Scattering of surface electrons by isolated steps versus periodic step arrays

J. E. Ortega, J. Lobo-Checa, G. Peschel, S. Schirone, Z. M. Abd El-Fattah, M. Matena, F. Schiller, P. Borghetti, P. Gambardella, and A. Mugarza
Phys. Rev. B 87, 115425 – Published 20 March 2013

Abstract

We investigate the scattering of electrons belonging to Shockley states of (111)-oriented noble metal surfaces using angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). Both ARPES and STM indicate that monatomic steps on a noble metal surface may act either as strongly repulsive or highly transmissive barriers for surface electrons, depending on the coherence of the step lattice, and irrespectively of the average step spacing. By measuring curved crystal surfaces with terrace length ranging from 30 to 180 Å, we show that vicinal surfaces of Au and Ag with periodic step arrays exhibit a remarkable wave function coherence beyond 100 Å step spacings, well beyond the Fermi wavelength limit and independently of the projection of the bulk band gap on the vicinal plane. In contrast, the analysis of transmission resonances investigated by STM shows that a pair of isolated parallel steps defining a 58 Å wide terrace confines and decouples the surface state of the small terrace from that of the (111) surface. We conclude that the formation of laterally confined quantum well states in vicinal surfaces as opposed to propagating superlattice states depends on the loss of coherence driven by imperfection in the superlattice order.

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  • Received 30 January 2013

DOI:https://doi.org/10.1103/PhysRevB.87.115425

©2013 American Physical Society

Authors & Affiliations

J. E. Ortega1,2,3, J. Lobo-Checa2, G. Peschel4,5, S. Schirone4,6, Z. M. Abd El-Fattah3, M. Matena3, F. Schiller2, P. Borghetti3, P. Gambardella4,7, and A. Mugarza4

  • 1Universidad del País Vasco, Departmento Física Aplicada I, E-20018 San Sebastián, Spain
  • 2Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, E-20018 San Sebastián, Spain
  • 3Donostia International Physics Center, Paseo Manuel Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
  • 4Catalan Institute of Nanotechnology (ICN), UAB Campus, E-08193 Bellaterra, Spain
  • 5Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
  • 6Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro, 5, I-00185 Roma, Italy
  • 7Instituciò Catalana de Recerca i Estudis Avancats (ICREA), E-08193 Barcelona, Spain

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Issue

Vol. 87, Iss. 11 — 15 March 2013

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