High resolution scanning tunneling spectroscopy of ultrathin Pb on Si(111)-(6x6) substrate

TL;DR

This study uses high-resolution scanning tunneling spectroscopy to investigate the electronic properties of ultrathin Pb layers on a Si(111)-(6x6)Au surface, revealing quantized states in nanometer-scale islands and theoretical insights into tip effects.

Contribution

It provides new experimental data on quantized electronic states in ultrathin Pb islands and introduces a theoretical model to interpret STM measurements considering tip variations.

Findings

Detection of quantized states in 1 ML Pb islands at 0.55 eV below Fermi level

Observation of localized energy state at 0.3 eV below Fermi level on Si(111)-(6x6)Au

Theoretical modeling shows significant impact of tip properties on I(V) curves

Abstract

The electronic structure of Si(111)-(6x6)Au surface covered with submonolayer amount of Pb is investigated using scanning tunneling spectroscopy. Already in small islands of Pb with thickness of 1 ML Pb$_{(111)}$ and with the diameter of only about 2 nm we detected the quantized electronic state with energy 0.55 eV below the Fermi level. Similarly, the I(V) characteristics made for the Si(111)-(6x6)Au surface reveal a localized energy state 0.3 eV below the Fermi level. These energies result from fitting of the theoretical curves to the experimental data. The calculations are based on tight binding Hubbard model. The theoretical calculations clearly show prominent modification of the I(V) curve due to variation of electronic and topographic properties of the STM tip apex.