Image potential states in monolayer, bilayer, and trilayer epitaxial graphene studied with time- and angle-resolved two-photon photoemission spectroscopy
2014; American Physical Society; Volume: 89; Issue: 15 Linguagem: Inglês
10.1103/physrevb.89.155303
ISSN1550-235X
AutoresKazutoshi Takahashi, Masaki Imamura, Isamu Yamamoto, Junpei Azuma, Masao Kamada,
Tópico(s)Quantum and electron transport phenomena
ResumoImage potential states (IPSs) on monolayer, bilayer, and trilayer graphene epitaxially grown on SiC(0001) have been studied by time- and angle-resolved two-photon photoemission (2PPE) spectroscopy. The free-electron-like dispersions of even and odd symmetry IPSs with a quantum number of $n$ = 1${}^{+}$, 1${}^{\ensuremath{-}}$, 2, 3 were observed. All observed IPSs showed the dispersions with effective masses of ${m}^{*}=1.0\ifmmode\pm\else\textpm\fi{}0.1{m}_{e}$. The 2PPE intensity of the lowest IPS ($n$ = 1${}^{+}$) was attenuated with an increasing number of graphene layers. The time-resolved 2PPE measurements revealed that these IPSs have significantly shorter lifetimes, suggesting a coupling of IPSs with electronic states in the buffer layer and the SiC substrate.
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