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Elastic Stability and Piezoelectric Power Generation Using ZnO Nanostructures
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-65405ISBN: 978-91-7393-361-2 (print)OAI: oai:DiVA.org:liu-65405DiVA: diva2:395467
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
List of papers
1. Buckling of ZnO nanowires under uniaxial compression
Open this publication in new window or tab >>Buckling of ZnO nanowires under uniaxial compression
2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Applied Physics Letters, Vol. 92, no 10, 103118- p.Article in journal (Refereed) Published
Abstract [en]

Instability and buckling characterization of vertical well aligned single crystal of ZnO nanowires grown on SiC substrate was done quantitatively by nanoindentation technique. The critical load was found to be 477 μN and the corresponding buckling energy was 3.46× 10-11 J. Based on the Euler model for long nanowire and Johnson model which is an extension of the Euler model for intermediate nanowire, the modulus of elasticity of single wire was calculated. Also, the critical buckling stress and strain were determined for the as grown single wire of ZnO. We found how the modulus of elasticity is dependent on the slenderness ratio. © 2008 American Institute of Physics.

Keyword
Nanotechnology, nanomechanics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-42104 (URN)10.1063/1.2894184 (DOI)60573 (Local ID)60573 (Archive number)60573 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
2. Buckling and mechanical instability of ZnO nanorods grown on different substrates under uniaxial compression
Open this publication in new window or tab >>Buckling and mechanical instability of ZnO nanorods grown on different substrates under uniaxial compression
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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.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-49654 (URN)10.1088/0957-4484/19/41/415708 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
3. Bending flexibility, kinking, and buckling characterization of ZnO nanorods/nanowires grown on different substrates by high and low temperature methods
Open this publication in new window or tab >>Bending flexibility, kinking, and buckling characterization of ZnO nanorods/nanowires grown on different substrates by high and low temperature methods
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2008 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, no 10, 104306- p.Article in journal (Refereed) Published
Abstract [en]

Nanomechanical tests of bending flexibility, kinking, and buckling failure characterization of vertically aligned single crystal ZnO nanorods/nanowires were performed quantitatively by nanoindentation technique. These nanostructures were grown by the vapor liquid solid (VLS) method, a relatively high temperature approach, and the aqueous chemical growth (ACG) method, a relatively low temperature approach on different substrates, including SiC and Si. The first critical load at the inflection point found for the ZnO nanorods/nanowires grown by ACG method was 105 mu N on the SiC substrates and 114 mu N on the Si substrates. The corresponding buckling energies calculated from the force-displacement curves were 3.15x10(-12) and 2.337x10(-12) J, respectively. Similarly, for the samples grown by the VLS method, the first critical load at the inflection point and the corresponding buckling energies were calculated from the force-displacement curves as 198 mu N and 7.03x10(-12) J on the SiC substrates, and 19 mu N and 1.805x10(-13) J on the Si substrates. Moreover, the critical buckling stress, strain, and strain energy were also calculated for all samples. The strain energy for all samples was much less than the corresponding buckling energy. This shows that our as-grown samples are elastic and flexible. The elasticity measurement was performed for all the samples before reaching the first critical and kinking inflection point, and we subsequently observed the bending flexibility, kinking, and buckling phenomena on the same nanorods/nanowires. We observed that the loading and unloading behaviors during the bending test of the as-grown samples were highly symmetrical, and also that the highest point on the bending curves and the first inflection and critical point were very close. ZnO nanorods/nanowires grown on SiC by the ACG method, and those grown by the VLS method on Si substrates, show a linear relation and high modulus of elasticity for the force and displacement up to the first inflection and critical point. The results also show that the elasticity of the ZnO single crystal is approximately linear up to the first inflection point, is independent of the growth method and is strongly dependent on the verticality on the surface of the substrates. In addition, the results show that after the first buckling point, the nanorods/nanowires have plasticity, and become more flexible to produce multiple kinks.

Keyword
bending, buckling, crystal growth from solution, elastic moduli, II-VI semiconductors, indentation, plasticity, semiconductor quantum wires, zinc compounds
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-16618 (URN)10.1063/1.3018090 (DOI)
Note
Original Publication: Riaz Muhammad, Alimujiang Fulati, Lili Yang, O Nour, Magnus Willander and P Klason , Bending flexibility, kinking, and buckling characterization of ZnO nanorods/nanowires grown on different substrates by high and low temperature methods, 2008, JOURNAL OF APPLIED PHYSICS, (104), 10, 104306-. http://dx.doi.org/10.1063/1.3018090 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2009-02-18 Created: 2009-02-06 Last updated: 2017-12-14Bibliographically approved
4. Buckling and elastic stability of vertical ZnO nanotubes and nanorods
Open this publication in new window or tab >>Buckling and elastic stability of vertical ZnO nanotubes and nanorods
Show others...
2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 3, 034309- p.Article in journal (Refereed) Published
Abstract [en]

