Precursor Free Growth of MoS₂ Monolayer Devices With Naturally Formed Contacts

Interest in two dimensional Transition Metal Dichalcogenides (TMDs) has remained robust due to properties such as their direct band gap, large exciton binding energies, sizeable spin-orbit couplings, and spin-valley interactions. While there are several techniques for developing TMD based devices, in this work we propose a unique, precursor free, Chemical Vapor Deposition (CVD) method in which the device in grown in situ with naturally formed contacts. A molybdenum metal pattern, which will form an electrical contact with the TMD, is sputtered on to the substrate prior to the growth. The oxide layer that then naturally forms on the metal surface serves as the precursor for the subsequent growth. In contrast to completely sulfurizing an ultrathin Mo layer, the TMD material grows on, and away from, the thick molybdenum patterns across the Si substrate. Photoluminescence and Raman studies show that the growth can be tuned to produce monolayer and bi-layer Molybdenum Disulfide (MoS₂). We also study the self-limiting nature of the growth process and compare it to the growths with the MoO₃ precursor.