Interface Structures,Electronic Properties And Thermal Stability Of Graphene/Si(111)

The thermal,electronic,mechanical,and optical properties of monolayer graphene are excellent,opening the door of two-dimensional(2D)materials.Recently,numerous 2D materials with intriguing characteristics have been discovered.The exploration of applications based on these 2D materials is vitally important.This thesis presents systematic studies on the experimental design,fabrication method,interface structure,electronic properties,and thermal properties of atomically smooth(i.e.,ultra-flat)graphene/Si(111).In Chapter One,the background of ultra-flat graphene/Si(111)is discussed,including the applications of graphene/Si(111)devices,established fabrication methods,theoretical work about the graphene/Si interface,and the flatness analysis of the graphene/substrate.Based on above aspects,the ultra-flat graphene/Si(111)is expected to be experimentally achieved.In Chapter Two,the experimental difficulties and our improved fabrication method are introducted.This method is featured by the following aspects:Firstly,the H-Si(111)surface obtained by wet etching is clean and flat with atomic terraces.Secondly,the H-Si surface is protected from oxidization by fast dry transfer of graphene to minimize the exposure time to air.Thirdly,the annealing of the graphene/H-Si(111)is performed under the ultra-high vacuum environment for a long time.The scanning tunneling microscopy(STM)image of the ultra-flat graphene/Si(111)fabricated using this method is compared with that of the rippled graphene/Si(111)obtained by the conventional way.In Chapter Three,the graphene overlayer largely remains electronically intact from the chemically active Si(111)surface,validated from the energy-dependent electronic transparency,Dirac point observation,and further confirmed by the first-principles calculations,transport measurement,X-ray photoelectron spectroscopy(XPS),and Raman spectroscopy.In Chapter Four,different STM images of graphene/Si(111)with different annealing temperature are exhibited.When the annealing temperature is low,the graphene/H-Si(111)structure still maintains.When the hydyogen are desorbed at higher annealing temperature,the graphene/Si(111)-5×5 moire pattern,graphene/Si(111)-c(2×4),graphene/Si(111)-c(2×8),graphene/Si(111)-2x2,and graphene/Si(111)-(?)×(?)patterns coexist.Microscale patterns of graphene/Si(111)-c(2×4),graphene/Si(111)-c(2×8),graphene/Si(111)-2×2,and graphene/Si(111)(?)×(?)are realized after annealing at higher temperature.The decomposition of graphene is observed when the annealing temperature further exceeds 1100 K.In Chapter Five,the experimental results of this thesis are summaried.Centermeter fabrication of ultra-flat graphene/Si(111),the origin of the special angle between graphene and Si(111),the stable structure of graphene/Si(111)-7x7 moire pattern,and the intercalation of functional metal atoms at the ultra-flat graphene/Si(111)interface are discussed.