Thermal decomposition of SiC at high temperature usually brings about excessively fast Si sublimation and a very rough surface. In order to fabricate high-quality homogeneous epitaxial graphene on a SiC(0001) substrate, highly reactive erbium atoms are employed in this work. Scanning tunneling microscopy and Raman spectroscopy have been utilized to investigate the modulations of Er atoms on graphitization evolution and structural defects for graphene after annealing durations. Experimental results show that Er atoms pre-deposited on clean substrates can definitely enhance the surface graphitization of SiC and make graphene grow in a controllable way. The existence of Er layer is believed to break Si–C bonds at low temperature and to decrease the Si sublimate rate. It is also demonstrated that Er atoms can modify the type of structural defects in graphene, and the areal density of flower defects increases to 1.22 × 1012 cm−2, quadrupling that in pristine graphene. This work puts forward a fabrication method for epitaxial graphene with flower defects in high density and will enlighten some future applications of graphene in nanoelectronics, electron energy filtering, and chemical catalysis.
Surface morphological features and nanostructures generated during SiC graphitization process can significantly affect the fabrication of high-quality epitaxial graphene on semiconductor substrate. In this work, the surface morphologies and atomic structures during graphitization process of 4H-SiC (0001) have been studied by using scanning tunneling microscopy. Our high-magnified STM images exhibit the appearance and gradual developments of SiC (1×1) nanostructures after 1100 °C cleaning treatments, irregularly distributed among carbon nanocaps and (√3×√3) reconstruction domains. A model for the formation and growth progression of SiC (1×1) nanostructures has been proposed. When post-annealing temperature reaches 1300 °C, the nano-holes and nano-islands can be observed on the surface and multilayer graphene is often detected lying on the top surface of those nano-islands. These results provide profound insights into the complex evolution process of surface morphology during SiC thermal decomposition and will shed light on the fabrication of SiC nanostructures and graphene nanoflakes.
Intercalation of atomic species is a practicable method for epitaxial graphene to adjust the electronic band structure and to tune the coupling between graphene and SiC substrate. In this work, atomically flat epitaxial graphene have been prepared on 4H-SiC(0001) using flash heating method in an ultrahigh vacuum system. Scanning tunneling microscopy, Raman spectroscopy and electrical transport measurements are utilized to investigate surface morphological structures and transport properties of pristine and Er-intercalated epitaxial graphene. It is found that Er atoms are intercalated underneath graphene layer after annealing at 900℃, and the intercalation site of Er atoms is located mainly at the buffer-layer/monolayer-graphene interface in monolayer domains. We also report the different behaviors of Er intercalation in monolayer and bilayer region, and the experimental results show that the diffusion barrier for Er intercalated atoms in the buffer-layer /monolayer interface is at least 0.2 eV higher than that in the first/second graphene-layer interface. The appearance of Er atoms is found to have distinct impacts on the electronic transports of epitaxial graphene on SiC(0001).
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