Nickel diffusion into MoS2 and the effect of annealing on contact resistance

Abstract

Metal-semiconductor interfaces are crucial for the performance of many devices and understanding interactions between material interfaces after processing is therefore of interest. Here, field-effect transistors with Ni contacts are studied to determine the effects of annealing on contact resistance. Contact resistance and total resistance of as-deposited and annealed field-effect transistors with Ni/Ti/Au contacts increase upon annealing, with higher annealing temperatures yielding a greater increase in contact resistance. It appears that Ni diffusion into MoS2 correlates with the observed higher contact resistance, and transmission electron microscopy, energy dispersive spectroscopy, and electron energy loss spectroscopy reveal the presence of Ni in single crystal MoS2 flakes after annealing Ni/MoS2 in ultra-high purity Ar gas at 400 °C. Metal diffusion into 2D semiconductors like MoS2 may help or hurt device performance, and this work highlights the importance of considering the effects metal diffusion may have on contact resistance.