Variability in synthetic MoS₂ devices: Effect of the growth substrate

Implementing a realistic electronic system from transition metal dichalcogenides (TMDs) relies on the ability to produce high-performance devices with homogenous properties. Continuing progress on large-area growth techniques, e.g. chemical vapor deposition (CVD) has improved the optical and electrical properties of monolayer TMDs, including MoS₂. However, reducing device-to-device variations remains a challenge [1]-[2], spurring new investigations to understand the physical origins of this problem in TMD devices. Here, we show that the strong coupling between the as-grown monolayer MoS₂ and the SiO₂ growth substrate causes (1) significant inhomogeneity in the electrical properties of the transistors and (2) significant degradation of the device metrics including carrier mobility and contact resistance. By reducing the binding energy, and thus increasing the van der Waals gap, between the MoS₂ and the original growth substrate using our new gold-assisted layer transfer, we observe remarkable improvements in key device metrics (~7× in mobility and ~100× in contact resistance) and device variability (~10×).