Non-monotonic thickness dependence of MoS2-Sb contact resistance driven by bandgap and interlayer transport

Contact resistance at metal-two-dimensional semiconductor interfaces is a major factor limiting the performance of emerging two-dimensional electronic devices. Understanding how material thickness influences contact behavior is therefore essential for device optimization. Here, we systematically investigate the layer-dependent contact resistance of MoS2-Sb interfaces using MoS2 field-effect transistors with different layer numbers. Contact resistance was extracted using the transmission line method and compared for devices fabricated on SiO2 and HfO2 gate dielectrics. The results reveal a pronounced non-monotonic dependence of contact resistance on the MoS2 layer number. As the layer number increases from one to three, the contact resistance decreases and reaches a minimum value of 308 Ω·μm for trilayer MoS2, while further increasing the thickness leads to a rise in resistance. Analysis of the electronic band structure and interlayer transport mechanisms indicates that this behavior originates from the competition between bandgap reduction and increasing interlayer transport resistance. In the few-layer regime, bandgap narrowing lowers the Schottky barrier and reduces contact resistance, whereas in thicker layers the growing interlayer resistance dominates carrier transport. These findings provide important insight into thickness-dependent contact physics in two-dimensional semiconductors and offer practical guidance for optimizing contact engineering and channel thickness in next-generation electronic devices.