The influence of the electrode crystallinity and channel layer numbers to the contact resistance of molybdenum disulfide transistors

With the assist of van der Waals epitaxy, copper electrodes with enhanced crystallinity are fabricated on molybdenum disulfide (MoS₂) surfaces. Through the sequential mono-layer MoS₂ transferring procedures, bi-layer MoS₂ transistors are fabricated. Compared with the device with mono-layer MoS₂, over two orders of magnitude enhancement in drain currents are observed for the bi-layer MoS₂ transistor. The field-effect mobility values are therefore increased from 2.86×10⁻³ (mono-layer MoS₂) to 0.94cm²·V^-1·s^-1. The results demonstrate that except for the work function matching, the crystallinity of the contact electrode plays a more important role in reducing the contact resistance at the metal electrode and the 2D material channel interface. By using the mono-layer MoS₂ layer to separate the mono-layer MoS₂ channel to the dielectric layer, much enhanced device performances can be observed for bi-layer MoS₂ transistors.