Controllable p-type doping of monolayer MoS2 with tantalum by one-step chemical vapor deposition

Abstract

Molybdenum disulfide (MoS₂) is natively an n-type semiconductor due to omnipresent electron-donating sulfur vacancies, indicating that the synthesis of high-quality p-type semiconducting MoS₂ has been challenging. Substitutional doping has been proved to be an effective and stable approach to manipulate the electronic properties of two-dimensional (2D) transition metal dichalcogenides (TMDs). Group five transition metals such as vanadium (V), niobium (Nb), and tantalum (Ta) are potential alternative p-type dopants. In particular, Ta has more intriguing properties than V and Nb, resulting in exceptional performance in many applications. Herein, we have predicted the p-type doping effect of Ta-doped MoS₂ with the Fermi-level shifting to the valence band maximum based on density functional theory. The large-area monolayer p-type Ta-doped MoS₂ with different doping concentrations has been synthesized via a simple one-step NaCl-assisted CVD method. The energy-dispersive X-ray spectroscopy (EDS) characterization indicated that the highest Ta doping concentration can be up to 1.28% atomic percent by controlling the proportion of Ta with respect to the Mo precursor. The room-temperature and temperature-dependent electrical measurements of Ta-doped MoS₂ transition-effect-transistors (FETs) all show an ambipolar behavior and present an n- to p-type conversion with increasing Ta doping concentrations. The successful synthesis of p-type Ta-doped MoS₂ in this study offers opportunities for advanced technologies and fundamental studies and provides significant potential for future electronic and optoelectronic applications of 2D materials.