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Buckling and mechanical instability of ZnO nanorods grown on different substrates under uniaxial compression
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
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2008 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Nanotechnology, Vol. 19, no 41Article in journal (Refereed) Published
Abstract [en]

Mechanical instability and buckling characterization of vertically aligned single-crystal ZnO nanorods grown on different substrates including Si, SiC and sapphire (a-Al2O3) was done quantitatively by the nanoindentation technique. The nanorods were grown on these substrates by the vapor-liquid-solid (VLS) method. The critical load for the ZnO nanorods grown on the Si, SiC and Al2O3 substrates was found to be 188, 205 and 130 µN, respectively. These observed critical loads were for nanorods with 280 nm diameters and 900 nm length using Si as a substrate, while the corresponding values were 330 nm, 3300 nm, and 780 nm, 3000 nm in the case of SiC and Al2O3 substrates, respectively. The corresponding buckling energies calculated from the force displacement curves were 8.46 × 10-12, 1.158 × 10-11 and 1.092 × 10-11 J, respectively. Based on the Euler model for long nanorods and the J B Johnson model (which is an extension of the Euler model) for intermediate nanorods, the modulus of elasticity of a single rod was calculated for each sample. Finally, the critical buckling stress and strain were also calculated for all samples. We found that the buckling characteristic is strongly dependent on the quality, lattice mismatch and adhesion of the nanorods with the substrate. © IOP Publishing Ltd.

Place, publisher, year, edition, pages
2008. Vol. 19, no 41
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-49654DOI: 10.1088/0957-4484/19/41/415708OAI: oai:DiVA.org:liu-49654DiVA: diva2:270550
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
In thesis
1. Mechanical Characterization and Electrochemical Sensor Applications of Zinc Oxide Nanostructures
Open this publication in new window or tab >>Mechanical Characterization and Electrochemical Sensor Applications of Zinc Oxide Nanostructures
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanotechnology is emerging to be one of the most important scientific disciplines that physics, chemistry and biology truly overlap with each other. Over the last two decades science and technology have witnessed tremendous improvement in the hope of unveiling the true secrets of the nature in molecular or atomic level. Today, the regime of nanometer is truly reached.

ZnO is a promising material due to the wide direct band gap (3.37 eV) and the room temperature large exciton binding energy (60 meV). Recent studies have shown considerable attraction towards ZnO nanostructures, particularly on one-dimensional ZnO nanorods, nanowires, and nanotubes due to the fact that, for a large number of applications, shape and size of the ZnO nanostructures play a vital role for the performance of the devices. The noncentrosymmetric property of ZnO makes it an ideal piezoelectric material for nanomechanical devices. Thus, mechanical characterization of one dimensional ZnO nanostructures including strength, toughness, stiffness, hardness, and adhesion to the substrate is very important for the reliability and efficient operation of piezoelectric ZnO nanodevices. Moreover, owing to the large effective surface area with high surface-to-volume ratio, the surface of one dimensional ZnO nanowires, nanorods, and nanotubes is very sensitive to the changes in surface chemistry and hence can be utilized to fabricate highly sensitive ZnO electrochemical sensors.

This thesis studies mechanical properties and electrochemical sensor applications of ZnO nanostructures.

The first part of the thesis deals with mechanical characterization of vertically grown ZnO nanorods and nanotubes including buckling, mechanical instability, and bending flexibility. In paper I, we have investigated mechanical instability and buckling characterization of vertically aligned single-crystal ZnO nanorods grown on Si, SiC, and sapphire substrates by vapor-liquid-solid (VLS) method. The critical loads for the ZnO nanorods grown on Si, SiC, and sapphire were measured and the corresponding buckling and adhesion energies were calculated. It was found that the nanorods grown on SiC substrate have less residual stresses and are more stable than the nanorods grown on Si and sapphire substrates.

Paper II investigates nanomechanical tests of bending flexibility, kinking, and buckling failure characterization of vertically aligned single crystal ZnO nanorods/nanowires grown by VLS and aqueous chemical growth (ACG) methods. We observed that the loading and unloading behaviors during the bending test of the as-grown samples were highly symmetrical and the highest point on the bending curves and the first inflection and critical point were very close. The results also show that the elasticity of the ZnO single crystal is approximately linear up to the first inflection point and is independent of the growth method.

