Superatom orbitals of C${}_{60}$ on Ag(111): Two-photon photoemission and scanning tunneling spectroscopy

Superatom orbitals of C $_{60}$ on Ag(111): Two-photon photoemission and scanning tunneling spectroscopy

G. J. Dutton, D. B. Dougherty, W. Jin, J. E. Reutt-Robey, and S. W. Robey

Phys. Rev. B 84, 195435 – Published 8 November 2011

Abstract

The unoccupied electronic structure of C $_{60}$ layers on Ag(111) was investigated with two-photon photoemission (2PPE) and scanning tunneling spectroscopy (STS). The focus, in addition to providing unoccupied level assignments for C $_{60}$ monolayers, is on identifying signatures of C $_{60}$ superatom molecular orbitals (SAMOs), diffuse unoccupied levels weakly bound by the spherical potential of the fullerene shell, in the two complementary techniques. The s-SAMO is identified 3.3 eV above the Fermi level in 2PPE and at a bias of 3.5 eV in STS. Possible contributions from $p$ -SAMO levels are also discussed for both measurement techniques. The results are compared with recent low-temperature scanning tunneling microscopy (LT-STM) work that investigated C $_{60}$ SAMOs on Cu(111) and oxygen-covered Cu(110) surfaces and with previous 2PPE measurements for C $_{60}$ monolayers on Au(111) and Cu(111).

Received 18 April 2011

DOI:https://doi.org/10.1103/PhysRevB.84.195435

Authors & Affiliations

G. J. Dutton¹, D. B. Dougherty², W. Jin³, J. E. Reutt-Robey⁴, and S. W. Robey^1,*

¹National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
²Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
³Department of Chemistry and Biochemistry, University of California–San Diego, La Jolla, CA 92093, USA
⁴Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA

^*steven.robey@nist.gov

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Vol. 84, Iss. 19 — 15 November 2011

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