Metal-semiconductor junctions, electrical junctions in which a metal is linked to a semiconducting material, are crucial components for numerous electronic and optoelectronic devices. While they are now widely produced and used worldwide, creating good quality junctions that integrate conventional metals and 2D semiconductors can be difficult.
Illustration and optical images of the graphene-assisted metal transfer printing process. a, Schematic of the graphene-assisted metal transfer printing process for both weakly and strongly adhering metals: six different metals deposited on wafer-scale Gr/Ge substrate. b, Photographs corresponding to Au patterns transferred onto a four-inch SiO2 wafer. The inset shows an optical image of the transferred Au pattern array. Credit: Liu et al. In fact, when applied to 2D materials, conventional metal deposition techniques, which entail a process known as ion bombardment, can cause a chemical disorder. In addition, existing transfer printing techniques, which involve the pre-deposition and transfer of metal electrodes on the surface of 2D materials, have been found to perform poorly due to the creation of chemical bonds on the substrate for the pre-deposition that hinder the electrodes' transfer. Researchers at the Chinese Academy of Sciences, Hunan University, City University of Hong Kong and Fudan University have recently developed a new technique that could be used to transfer metal electrodes on 2D materials more effectively, enabling the development of more reliable metal-semiconductor junctions. This technique, introduced in a paper published in Nature Electronics, entails the delamination of metal electrode arrays from a graphene wafer, and their subsequent transfer printing onto different 2D materials. "For the first time, in 2013, we reported that continuous graphene monolayers can be grown via CVD directly on semiconducting Ge(001) surfaces, making a significant departure from conventional metallic systems," Zengfeng Di, one of the researchers who carried out the study, told TechXplore. "Because of the insulating property of intrinsic Ge at the temperature below 10K, we carried out the research on graphene-mediated superconductivity in the metal nano-islands/graphene hybrid on Ge substrate, without the transfer of…