Polarity-dependent Electroadhesion at Silicon Interfaces with Nanoscale Roughness

TL;DR

This study investigates how electroadhesion at silicon interfaces with nanoscale roughness depends on polarity and bias, revealing mechanisms that enhance adhesion and friction for precision applications.

Contribution

It provides a detailed measurement and modeling of electroadhesion at nanoscale rough silicon interfaces, highlighting polarity-dependent effects and the role of charge mobility.

Findings

Electroadhesion can be modeled with a boundary element contact model.

Polysilicon exhibits electroadhesion only under positive bias.

Electrostatic interactions significantly enhance adhesion and friction.

Abstract

We measure and model electroadhesion across multi-asperity silicon interfaces with nanometer scale roughness. When electrically biased, our naturally oxidized silicon interfaces display a leakage current consistent with the Fowler-Nordheim model and electroadhesion that can be successfully captured using a boundary element contact model. We show that polysilicon exhibits electroadhesion only under positive bias applied to the substrate monocrystalline wafer, which we interpret as a result of the reduced mobility of holes, with respect to electrons, within polysilicon. Overall, our findings reveal that electrostatic interactions can significantly enhance adhesion and friction between stiff and smooth surfaces, which can be important for example in precision positioning applications.