Mechanical and electrical properties of a nano-gap or how to play the nano-accordion

TL;DR

This study uses in-situ TEM to explore how nano-gaps and crystal orientations affect the electrical and mechanical properties of a layered compound, revealing the influence of adsorbed molecules and environmental conditions.

Contribution

It introduces a novel in-situ TEM device for analyzing the relationship between (thermo)electric properties and crystal orientation at nano-scale gaps.

Findings

Nano-sized gaps can be mechanically controlled via heating currents.

Electrical properties are significantly affected by the gap and environment.

Adsorbed molecules influence electrical behavior even in high vacuum.

Abstract

In-situ transmission electron microscopy (TEM) has become an important technique to study dynamic processes at highest spatial resolution and one branch is the investigation of phenomena related with electrical currents. Here, we present experimental results obtained from a peculiar in-situ TEM device, which was prepared with the aim to analyze the relationship between (thermo)electric properties and specific crystal orientations of a misfit layered compound. The formation of a nano-sized gap at a grain boundary facilitated a precisely controllable mechanical bending of the device by application of differential heating currents. The devices' electrical properties were found to be substantially influenced by the gap, leading to a high intrinsic voltage. This voltage additionally depends on the vacuum environment and on the history of applied heating currents. These findings are largely attributed to the presence of adsorbed molecules within the gap region. The electrical in-situ TEM studies of this work illustrate that interior surfaces can strongly influence electrical properties even under high vacuum conditions.