Anisotropic charge transport at the metallic edge contact of ReS2 field effect transistors

The in-plane anisotropy of electrical conductance in two-dimensional materials has garnered significant attention due to its potential in emerging device applications, offering an additional dimension to control carrier transport in 2D devices. However, previous research has primarily focused on the anisotropy within electrical channel, neglecting the significant impact of anisotropic electrical contacts of 2D materials. Here, we investigate anisotropic charge transport at the metal contacts of hBN-encapsulated ReS 2 using edge-contacted Field Effect Transistors. We observed the marked difference in contact resistance between the cross-b and b directions, suggesting that charge transport from the metal to ReS 2 is more efficient along the b direction. This difference in efficiency results in a substantial contact anisotropy, reaching ~70 at 77 K. Our findings indicate that the measured Schottky Barrier Height along the b direction is ~35 meV, which is smaller than along the cross-b direction. Moreover, the tunneling probability along the b direction is two times larger than along the cross-b direction. Our results indicate that both Schottky Barrier Height and tunneling amplitude are the primary contributors to the high contact anisotropy of ReS 2 . This work provides a valuable guideline for understanding how in-plane orientation influences charge transport at metallic contacts in 2D devices. In-plane anisotropy of electrical conductance in 2D materials is an important element in engineering 2D devices. Here, the charge transport anisotropy at the metal contacts of hBN-encapsulated ReS 2 field-effect transistors is investigated, revealing a substantial contact anisotropy ratio of up to 70 at 77 K.