In Paper III, we quantitatively investigated the buckling and the elastic stability of vertically well aligned ZnO nanorods and ZnO nanotubes grown on Si substrate by nanoindentation technique. We found that the critical load for the nanorods was five times larger than the critical load for nanotubes. On the contrary, the flexibility for nanotubes was five times larger than nanorods. The discovery of high flexibility for nanotubes and high elasticity for nanorods can be utilized for designing efficient piezoelectric nanodevices.

The second part of this thesis investigates electrochemical sensor applications of ZnO nanorods, nanotubes , and nanoporous material.

In paper IV, we utilized functionalized ZnO nanorods on the tip of a borosilicate glass capillary coated with ionophore-membrane to construct intracellular Ca2+ selective sensor. The sensor exhibited a Ca2+-dependent electrochemical potential difference and the response was linear over a large dynamic concentration range, which enabled this sensor to measure Ca2+ concentrations in human adipocytes or in frog oocytes. The results were consistent with the values of Ca2+ concentrations reported in the literature.

In paper V, ZnO nanotubes and nanorods were used to create pH sensor devices. The developed ZnO pH sensors display good reproducibility, repeatability, and long-term stability. The ZnO pH sensors exhibited a pH-dependent electrochemical potential difference over a large dynamic pH range. We found that the ZnO nanotubes provide sensitivity as high as twice that of the ZnO nanorods. The possible reasons of enhanced sensitivity were explained.

Paper VI investigates an improved potentiometric intracellular glucose biosensor based on the immobilization of glucose oxidase on the ZnO nanoporous material. We demonstrated that using ZnO nanoporous material as a matrix material for enzyme immobilization improves the sensitivity of the biosensor as compared to using ZnO nanorods. In addition, the fabrication method of the intracellular biosensor was simple and excellent performance in sensitivity, stability, selectivity, reproducibility, and anti-interference was achieved.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 61 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1323
Keyword
Nanotechnology, Zinc Oxide, nanorods, nanotubes, nanoporous, buckling, electrochemical sensor
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-57297 (URN)978-91-7393-369-8 (ISBN)
Public defence
2010-06-04, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15
Opponent
Supervisors
Available from: 2010-06-16 Created: 2010-06-16 Last updated: 2014-01-15Bibliographically approved
2. Elastic Stability and Piezoelectric Power Generation Using ZnO Nanostructures
Open this publication in new window or tab >>Elastic Stability and Piezoelectric Power Generation Using ZnO Nanostructures
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanotechnology combines the effort between science and engineering using the approaches of either top-to-bottom or bottom-to-top techniques. A hybrid approach of the above techniques is also used for the fabrication of nanodevices. In nanotechnology one and zero dimensional structures are considered as the basic building blocks for multidimensional systems. One dimensional nanostructure such as nanorods, nanowires and nanotubes has become the research core of science and engineering, because of their unique and interesting properties for device applications.

In this thesis a mechanical property i.e. elastic stability, the behavior of piezoelectric power nanogenerator and the effects of ions irradiations were investigated for ZnO nanostructures.

Buckling phenomena was employed for the elastic stability investigation using Hysitron nanoindentor. ZnO nanostructures were loaded axially to a prescribed controlled load and then unloaded in the same fashion by the tip of a nanoindentor to investigate the first critical load and other unstable configurations. The present buckling study concluded that the elastic stability of ZnO nanostructures were mainly dependent on the slenderness ratio and the verticality of the structures to the substrates.

Piezoelectric power nanogenerators were investigated using ZnO nanowires. The performance of different piezoelectric power nanogenerators were observed on the bases of the aspect ratio, density of state, spatial density and the growth methods. A higher and stable voltage signal was generated by the vapor-liquid-solid (VLS) grown samples compared to the aqueous chemical growth (ACG) grown samples. The finite element (FE) method was also used to calculate the expected output voltage signal from ZnO nanogenerator with different aspect ratio. From the FE results we found that the output voltage of the nanogenerator was decreased above an aspect ratio of 80 for ZnO nanowires.

Ions irradiation effects were investigated using ZnO nanowires grown by the ACG method on Si substrate. Iodine and argon ions of energy 40 MeV and 30 keV were used using fluencies of 3 ×1016 ions/cm2, and 1.3 ×1013 ions/cm2, respectively. The results show that heavy and high energy irradiation modifies the morphology, crystalline structure and optical properties of ZnO nanowires.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 104 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1326
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65405 (URN)978-91-7393-361-2 (ISBN)
Public defence
2010-08-27, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2014-01-15Bibliographically approved

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Fulati, AlimujiangZhao, QingxiangNour, OmerWillander, Magnus

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