Study on Graphene Transfer Techniques for Fabrication of High Performance Nanoelectronic Devices.pdf

1、Chemical vapor deposition (CVD) growth of graphene on copper (Cu substrate is apromising approach for production of large scale monolayer graphene for device application, butneed to transfer from Cu to insulating substra

2、te.In General poly (methyl methacrylate) (PMMA) isused as supporting layer while the Cu film etched away.Recent studies show that removing of PMMA is problematic.Here, in this thesis we have studied the graphene transfer

3、 techniques andrelated issues.It also demonstrated a modified transfer method by using a thin protective layer(Nagative Photoresist) which provides interface between graphene and PMMA.In this way the PMMA is not directly

4、 in contact with graphene surface.While, encapsulated graphene sheet withprotective layer shows high quality, clean graphene surface, with reduced P-doping effect andelimination of most of residual contaminations as comp

5、are to standard transfer method, investigatedusing Optical Microscope, Raman spectroscopy, XPS and Atomic force microscopy.
　　We also studied, two-dimensional graphene-like silicon carbide (2d-SiC) martial, usingdensi

6、ty functional theory, key electronic and optical properties of 2d-SiC nanosheets, in particular ofmono-and bilayer 2d-SiC, are investigated.The properties of these nanosheets are found to behighly dependent on their phys

7、ical thickness and geometric configuration.Multilayer 2d-SiCexhibits an indirect bandgap.On the other hand, we found that monolayer 2d-SiC has a directbandgap (～2.5 eV) that can be tuned through the in-plane strain.It al

8、so shows that the opticalconductivity of multilayer 2d-SiC is sensitive to the interlayer spacing.The results suggest thatunlike graphene, silicene and even multilayer 2d-SiC, monolayer 2d-SiC could be a good candidatefo

9、r optoelectronic devices such as light-emitting diodes utilizing its unique properties.
　　Furthermore, we studied the influence of two types of two-dimensional (2D) insulatingsubstrates, hexagonal boron nitride (h-BN)

10、 and fluorographene (FG) on the graphene's opticalproperties at room temperature.Our work show that both substrates can well preserve grapheneoptical properties from 0.6 eV to 3.5 eV and FG substrate can retain graphene

11、pristine propertiesmuch better than h-BN substrate when photon energy is ＜0.6 eV or ＞3.5 eV.Besides, by analyzingthe Kubo formula, the relaxation time of non-freestanding graphene, which can reflect the substrate-graphen

12、e interaction, is highly dependent on the substrate type and its stacking pattern.The substrateeffect on graphene properties are also studied by examining the electronic properties of double-layerstructures.Our results o

13、n the sensitivity issue that caused by stacking pattern and interlayer distancemay provide a reasonable explanation on the inconsistency of substrate-induced bandgap opening ingraphene/h-BN heterostructures discussed in