Elastic modulus of single-crystal GaN nanowires
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Guosheng Cheng Departments of Electrical Engineering and Applied Physics, Yale University, New Haven, Connecticut 06520
Robert Klie Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (Received 15 March 2006; accepted 29 June 2006)
The deformation behavior of single-crystal GaN nanowires was studied by directly performing three-point bending tests on each individual nanowire in an atomic force microscope. The elastic modulus calculated from the load–displacement response of the nanowires was 43.9 ± 2.2 GPa. Single-crystal GaN nanowires investigated in this study were synthesized by chemical vapor deposition techniques based on the vapor–liquid–solid growth mechanism and had a diameter range from 60 to 110 nm. Crystalline GaN nanowires did not show obvious plastic deformation in bending and usually failed in a brittle manner.
I. INTRODUCTION
One of the major goals of nanoscience and technology is to build ultrasmall (nano/microscale) structures with electrical, electronic, and photonic properties and mechanical integrity superior to their conventional counterparts. Crucial to this building process is the creation of fully functional nanoscale building blocks of various sizes and shapes.1,2 To meet this demand, various methods, such as metalorganic chemical vapor deposition (MOCVD),3 chemical vapor deposition (CVD),4,5 laser ablation,6 sol-gel,7 and thermal evaporation8 have been successfully used to produce a variety of nanowires/ nanotubes, such as C,9,10 Si,11,12 SiO2,4,13 and GaN14,15; nanorods16,17; nanobelts18; and even nanorings.19 GaN epitaxial films and devices have attracted considerable attention because of their broad applications in blue/green light emitting diodes,20,21 laser diodes and photodetectors,3,15 and high-power/high-temperature electronics.2 At the same time, more and more efforts have been made involving GaN one-dimensional nanostructures, such as nanowires and nanotubes. Individual GaN nanowire field-effect transistors feature high mobility and relatively low carrier density with a promising nanoscale functional unit for further integration technology based on a bottom-up approach.22–24 Very recently, a nanoscale GaN diode was demonstrated both in
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0350 2882
http://journals.cambridge.org
J. Mater. Res., Vol. 21, No. 11, Nov 2006 Downloaded: 12 Apr 2015
a single nanowire2,25 and in a building block by crossing n-GaN and p-Si nanowires.26,27 Furthermore, both optically and electrically pumped nanoscale GaN lasers in the nanowires have been reported so far.3,28 However, to integrate these nanoscale units into complex functional nanodevices, developing a precise mechanical design criterion based upon the known mechanical properties is of significant importance because mechanical failure of any nano building block may lead to the malfunction or even fatal failure of the entire device. Unfortunately, discussion of the mechanical properties of GaN nanowires i
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