Professor Masahiro Ishigami

Department of Physics and Nanoscience Technology Center, University of
Central Florida

Revealing the dominant scatterer in Graphene on SiO₂

Abstract:

Graphene, a single layer of graphite, is a unique material with exotic electronic properties. A hexagonal two-dimensional network of carbon atoms composes graphene; it is exactly one atom in thickness, and every carbon atom is a surface atom. Defects, adsorbates, substrate-induced structural distortion and charge disorder can affect the transport property of graphene and, therefore, can obscure its intrinsic property. Among these extrinsic factors, defects and adsorbates can be controlled effectively. However, the impact of the substrate-induced disorder, which can reduce the carrier mobility of graphene by more than three orders of magnitude, cannot be controlled and remains poorly understood.

Thermally grown silicon oxide (SiO₂) is currently the most commonly used substrate for graphene. We have measured the impact of atomic hydrogen adsorption on the electronic transport properties of graphene sheets on SiO₂ substrates as a function of hydrogen coverage and initial, pre-hydrogenation field-effect mobility in ultra high vacuum. The saturation coverages for different devices are found to be proportional to their initial mobility, indicating that the number of native scatterers is proportional to the saturation coverage of hydrogen. By extrapolating this proportionality, we show that the field-effect mobility can reach 1.5×104 cm2 /V s in the absence of the hydrogen-adsorbing sites. The affinity to hydrogen is the signature of the most dominant type of native scatterers in graphene-based field-effect transistors on SiO₂. Our identification of the native scatterer in graphene on SiO₂ will enable further exploitation of graphene in both applied and fundamental sciences.