Growth and Interface Physics of Epitaxial Graphene

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Technical. This project focuses on the growth and investigates the interface physics of epitaxial graphene (EG)?thin graphitic carbon films with one or a few sheets of sp2-bonded carbon at-oms, grown on silicon carbide substrates. Using surface science methods (including characteriza-tion via low-temperature scanning tunneling microscopy and related techniques), new growth methods for EG on SiC will be developed, and the physics of several types interfaces will be studied. These interfaces are relevant for nanometer-scale devices, and they encompass funda-mental materials science. For example: EG-SiC interface; the substrate profoundly affects the 2D electron system by doping the graphene, by potentially changing the graphene sublattice symme-try, and by the formation of interface states. Similar considerations hold for successive graphene sheets, resulting in layer-dependent electronic properties. Metal-EG contacts; this contact mates a 3D Fermi surface to a 2D Fermi surface, with unique wave vector matching (or mismatching) across the interface. The work function difference and voltage bias across the interface create a 2D 'puddle' of screening charge under the metal contact. EG pn junctions; transitions from hole-doping to electron-doping occur in gated transport devices. Simple wave-vector matching across such a unique 1D interface brings analogies to 'negative index materials' or particle-antiparticle processes. The effect of electron correlations near such an interface is unknown. pn junction in-terfaces also will be present near the perimeter of high-work-function metal contacts (or islands) that locally hole-dope the EG (which is naturally electron-doped on SiC). Other forms of local-ized doping, such as chemical modification of edges, are also expected to create pn junctions in EG devices. EG-NPEG Schottky barriers; extended EG sheets are semi-metals, whereas nano-patterned EG (NPEG) ribbons exhibit a confinement band gap. The physics of the transition from semi-metal to semiconductor is similar to that of Schottky barrier formation at a metal-semiconductor interface, but the transition region is atomically continuous. The unique 2DES formed by the pi-bands in EG is directly accessible to electron spectroscopies. The approach util-izes surface science microscopies/spectroscopies, Raman spectroscopy, and conventional magnetotransport to probe the basic physics of these interfaces. Non-Technical. The project addresses fundamental research issues in a topical area of elec-tronic/photonic materials science and condensed matter physics having technological relevance. Basic understanding gained is expected to lead to improved device performance, and to allow de-sign of new electronic components. The project integrates research and education providing graduate and undergraduate students with laboratory experience and training while conducting forefront research. Recruitment of underrepresented groups into the physical sciences will be ac-tively pursued. The project ties research to education at all levels (K-12, undergraduate, graduate, continuing-ed), through participation in programs designed by education professionals: Middle/High school teachers experience research in the principal investigator's laboratory for 7 weeks/summer through the Georgia Industrial Fellowships for Teachers (GIFT) program.