Post-Grant Reports


Contact Barriers and Doping in 2D Field Effect Transistors

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Condensed Matter Physics | Physics


A new class of materials, known as 2D materials, and the devices made from them, have become one of the hottest areas of physics research. The device performance is commonly characterized using macroscopic current-voltage measurements, however, the factors limiting performance are microscopic in nature—including contact barriers, uniformity of electrostatic doping, contamination, and small defects like holes and tears in the 2D sheet. This project employed our state-of-the art Asylum Cypher Atomic Force Microscope to image both the topography of films and devices, and to map their electronic response.

This project focused on characterization of the electronic response in both AM and FM Kelvin Probe Force Microscopy (AM-KPFM and FM-KPFM), as well as in conductance microscopy, so that these techniques can be applied to studying 2D devices. We explored a number of procedural steps, cantilevers, probe tips, and techniques, to improve the repeatability and the quantitative nature of the signal response. Although the microscope is capable of FM-KPFM, this mode was not incorporated into the software, and so code and procedures were developed. Results show a linear correlation between AM-KPFM signal and applied bias to the 2D device. This is also true for FM-KPFM signals. These results will allow for better microscopic characterization of electronic materials, including 2D materials and devices.


This research was conducted as part of a Linfield University Student-Faculty Collaborative Research Grant in 2020, funded by the Office of Academic Affairs.

Student collaborators were Joseph Murphy and Rebekah Smith.