Ice-assisted electron-beam lithography for MoS transistors with extremely low-energy electrons.

Ice-assisted electron-beam lithography (iEBL) by patterning ice with a focused electron-beam has emerged as a green nanofabrication technique for building nanostructures on diverse substrates. However, materials like atomically thin molybdenum disulfide (MoS), can be easily damaged by electron irradiation. To ensure the performance of devices based on sensitive materials, it is critical to control electron-beam induced radiolysis in iEBL processes. In this paper, we demonstrate that electron-beam patterning with extremely low-energy electrons followed by a heating process can significantly reduce the damage to substrate materials. A thin film of water ice not only acts as a sacrificial layer for patterning but also becomes a protecting layer for the underlying materials. As a result, MoS field effect transistors with back-gate configuration and ohmic contacts have been successfully fabricated. Moreover, the presence or absence of such a protecting layer can lead to the retention or destruction of the underlying MoS, which provides a flexible method for creating electrical insulation or connection on 2D materials.