中文摘要：

在分子束外延（MBE）设备中,采用高温退火的方法在6H-SiC（0001）表面外延石墨烯,并研究了退火时间对外延石墨烯形貌和结构的影响.利用反射式高能电子衍射（RHEED）、原子力显微镜（AFM）、激光拉曼光谱（Raman）和近边X射线吸收精细结构（NEXAFS）等实验技术对制备的样品进行了表征.RHEED结果发现,不同退火时间的样品在SiC衍射条纹的外侧都出现了石墨烯的衍射条纹.AFM测试表明,外延石墨烯的厚度随退火时间增加而增大,且样品孔洞减少、表面更加平整.Raman测试表明,外延石墨烯拉曼谱中2D峰和G峰的位置相对高定向热解石墨（HOPG）中2D峰和G峰的位置蓝移,且退火时间增加,峰的蓝移量减小.对样品中碳原子K边NEXAFS谱测量显示,样品中存在sp2杂化的碳原子,退火时间增加使碳原子的1s→π以及1s→σ吸收的强度增大,且1s电子到π态的吸收峰相对HOPG的向高能偏移.

英文摘要：

Epitaxial graphene layers were successfully grown onto Si-terminated 6H-SiC（0001） substrates by thermal annealing using an ultrahigh vacuum molecular beam epitaxy（MBE） chamber.The morphology and structure of the samples annealed for different time were characterized by reflection high energy diffraction（RHEED）,Raman spectro-scopy,atomic force microscopy（AFM） and near edge X-ray absorption fine structure spectroscopy（NEXAFS）.The graphene diffraction steaks were found in the RHEED patterns for all samples.AFM results showed that as the annealing time increased,the thickness of the graphene layers increased and the surface morphology appeared smoother with the out-of-order voids reduced.Raman results showed that the G peak and the 2D peak of graphene were obviously blue-shifted compared to those of highly-oriented pyrolytic graphite（HOPG）.At longer annealing time,the amount of blue-shift decreased.C K-edge NEXAFS results revealed that the intensity of the resonance absorption peaks for 1s→π and 1s→σ for the sp2 hybridized C atoms increased when the samples were annealed over longer periods.The 1s→π peaks of these samples were at higher energies compared to those of HOPG.