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The Study On The Fabrication And Characterization Of Graphene Grown On SiC Substrates

Posted on:2013-04-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:D C WangFull Text:PDF
GTID:1228330395455447Subject:Microelectronics and Solid State Electronics
Abstract/Summary:PDF Full Text Request
As a flat planar material existed stably and independently at room temperature, graphene is a two-dimensional (2D) honeycomb lattice of sp2-hybridization carbon atoms, also a basic block and mother material of other carbon-based materials such as graphite, carbon nanotubes and Fullerenes and so on. The special lattice structure gives graphene the extraordinary physical, chemical, mechanical, electrical, thermal and optical properties, so graphene may be regarded as one of the promising candidates, aiming at breaking the physical limit effect in Si technology, extending Moore’s law in the post-CMOS era. Therefore, how to prepare high-quality, large-area and low defect graphene is an urgent issue. Among the preparation methods, epitaxial graphene grown on single-crystalline silicon carbide (SiC) has been paid a high expectation in graphene-based electrical devices due to its compatibility with the current semiconductor technology. However, there still exist many factors to effect the formation of graphene, such as the type of substrate, Si-face or C-face, the conditions (UHV and argon pressure), growing temperature and time. At present, the formation mechanism of epitaxial graphene has not yet fully understood.In this dissertation the formation mechanism of epitaxial graphene grown on SiC substrates is studied in theory and experiment. Especially the process method and characterization technology of epitaxial graphene are investigated, and the main contributions are as follows:(1) The preparation of SiC subatrates used to grow high quality epitaxial graphene with hydrogen-etching process has been studied. Based on the pre-cleaning substrate, the hydrogen-etching process has been used to deal with the Si-face (0001) and C-face (0001)4H/6H-SiC substrates in order to remove the chemical mechanical scratches on as-received substrates and form a regular atomic stepped surface with the steps high several nanometers and terraces width microns. This morphography helps epitaxial graphene nuclearation and grow larger on the SiC subatrates.(2) The effects of different growth temperature on the formation of epitaxial graphene have been studied. Using the growth kinetics, nuclearation theory and Raman spectroscopy, we have analyzed how the growth temperature affecting on the formation of epitaxial graphene grown on Si-or C-face SiC substrates under an appropriate pressure conditions. It shows that a higher growth temperature can help the formation of better quality epitaxial graphene samples and also can decrease the influence of the substrates and impurities. Moreover, the stacking types and the thickness of epitaxial graphene grown on Si-or C-face SiC substrates are compared.(3) By analyzing the advantage and disadvantage of epitaxial graphene grown under ultra-high vacuum and atmospheric argon pressure conditions, a new approach has been proposed, which grows epitaxial graphene under lower-pressure argon condition and explores a full process routes to achieve centimeters order of magnitude of epitaxial graphene on Si-face of4H-SiC (0001) substrates at a pressure of4mbar. The measurement results demonstrate that the quality of epitaxial graphene is very similar to the current reported results in this field.This dissertation is composed of six chapters as follows:Chapter Ⅰ is Introduction to make a brief introduction of lattice structure, the basic properties, the current research progress of graphene, and the formation mechanism of four main preparation methods (Micro-mechanical exfoliation of graphite, Chemical Vapor Deposition on metal substrate, the reduction of graphite oxide and epitaxial graphene grown on SiC substrates) and their advantages and disadvantages.In Chapter Ⅱ, the growth mechanism and characterization methods of epitaxial graphene are presented. It describes the physical nature of SiC single crystallines, the main growth process of epitaxial graphene (hydrogen-etching, removing oxides and epitaxial growth process), and the characterization techniques such as the confirmation, size, morphology and the thickness of epitaxial graphene.In Chapter Ⅲ, the investigation of the hydrogen-etching process is presented. Based on pre-cleaning SiC substrates, different hydrogen-etching routes have been implemented on Si-and C-face4H/6H-SiC substrates. Using atomic force microscope, it is confirmed that Si-and C-face of SiC substrates have different hydrogen etching process.In Chapter Ⅳ, the influence of growth temperatures on the formation of epitaxial graphene is analyzed. Under an appropriate pressure, by changing the growth temperatures (from1200to1500℃) for4H-SiC (0001) Si-face substrates, and by changing the growth temperatures (from1400to1600℃) for6H-SiC(0001) C-face substrates, the size and the quality of epitaxial graphene have been studied. Especially, the non-AB stacking type epitaxial graphene grown on the C-face substrates has been characterized using Raman spectroscopy in order to investigate its formation mechanism.In Chapter Ⅴ, the growth of large-area epitaxial graphene is studied. At a lower pressure (4mbar), on the Si-face4H-SiC substrate, epitaxial graphene with size of centimeters order of magnitude has been successfully grown and then the characterizations, such as its size, thickness, morphological structure and chemical compositions of carbon atoms on the interface of epitaxial graphene and SiC substrates, have been achieved using scanning electron microscopy, atom force microscopy, Raman spectroscopy and X-ray Photoelectron Spectroscopy.Chapter VI is the conclusion for this dissertation and gives some suggestions for the further research.
Keywords/Search Tags:Graphene, Epitaxial Graphene, SiC substrate, Raman spectroscopy
PDF Full Text Request
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