台北市立阳明高级中学-OpticsonGraphene.ppt
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1、Optics on Graphene,Gate-Variable Optical Transitions in Graphene Feng Wang, Yuanbo Zhang, Chuanshan Tian, Caglar Girit, Alex Zettl, Michael Crommie, and Y. Ron Shen, Science 320, 206 (2008).,Direct Observation of a Widely Tunable Bandgap in Bilayer Graphene Yuanbo Zhang, Tsung-Ta Tang, Caglar Girit1
2、, Zhao Hao, Michael C. Martin, Alex Zettl1, Michael F. Crommie, Y. Ron Shen and Feng Wang (2009),Graphene (A Monolayer of Graphite),2D Hexagonal lattice,Electrically: High mobility at room temperature, Large current carrying capability Mechanically: Large Youngs modulus. Thermally: High thermal cond
3、uctance.,Properties of Graphene,Quantum Hall effect, Barry Phase Ballistic transport, Klein paradox Others,Exotic Behaviors,Quantum Hall Effect,Y. Zhang et al, Nature 438, 201(2005),Optical Studies of Graphene,Optical microscopy contrast; Raman spectroscopy; Landau level spectroscopy.,Crystalline St
4、ructure of Graphite,Graphene,2D Hexagonal lattice,Band Structure of Graphene Monolayer,P.R.Wallace, Phys.Rev.71,622-634(1947),Band Structure of Monolayer Graphere,p-Electron Bands of Graphene Monolayer,Band Structure in Extended BZ,Band Structure near K Points,10 eV,Vertical optical transition,Van H
5、ove Singularity,K,K,Monolayer,Bilayer,Band Structures of Graphene Monolayer and Bilayer near K,EF is adjustable,x,x,Exfoliated Graphene Monolayers and Bilayers,Monolayer,Bilayer,Reflecting microscope images.,K. S. Novoselov et al., Science 306, 666 (2004).,20 m,Raman Spectroscopy of Graphene,A.S.Fer
6、rari, et al, PRL 97, 187401 (2006),(Allowing ID of monolayer and bilayer),Reflection Spectroscopy on Graphene,Experimental Arrangement,Doped Si,Graphene,Gold,290-nm Silica,OPA,Det,Infrared Reflection Spectroscopy to Deduce Absorption Spectrum,Differential reflection spectroscopy: Difference between
7、bare substrate and graphene on substrate,A,B,-dR/R (RA-RB)/RA versus w,RA: bare substrate reflectivity RB: substrate + graphene reflectivity,20 m,dR/R = -Reh(w)s(w),h(w) from substrate s(w) from graphene: interband transitons free carrier absorption,Re s(w)/w: Absorption spectrum,Spectroscopy on Mon
8、olayer Graphene,Monolayer Spectrum,x,C: capacitance,Experimental Arrangement,Doped Si,Graphene,Gold,290-nm Silica,OPA,Det,Vg,Gate Effect on Monolayer Graphene,X,X,X,Small density of states close to Dirac point E = 0 Carrier injection by applying gate voltage can lead to large Fermi energy shift .,EF
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