Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation.

Dave Maharaj,Bharat Bhushan

doi:10.3762/bjnano.5.94

Abstract

Nanoscale research of bulk solid surfaces, thin films and micro- and nano-objects has shown that mechanical properties are enhanced at smaller scales. Experimental studies that directly compare local with global deformation are lacking. In this research, spherical Au nanoparticles, 500 nm in diameter and 100 nm thick Au films were selected. Nanoindentation (local deformation) and compression tests (global deformation) were performed with a nanoindenter using a sharp Berkovich tip and a flat punch, respectively. Data from nanoindentation studies were compared with bulk to study scale effects. Nanoscale hardness of the film was found to be higher than the nanoparticles with both being higher than bulk. Both nanoparticles and film showed increasing hardness for decreasing penetration depth. For the film, creep and strain rate effects were observed. In comparison of nanoindentation and compression tests, more pop-ins during loading were observed during the nanoindentation of nanoparticles. Repeated compression tests of nanoparticles were performed that showed a strain hardening effect and increased pop-ins during subsequent loads.

Highlights

The characterization of mechanical properties is crucial for a fundamental understanding of materials behavior during contact
First, hardness, creep and strain rate data are shown for a thin Au film (100 nm)
Results for nanoindentation using a Berkovich tip and compression using a flat punch are given for Au nano-objects

Summary

Introduction

The characterization of mechanical properties is crucial for a fundamental understanding of materials behavior during contact. Enhanced mechanical properties were observed in nano-objects [18,19,20,21,22,23] made of various materials including Au, Cu, Nb and Ni, for which decreasing diameters result in an increase in micro/nanoobject yield stress and hardness.

Results

Conclusion