Abstract
Energy-dependent apparent step heights of two-dimensional ultrathin Pb islands grown on the Si(111) surface have been investigated by a combination of scanning tunneling microscopy, first-principles density-functional theory, and the particle-in-a-box model calculations. The apparent step height shows the thickness- and energy-dependent oscillatory behaviors, which are directly related to the spilling of electron states into the vacuum exhibiting a quantum size effect. This has been unambiguously proven by extensive first-principles scanning tunneling microscopy and spectroscopy simulations. An electronic contribution to the apparent step height is directly determined. At certain energies it reaches values as high as a half of the atomic contribution. The applicability of the particle-in-a-box model to the spilling of electron states is also discussed.
- Received 2 August 2015
- Revised 4 November 2015
DOI:https://doi.org/10.1103/PhysRevB.93.035437
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