Nanomechanical Characterization on Zinc and Tin Oxides Nanobelts
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Nanomechanical Characterization on Zinc and Tin Oxides Nanobelts Minhua Zhao1 Scott Mao1, Zhong Lin Wang2 Fengting Xu3 and John A Barnard3 1 Department of Mechanical Engineering, Univ. of Pittsburgh, Pittsburgh, PA 15261 2 School of Materials Sci. & Engr. , George Institute of Technology, Atlanta, GA 30332-0245 3 Department of Materials Sci. & Engr., Univ. of Pittsburgh, Pittsburgh, PA 15261
ABSTRACT Nanobelts are a group of materials that have a rectangle-like cross section with typical widths of several hundred nanometers, width-to-thickness ratios of 5 to 10, and lengths of hundreds of micron meters. In this paper, nanoindentations were made on individual ZnO, SnO2 nanobelts and (0001) bulk ZnO by using AFM and Hysitron Triboscope indenters. It was shown that the indentation size effect was still obvious for the indentation depth under 50 nm. It is also demonstrated that nanomaching is possible on nanobelt using AFM tip.
INTRODUCTION In recent years, quasi one-dimensional (1D) solid nanostructure (nanowires and nanobelts) have stimulated considerable interest for scientific research due to their importance in mesoscopic physics studies and their potential applications. Compared to micrometer diameter whiskers and fibers, these nanostructures are expected to have remarkable optical, electrical, magnetic, and mechanical properties. Exploration of novel methods for large-scale synthesis of 1D nanostructure is a challenging research area. As n-type semiconductive materials, zinc oxide (ZnO) has received a considerable amount of attention over last few years because of many applications it has found in various fields. ZnO is now widely used as transparent conducting oxide materials and gas sensors. In particular, ZnO is regarded as a promising candidate material for flat panel displays because of its high electrical conductivity, high optical transparency as well as its low cost and easy etchability. Recently, Wang’s group [1-3] has successfully synthesized the belt-like oxides (so called nanobelts) by evaporating ZnO or SnO2 powders at high temperatures without the presence of catalyst. The beltlike morphology is distinct from those of semiconductor nanowires. With a well-defined geometry and perfect crystallinity, the semiconducting oxide belts are likely to be a model materials family for understanding mechanical behavior at nano-scale with absence of dislocations and defects (excluding point defects). The dimension of the nanobelt as a mechanical cantilever potentially can be used as a mechanical resonator, or as electro-optical resonator. Due to its small dimension, the natural frequency (resonance) of the nanobelt, as a resonator could be very high. Since the nanobelt can be used as nanomechanical device, it is important to measure its elastic Young’s modulus and strength as well as fracture stress. The nanobelts provide an ideal object for characterizing the mechanical behavior of defect-free semiconducting oxides at nano-scale. In this study, nano-scale mechanical properties of individual zinc oxide
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