Band bending and ratcheting explain triboelectricity in a flexoelectric contact diode

TL;DR

This study demonstrates that flexoelectric band bending caused by asperity contacts drives triboelectric charge transfer, supported by quantitative experiments with a conductive AFM probe on Nb-doped SrTiO3, revealing a ratcheting mechanism.

Contribution

The paper provides the first quantitative experimental validation of a model where flexoelectric band bending explains triboelectricity in non-metals.

Findings

Quantitative agreement between model predictions and experimental current-bias data.

Evidence of a ratcheting mechanism in triboelectric charge transfer.

Flexoelectric band-bending is fundamental to triboelectric contacts.

Abstract

Triboelectricity was recognized millennia ago, but the fundamental mechanism of charge transfer is still not understood. We have recently proposed a model where flexoelectric band bending due to local asperity contacts drives triboelectric charge transfer in non-metals. While this ab-initio model is consistent with a wide range of observed phenomena, to date there have been no quantitative analyses of the proposed band bending. In this work we use a Pt$_{\mathrm{0.8}}$Ir$_{\mathrm{0.2}}$ conductive atomic force microscope probe to simultaneously deform a Nb-doped SrTiO$_{\mathrm{3}}$ sample and collect current-bias data. The current that one expects based upon an analysis including the relevant flexoelectric band-bending for a deformed semiconductor quantitively agrees with the experiments. The analysis indicates a general ratcheting mechanism for triboelectric transfer and strong experimental evidence that flexoelectric band-bending is of fundamental importance for triboelectric contacts.