Enabling 2D materials research using inexpensive and lithography-free Hall bar and field effect transistor devices using micro-grid shadow masks

Field effect transistors and Hall bar transport devices are essential components in electrical studies of novel materials, such van der Waals systems like graphene and transition metal dichalcogenides. However, traditional lithography fabrication methods have two key limitations: they involve polymer films and processes that can alter materials' surface properties, and they require costly equipment, depth of expertise, and time that is often unavailable in smaller research laboratories or institutions. We explore mechanical shadow masks using copper TEM micro-grids, an approach that has been successfully used in van der Waals semiconductor device studies [ACS Appl. Mater. Interfaces 12, 46854 (2020)]. When used for Hall effect studies, shadow masking can enable lithography-free fabrication of surprisingly complex device geometries. We discuss how this approach enables high-precision studies of 2D material devices with a minimum of overhead, as well as related projects suitable for an undergraduate laboratory setting.