Electrical Transport of High-Quality CVD-Grown MoSe₂Nanoribbons

Two-dimensional (2D) materials such as transition metal dichalcogenides are excellent candidates for creating novel nano-electronic and photonic devices. Previous research indicates that the edge states of MoS₂ could strongly influence its conductivity, and the 2D honeycomb structure enables different electronic performance along the zigzag and armchair edges. Understanding and controlling the conductivity is essential in devices like field effect transistors that use MoS₂ as the channel. To date, transport along edge states of MoSe₂ nanoribbons, which have substantially reduced dimensionality relative to 2D crystals, has not been explored. In this project, we used chemical vapor deposition (CVD) to synthesize MoSe₂ nanoribbons through directed growth on phosphine (PH₃)-treated Si substrates. This approach yields directed growth of monolayer MoSe₂ to form narrow (< 1μm) nanoribbons. Tip-enhanced photoluminescence (TEPL) maps reveal a significant difference between the emission intensity at the edges and center of the nanoribbon. Different metals (Ti, Au) were grown on MoSe₂ monolayer flakes to discover the contact metal that gives the best device performance. We then used the chosen metal and e-beam lithography to pattern contacts on the nanoribbons in a Hall bar configuration with the side contacts at the edges and tips of the nanoribbons. The influence of edge states on the electrical performance of MoSe₂ nanoribbons was investigated by conductivity and Hall transport measurements. Current flow in the transverse and longitudinal directions of the nanoribbon was compared to analyze the importance of edge states on MoSe₂ nanoribbon conductivity.