Nb-doped MoS2 are also synthesized [10]. Since the nature of MoS2–metal contacts significantly affects the functioning of transistor, it is of utmost importance to probe into the theoretical insights of the electronic properties of Nb-doped MoS2–metal contact apart from the experiments [8].