Buckling and elastic stability study of vertical well aligned ZnO nanorods grown on Si substrate and ZnO nanotubes etched from the same nanorods was done quantitatively by nanoindentation technique. The critical load, modulus of elasticity, and flexibility of the ZnO nanorods and nanotubes were observed and we compared these properties for the two nanostructures. It was observed that critical load of nanorods (2890 mu N) was approximately five times larger than the critical load of the nanotubes (687 mu N). It was also observed that ZnO nanotubes were approximately five times more flexible (0.32 nm/mu N) than the nanorods (0.064 nm/mu N). We also calculated the buckling energies of the ZnO nanotubes and nanorods from the force displacement curves. The ratio of the buckling energies was also close to unity due to the increase/decrease of five times for one parameter (critical load) and increase/decrease of five times for the other parameter (displacement) of the two samples. We calculated critical load, critical stress, strain, and Young modulus of elasticity of single ZnO nanorod and nanotube. The high flexibility of the nanotubes and high elasticity of the ZnO nanorods can be used to enhance the efficiency of piezoelectric nanodevices. We used the Euler buckling model and shell cylindrical model for the analysis of the mechanical properties of ZnO nanotubes and nanorods.

Keyword
buckling, crystal growth, II-VI semiconductors, semiconductor growth, semiconductor nanotubes, Youngs modulus, zinc compounds
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-20404 (URN)10.1063/1.3190481 (DOI)
Available from: 2009-09-08 Created: 2009-09-07 Last updated: 2017-12-13
5. The impact of ion irradiation on morphology, structure and optical properties of ZnO nanowires
Open this publication in new window or tab >>The impact of ion irradiation on morphology, structure and optical properties of ZnO nanowires
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2008 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Chemically grown ZnO nanowires were irradiated with ions and subsequently investigated by continues wave (cw) photoluminescence (PL) and time resolved PL (TRPL) both at room (300 K) and low (10 K) temperatures, and was compared with the as-grown samples. The ion bombardment was done by using 30 keV argon, and 40 MeV iodine ions using ion fluencies of 3 ×1016 ions/cm2, and 1.3 ×1013 ions/cm2, respectively. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) spectra showed that the morphology and structure of the ion irradiated ZnO nanowires were less damaged. Using the PL and XRD spectra the induced compressive strains in the irradiated samples was calculated. Also there was a decrease and increase in the XRD intensity which had emphasized that some texture modification occurred in the irradiated samples. No severe decomposition of the irradiated samples was observed. The PL measurements showed that the intensity of the near band emission (free exciton) of the irradiated ZnO nanowires was decreased for all irradiating ions, whereas the deep emission band was enhanced for iodine ions and suppressed for argon ions irradiated samples. A blue peak shift (~ 2 meV) of the excitonic emission of the irradiated samples was observed. The TRPL spectra for the as-grown and the irradiated ZnO nanowires were fitted with single and two components time decay constant, respectively.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65402 (URN)
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2014-01-15Bibliographically approved
6. Experimental and finite element method calculation of piezoelectric power generation from ZnO nanowire arrays grown on different substrates using high and low temperature methods
Open this publication in new window or tab >>Experimental and finite element method calculation of piezoelectric power generation from ZnO nanowire arrays grown on different substrates using high and low temperature methods
Show others...
2008 (English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper we investigate the piezoelectric power generation from ZnO nanowire arrays grown using different methods. The ZnO nanowires are grown on n-SiC and n-Si substrates using both the high-temperature vapor liquid solid (VLS) and the lowtemperature aqueous chemical growth (ACG) methods. A conductive atomic force microscope (AFM) is used in contact mode to deflect the ZnO nanowire arrays. A piezoelectric potential across the nanowires is produced and then released via the rectifying behavior of the Schottky barrier at the platinum metal-ZnO interface. We do not observe any substrate effect but the growth method, crystal quality, density, length and diameter (aspect ratio) of the nanowires are found to affect the piezoelectric behavior. These parameters can significantly affect the performance manifested in the observed output voltage signal. Based on these parameters, we compare four nanogenerators under identical conditions. During the AFM scanning in contact mode without biased voltage, the ZnO nanowire arrays grown by the VLS method produce higher and larger output voltage signal of 35 mV compared to ZnO nanowires arrays grown by the ACG method, which produce smaller output voltage signal of 5 mV. We apply finite element (FE) method calculations to investigate the output voltage of ZnO nanowires based nanogenerators with different aspects ratios. From FE results we find that the output voltage of the nanogenerator is decreased above an aspect ratio 80 of ZnO nanowires.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65404 (URN)
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2014-01-15Bibliographically approved

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