Growth and Interface Physics of Epitaxial Graphene

技术。本项目主要研究外延石墨烯（EG）的生长和界面物理特性。由一层或几层sp2键合碳原子组成的石墨碳薄膜，生长在碳化硅衬底上。利用表面科学方法（包括通过低温扫描隧道显微镜和相关技术进行表征），将开发新的EG在SiC上生长的方法，并研究几种类型界面的物理特性。这些界面与纳米级设备有关，它们涵盖了基础材料科学。例如：EG-SiC接口；衬底通过掺杂石墨烯、潜在地改变石墨烯亚晶格对称性以及界面态的形成，深刻地影响了二维电子系统。类似的考虑也适用于连续的石墨烯薄片，从而产生依赖于层的电子特性。Metal-EG联系人;这种接触将三维费米面与二维费米面结合在一起，在界面上具有独特的波矢量匹配（或不匹配）。界面上的功函数差和电压偏置在金属触点下形成了一个2D的屏蔽电荷“水坑”。EG pn结；从空穴掺杂到电子掺杂的过渡发生在门控输运器件中。在这种独特的一维界面上进行简单的波矢量匹配，可以类比为“负折射率材料”或粒子-反粒子过程。在这样一个界面附近，电子相关的影响是未知的。pn结界面也将出现在高工作功能金属触点（或岛）的周长附近，这些触点局部空穴掺杂EG（自然在SiC上掺杂电子）。其他形式的局部掺杂，如边缘的化学修饰，也有望在EG器件中产生pn结。EG-NPEG肖特基垒；延伸的EG片是半金属，而纳米图案的EG （NPEG）带则表现出约束带隙。从半金属过渡到半导体的物理过程类似于金属-半导体界面上肖特基势垒的形成，但过渡区域是原子连续的。电子能谱可以直接获得EG中π带形成的独特的2DES。该方法利用表面科学显微镜/光谱、拉曼光谱和传统的磁输运来探测这些界面的基本物理特性。非技术。本项目涉及电子/光子材料科学和凝聚态物理相关技术领域的基础研究问题。获得的基本理解有望改善器件性能，并允许设计新的电子元件。该项目将研究与教育相结合，为研究生和本科生提供实验室经验和培训，同时进行前沿研究。将积极寻求招募代表性不足的群体进入物理科学领域。该项目通过参与由教育专业人员设计的项目，将研究与各级教育（K-12，本科，研究生，继续教育）联系起来：通过格鲁吉亚教师工业奖学金（GIFT）计划，初中/高中教师在首席研究员的实验室体验7周/夏季的研究。

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.