Chemical doping of transition metal dichalcogenides (TMDCs) based field effect transistors: A review

Transition metal dichalcogenides (TMDCs), the two dimensional layered structures with significant band gap have been considered as noteworthy candidates for advanced electronic applications. Here we review various chemical dopants in TMDC materials that modulate charge carrier concentrations and hence influence other electrical attributes. It is reported that different features of TMDCs based devices such as mobility, channel and contact resistances and on/off current ratio have been significantly upgraded. Chemicals such as LiF, Benzyl viologen, P-toluene sulfonic acid, Chloride molecules, Potassium (K) and Hydrazine are reported to induce n-type doping in TMDC materials while AuCl3, chemical sulfur treatment (ST) utilizing ammonium sulfide [(NH4)(2)S] and Octadecyltrichlorosilane are reported as p-type dopants. The oxide Al2O3 acts as p-type and Amorphous Titanium Suboxide (ATO) acts n-type dopant. The literature reviewed here, reports that p-type doping improves the device stability thereby minimizing the hysteresis effect, while n-type doping improves the mobility of the samples. It also reviewed the temperature-dependent in situ calculations performed via DFT, these results showed that conduction because of n-type carriers is intrinsic property that is indorsed to defects (tellurium vacancies) in TMDCs. This review presents the comprehensive summary of the role of dopants to modulate the numerous electronic transport, electronic and optical properties of TMDCs based field-effect transistors and provide future insights towards state of the art nanoelectronic devices.