Disorder induced local density of states oscillations on narrow Ag(111) terraces

TL;DR

This study investigates how disorder on narrow Ag(111) terraces affects local density of states and standing wave patterns, revealing contrast reversals and confinement effects through STM mapping and theoretical calculations.

Contribution

It provides detailed experimental and theoretical analysis of disorder-induced effects on surface-state electron behavior on Ag(111) terraces.

Findings

Disordered terraces show contrast reversals in dI/dV maps depending on voltage polarity.

Standing wave patterns are observed parallel to step edges in disordered terraces.

Theoretical scattering calculations reproduce observed spatial oscillations and contrast features.

Abstract

The local density of states of Ag(111) has been probed in detail on disordered terraces of varying width by dI/dV-mapping with a scanning tunneling microscope at low temperatures. Apparent shifts of the bottom of the surface-state band edge from terrace induced confinement are observed. Disordered terraces show interesting contrast reversals in the dI/dV maps as a function of tip-sample voltage polarity with details that depend on the average width of the terrace and the particular edge profile. In contrast to perfect terraces with straight edges, standing wave patterns are observed parallel to the step edges, i.e. in the non-confined direction. Scattering calculations based on the Ag(111) surface states reproduce these spatial oscillations and all the qualitative features of the standing wave patterns, including the polarity-dependent contrast reversals.