Fabrication of planar screening probes to study strongly correlated 2D materials such as twisted bi-layer graphene*

The emergence of superconductivity in strongly correlated 2D moiré heterostructures has been at the forefront of solid-state research. One example of such a system is magic-angle twisted bilayer graphene (MATBLG). This structure consists of two stacked layers of graphene twisted at an angle of 1.1°. The established method to study such materials is controlling electron-electron interactions while measuring the resistance in the device of study. This is achieved by using image charges in a nearby conductive plane to screen electron-electron interactions. We are pursuing a new method of electron-electron interaction screening based on using a probe with a planar conductive tip. This tip could scan over different regions of the device to locally screen electron interactions with high throughput and tunability. We present the initial methods used to fabricate a localized screening probe to be used for MATBLG screening measurements. This includes successful planarization of a 10-20µm diameter tungsten tip, successful transfer of graphite onto the end of a tungsten tip, and initial work in mechanical exfoliation and etching of graphite pucks with thickness ranging from 500nm-6000nm.