Localization, splitting, and mixing of field emission resonances induced by alkali metal clusters on Cu(100)

S. Stepanow, A. Mugarza, G. Ceballos, P. Gambardella, I. Aldazabal, A. G. Borisov, and A. Arnau
Phys. Rev. B 83, 115101 – Published 2 March 2011

Abstract

We report on a joint scanning tunneling microscopy (STM) and theoretical wave packet propagation study of field emission resonances (FER’s) of nanosized alkali metal clusters deposited on a Cu(100) surface. In addition to FER’s of the pristine Cu(100) surface, we observe the appearance of island-induced resonances that are particularly well resolved for STM bias voltage values corresponding to electron energies inside the projected band gap of the substrate. The corresponding dI/dV maps reveal island-induced resonances of different nature. Their electronic densities are localized either inside the alkali cluster or on its boundaries. Our model calculations allow us to explain the experimental results as due to the coexistence and mixing of two kinds of island-induced states. On the one side, since the alkali work function is lower than that of the substrate, the nanosized alkali metal clusters introduce intrinsic localized electronic states pinned to the vacuum level above the cluster. These states can be seen as the FER’s of the complete alkali overlayer quantized by the cluster boundaries. On the other side, the attractive potential well due to the alkali metal cluster leads to two-dimensional (2D) localization of the FER’s of the Cu(100) surface, the corresponding split component of the resonances appearing below the bottom of the parent continuum. Our main conclusions are based on the attractive nature of the alkali ad-island potential. They are of general validity and, therefore, significant to understand electron confinement in 2D.

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  • Received 5 November 2010

DOI:https://doi.org/10.1103/PhysRevB.83.115101

© 2011 American Physical Society

Authors & Affiliations

S. Stepanow1, A. Mugarza1, G. Ceballos1, and P. Gambardella1,2

  • 1Centre d’Investigaciò en Nanociència i Nanotecnologia (ICN-CSIC), UAB Campus, E-08193 Bellaterra, Spain
  • 2Instituciò Catalana de Recerca i Estudis Avancats (ICREA), E-08193 Barcelona, Spain

I. Aldazabal1,2, A. G. Borisov3, and A. Arnau1,2

  • 1Donostia International Physics Center (DIPC), P. de Manuel Lardizabal 4, 20080 San Sebastián/Donostia, Spain
  • 2Dpto. de Física de Materiales and Centro Mixto CSIC-UPV/EHU, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apto. 1072, 20080 San Sebastián/Donostia, Spain
  • 3Institut des Sciences Moléculaires d’Orsay, UMR 8214 CNRS-Université Paris–Sud, Bâtiment 351, Université Paris–Sud, 91405 Orsay Cedex, France

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Issue

Vol. 83, Iss. 11 — 15 March 2011

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