Graphene has attracted tremendous attention in recent years since its discovery. The unique low dimensional and high electron mobility characteristics make graphene an ideal platform for both fundamental scientific research and technological application. So far, significant progress and understanding has been achieved on its material properties and potential for application. Nevertheless, there are still many aspects to be explored for this promising material until the realization of its full potential. The unique energy band structure of graphene is an interesting fundamental physical issue to be studied. While on the other hand, the gap-less feature around the Dirac point sets an obstacle for further application in electronic devices. Efforts in understanding the interaction of graphene with external substances or physical/chemical excitation could help to improve our ability in manipulating the properties of graphene.

Local anodic oxidation (LAO) with atomic force microscope is a well-developed nanometer scale manipulation technique. With appropriate bias, Bumps or trenches can be formed on single layer graphene (SLG) flake. The technique has been applied on graphene for fabricating prototype electronic devices such as nanoribbons, cellular graphene, and insulated graphene circuit. We experimentally studied the local oxidation kinetics of CVD SLG supported on thin oxide buffered silicon template. With capacitive coupling through the thin buffered oxide, LAO can be achieved at any location in the transferred SLG sheet. We have found a novel way to locally produce strain in SLG by forming silicon oxide protrusion beneath the SLG surface. We expect it could be utilized as a new tuning knob for local manipulation of graphene properties.

We are currently working on understanding the origin of bump or trench generation by LAO in CVD graphene. By systematic LAO and micro-Raman measurements, we are able to determine the dependence of bump/trench generation on initial defect level in SLG. Besides, we have constructed a “bottom up” approach for local LAO patterning manipulation. Using ion implantation in selectively doping the silicon template, we can create regions with vastly different sensitivity to LAO generated strain under the same LAO bias. Currently we are pursuing to understand the physics of LAO of grapheme and link it to the physics of electro-wetting. We have built up collaborative relationship with fellow researcher in photoluminescence measurement to investigate the confinement induced photoluminescence in LAO patterned confined graphene. Furthermore, in order to manipulate the CVD grown graphene properties, particularly the defect conditions of the CVD product, we have constructed a home built rapid thermal CVD system for the growth of CVD graphene.

Involved lab members: