Atomic-Scale Friction Studies on Single-Crystal Gallium Arsenide Using Atomic Force Microscope and Molecular Dynamics Simulation

Pengfei Fan,Hari M Upadhyaya,Xichun Luo,Saurav Goel

doi:10.1007/s41871-021-00109-3

Abstract

This paper provides a fresh perspective and new insights into nanoscale friction by investigating it through molecular dynamics (MD) simulation and atomic force microscope (AFM) nanoscratch experiments. This work considered gallium arsenide, an important III–V direct bandgap semiconductor material residing in the zincblende structure, as a reference sample material due to its growing usage in 5G communication devices. In the simulations, the scratch depth was tested as a variable in the fine range of 0.5–3 nm to understand the behavior of material removal and to gain insights into the nanoscale friction. Scratch force, normal force, and average cutting forces were extracted from the simulation to obtain two scalar quantities, namely, the scratch cutting energy (defined as the work performed to remove a unit volume of material) and the kinetic coefficient of friction (defined as the force ratio). A strong size effect was observed for scratch depths below 2 nm from the MD simulations and about 15 nm from the AFM experiments. A strong quantitative corroboration was obtained between the specific scratch energy determined by the MD simulations and the AFM experiments, and more qualitative corroboration was derived for the pile-up and the kinetic coefficient of friction. This conclusion suggests that the specific scratch energy is insensitive to the tool geometry and the scratch speed used in this investigation. However, the pile-up and kinetic coefficient of friction are dependent on the geometry of the tool tip.

Highlights

Gallium arsenide (GaAs) is one of the hard-brittle materials with desirable characteristics, such as hightemperature resistance [1], large bandgap [2], and high electronic mobility [3] making it superior to silicon as a semiconductor material
The pile-up occurred on one side, similar to the condition observed during the molecular dynamics (MD) simulation
The following conclusions can be drawn from the aforementioned discussions: 1. A strong size effect was observed during GaAs nanoscratching at depths below 2 nm in the MD simulations and at depths below 15 nm in the atomic force microscope (AFM) experiments

Summary

Introduction

Gallium arsenide (GaAs) is one of the hard-brittle materials with desirable characteristics, such as hightemperature resistance [1], large bandgap [2], and high electronic mobility [3] making it superior to silicon as a semiconductor material. According to the literature review, many molecular dynamics (MD) studies were published during the last decade and further studies on nanomachining of GaAs are emerging These studies shed light on aspects of crack formation [15] during singlepoint diamond turning (SPDT), plastic deformation of GaAs [16], and the material removal mechanism during chemo-mechanical polishing [17]. These studies did not address aspects of the size effect observed in GaAs much like the other brittle materials, and they did not clarify whether the kinetic COF is a sufficiently robust indicator to compare simulations and experiments, especially in this era of the digital twin. A well-planned experiment and MD simulation methodology were developed by undertaking a thorough investigation to obtain various insights that are relevant to the cost-effective nanomanufacturing of GaAs; this effort is considered a novel one

Methods

Results

Conclusion