石墨烯光學(xué)介紹ppt課件(編輯修改稿)
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【文章內(nèi)容簡(jiǎn)介】 (w) from substrate s(w) from graphene: interband transitons free carrier absorption Re s(w)/w: Absorption spectrum Spectroscopy on Monolayer Graphene Monolayer Spectrum x dR/R Ew ?2EF 22000 e l e c t r ons/ hol e s = ( ) / ( v )v | |( ) p dop e d: 0 c a n be a djus t e d by c a r r i e r i nje c t i on th r oug h .FEFFFFgFgnE dE EEnn C V V VEV???????????? ? ??2( ) 2 / FE E v???C: capacitance Experimental Arrangement Doped Si Graphene Gold 290nm Silica OPA Det Vg Gate Effect on Monolayer Graphene 2( ) 2 / v FEE???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 can be shifted by ~ eV with Vg ~ 50 v。 Shifting threshold of transitions by ~1 eV dR/R w2EF If Vg = Vg0 + Vmod, then should be a maximum at mod( / )RRVd?? 2 FEw ?Vary Optical Transitions by Gating Laser beam Vary gate voltage Vg. Measure modulated reflectivity due to Vmod at V ( Analogous to dI/dV measurement in transport) 0( / )VRRVd????????Results in Graphene Monolayer w = 350 meV 2 FEw ? 0220v | |( ) = ( v ) | |FFgF F gEnn C V VE C V V?????????The maximum determines Vg for the given EF. Mapping Band Structure near
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