Title:

Tuning Charged Impurity Scattering in Graphene with Nanoparticles

Speaker:

Dr. Jing Shi

Affiliation:

Professor of Physics at University of California - Riverside

When:

Tuesday, October 5, 2010 at 3:00:00 PM   Add to Calendar

Where:

MiRC Building, Room 102 A&B

Host:

Gina Adams
gina.adams@chbe.gatech.edu

Abstract

Charged impurity scattering is believed to be a main source limiting the carrier mobility in unsuspended graphene. In our recent work, we introduce nanoparticles (e.g. Fe3O4, CdSe, or TiO2) wrapped with molecules as a layer of charge reservoir above the graphene sheet. We obtain very large tunability in both carrier mobility and the charge neutral point of graphene by manipulating its charge environment. Low temperature mobility ranging from 3,000 to 19,000 cm^2V^-1s^-1 can be reversibly tuned by controlling the charge state in nanoparticles and graphene. The results support the charged impurity scattering model. In graphene devices with a wide range of mobility, we have studied the electrical and thermoelectric transport properties in both classical and quantum Hall regimes. We have found that although the Mott relation holds very well at all densities for relatively low mobility samples, it fails at low densities for high mobility samples. This indicates that the charged impurities induces significant carrier density fluctuations in low mobility samples that prevents us from accessing the low density region. I will lso discuss a much enhanced Nernst effect near the Dirac point in high mobility samples.

Biography

Biography is not available at this time.