Experimental measurement of the Young’s modulus of
nanomaterials with dimensions down to 2 nm
Yujie Chen1, Qiang Gao2, Yanbo Wang1, Xiaozhou Liao*, 1, Yiu-Wing Mai1, H. Hoe
Tan2, Jin Zou3, Simon P. Ringer1, 4, and Chennupati Jagadish2
1 School of Aerospace, Mechanical and Mechatronic Engineering, The University of
Sydney, Sydney, NSW 2006, Australia
2 Department of Electronic Materials Engineering, Research School of Physics and
Engineering, The Australian National University, Canberra, ACT 0200, Australia
3 Materials Engineering and Centre for Microscopy and Microanalysis, The University
of Queensland, St Lucia, QLD 4072, Australia
4 Australian Centre of Microscopy and Microanalysis, The University of Sydney,
Sydney, NSW 2006, Australia
*Corresponding author: Email xiaozhou.liao@sydney.edu.au
It has been well known that reducing the dimensions of materials down to the
nanometer regime has significant effects on the mechanical properties of the
materials. Extensive theoretical and experimental investigations have been carried
out to explore various issues in this area. While theoretical investigations have only
been carried out for dimensions smaller than 15 nm because of calculation limitations,
experimental investigations were usually conducted for dimensions larger than 15 nm
due to the sensitivity limit of testing facilities or the inability to decouple thin films from
their underlying bulk substrates.
Here we design an experiment to accurately extract the Young’s modulus (E)
of thin films with thickness down to 2 nm. Amorphous Al2O3 (a-Al2O3) films with a
thickness varying from 2 to 20 nm were conformally coated on single-crystal GaAs
nanowires with a diameter of 100 nm, forming a core/shell nanowire structure. The
Young’s modulus of a-Al2O3 shell can be easily decoupled from that of the nanowire
core. In-situ compression was conducted using Hysitron PicoIndentor® in a
transmission electron microscope. Mechanical data were extracted using finite
element analysis. The Young moduli of the a-Al2O3 shell were then extracted using
the following equation:

E
 t
t2
r3
r 4 
E NW  EC 1  8 S  1 S  3 S2  4 S3  2 S4 
dC
dC
d C 
 EC
 d C

(1)
where ENW is the effective Young’s modulus of a core/shell NW, EC the Young’s
modulus of the GaAs core, ES is the Young’s modulus of the a-Al2O3 shell, and tS and
dC are the shell thickness and core diameter, respectively, for an individual NW. The
Young’s modulus of a-Al2O3 shell increased from 156 to 389 GPa as the shell
thickness decreased from 20 to 2 nm. Moreover, it increases rapidly when the shell
thickness is less than 5 nm.
Reference:
[1] C.Q. Chen, Y.Shi, Y.S. Zhang, J. Zhu and Y.J. Yan, Phys. Rev. Lett. 96, 075505
(2006).