Step bunching with both directions of the current: Vicinal W(110) surfaces versus atomistic scale model

TL;DR

This study observes step bunching on vicinal W(110) surfaces induced by current direction, revealing different scaling behaviors and demonstrating instability intervals through atomistic modeling.

Contribution

It provides the first experimental observation of step bunching induced by both current directions and introduces an atomistic model showing surface instability conditions.

Findings

Step bunching occurs with both current directions.

Scaling exponent varies with current direction.

Surface instability exists within specific parameter ranges.

Abstract

We report for the first time the observation of bunching of monoatomic steps on vicinal W(110) surfaces induced by step up or step down currents across the steps. Measurements reveal that the size scaling exponent {\gamma}, connecting the maximal slope of a bunch with its height, differs depending on the current direction. We provide a numerical perspective by using an atomistic scale model with a conserved surface flux to mimic experimental conditions, and also for the first time show that there is an interval of parameters in which the vicinal surface is unstable against step bunching for both directions of the adatom drift.