Michael F. Crommie, Professor

Closed (1) Fabrication and local probe characterization of hybrid molecule/graphene transistor

Applications for fall 2021 are now closed for this project.

The electrical conductance of 2D materials strongly depends on the presence of atomic defects and so understanding how defects scatter electrons is crucial for engineering the properties of 2D devices. Up to now, most studies of the influence of defects on device behavior have focused solely on transport measurements where all of the various defects are globally averaged and information on local nanoscale phenomena is lost. In such measurements, defects are randomly arranged and the effects of any particular defect geometry are averaged out. As devices become smaller, however, the effects of averaging are reduced and the specific arrangements of defects becomes more important. This project aims to fabricate and characterize graphene devices made from the bottom-up by evaporating molecules or atoms as defect structures rather than from the top down using photolithography. This approach enables a higher degree of atomic-scale control over the device structure. We propose to explore how electrically-active adsorbates affect the transport properties of 2D devices. We will focus on measuring how molecules with known chemical and electronic structure effect graphene device electrical conductivity. Application of a gate voltage will be used to tune individual defect electronic structure and to align adsorbate energy levels with the device Fermi energy. This will enable us to probe the effects of resonant defect scattering on the device behavior, as well as the effects of defect hybridization with extended graphene states. We will use scanning probe techniques to study the nanoscale electronic behavior of the defects at the surface of graphene devices. Clean graphene FET devices will be placed into an ultra-high vacuum chamber where molecules can be cleanly deposited onto the graphene surface through thermal evaporation. Control of defect arrangement will be further refined through application of device source-drain current, gating, and local probe manipulation.


This project will give the undergraduate hands-on experience in nanoscale fabrication of electrical devices as well as local probe characterization techniques. This will involve learning how to create graphene transistors through the use of exfoliation and thin film deposition of electrical contacts. The metal electrodes for the transistor will be aligned through the use of shadow masks followed by electron beam evaporation. The undergraduate will additionally learn how to analyze microscopy data using image processing tools based on the computer language Python.

Day-to-day supervisor for this project: Hsinzon Tsai, Post-Doc

Qualifications: Part of the experiment will be required to be carried out in the lab. Labview, Python experience is desirable but not essential.

Weekly Hours: 12 or more hours

Closed (2) Gate tunable TMDs on graphene device

Applications for fall 2021 are now closed for this project.

Two-dimensional transition metal dichalcogenides(TMDs) exhibit rich electronic and topological properties. By integrating TMDs with a gate tunable graphene device, one can continuously change the carrier density in the TMDs and study its impact on the material's local electronic properties with scanning tunneling microscopy.

This project will give the undergraduate hands-on experience in the nanoscale fabrication of electrical devices as well as various surface characterization techniques. The student will assist the fabricate 2D material heterostructure through crystal alignment and thin film deposition such as chemical vapor deposition and molecular beam epitaxy. Various surface characterization techniques will also be used to examine the material properties, such as Raman spectroscopy and atomic force microscopy. , Post-Doc

Qualifications: Part of the experiment will be required to be carried out in the lab. Labview experience is desirable but not essential.

Weekly Hours: 9-11 hrs