Technical: Doping and carrier scattering are of fundamental importance to materials being considered for electronics and sensor application. The ability to synthesize and fabricate materials of reduced dimensionality has provided new platforms with which established performance limits can be surpassed. When materials are of atomic thickness, as is the case with graphene and carbon nanotubes, they also represent the ultimate limit in terms of sensitivity to the local chemical environment. Hence, while much potential exists, experimentally observed properties can be and often are altered by the environment. This project, supported by the Electronic and Photonic Materials (EPM) Program and Solid State and Materials Chemistry (SSMC) Program, addresses the effects of ambient surrounding and interfaces on the observed properties of low-dimensional carbon (graphene and nanotubes) - to distinguish intrinsic characteristics and to elucidate how extrinsic factors alter them. Studies on interactions with substrates can also lead to systems where the effects of mechanical strain can be explored. Successful implementation of this project is expected to lead to new insights into mechanical distortions and Kohn anomaly effects that lead to static and dynamic band gap opening in graphene and metallic carbon nanotubes.
The project addresses basic research issues in a topical area of materials sciences with high technological relevance. Insights gained on chemical and mechanical effects at the low-dimensional carbon/polymer interfaces will enable emerging areas such as flexible electronics and transparent conductors. Studies on strained crystalline interfaces and mechanical effects may lead to accessible routes to tuning the band structure of both graphene and nanotubes opening up new directions in carbon-based high-performance electronics. The interdisciplinary nature of this project provides educational and training opportunities for both graduate and undergraduate researchers who will become the future leaders at the forefront of science and engineering. The results of this project also provide new concepts and demonstration materials for enriching course curricula at the PI's institution and beyond.
Doping and carrier scattering are of fundamental importance to materials being considered for any electronics application. For example, the ability to control carrier density and type is what has enabled the semiconductor industry. Scattering of charge carriers (electrons and holes) by the motion of the constituent atoms (vibrations or phonons) is an important inherent process that can define the ultimate performance of an electronic material. The ability to synthesize and fabricate materials of reduced dimensionality has provided new platforms with which established performance limits can be surpassed. However, with reduced size and dimensionality comes sensitivity to the surrounding environment that can complicate our interpretations of observed characteristics and therefore understanding of fundamental properties of materials. Atomically thin graphene and carbon nanotubes, which represent the ultimate limit in terms of sensitivity to the local chemical environment, have been studied in this project with special attention to doping/charging and phonon scattering. New insights have been gained with respect to how intentional and unintentional defects and interactions with the substrate affect charging/doping and energy relaxation/heat dissipation in grpahene and carbon nanotubes. These results have in turn led to new means of spatially controlling doping profiles in these materials. In addition, proof-of-concept memory devices that exploit substrate charging and the nanometer dimensions of carbon nanotubes for pushing the size and power-consumption limits have been developed. Insights gained and the ability to spatially modulate doping graphene and carbon nanotubes developed in this project can provide means of engineering charge carrier transport in these materials opening up new directions in carbon-based high-performance electronics as well as optoelectronics. The proof-of-concept resistive random access memory devices based on carbon nanotube crossbar electrodes should help to advance the field of memories with respect to ultrahigh density and low power consumption. The results of this project are also providing new concepts and materials for enriching course curricula related to nanoscience and technology.
