Wurtzite (W)-type ZnO condensates showed preferred orientation {10 1} when deposited on glass substrate by pulsed laser ablation on Zn target in the presence of oxygen. Such an artificial epitaxy depends on the well developed {10 1} surfaces of the condensates, which enabled {10 1}-specific coalescence to form twin and single crystal regardless of the co-deposited Zn. The W-ZnO condensates have decreasing particle size with increasing oxygen flow rate and a considerable residual stress due to the combined effects of rapid heating/cooling and thermal/lattice mismatch with Zn following parallel epitaxy or (01 )W-ZnO//(01 0)Zn; [ 2 3]W-ZnO//[0001]Zn involving {10 1} slip (Part I).
In addition, wurtzite (W)-type ZnO/Zn composite deposit with preferred orientation {10 1}W-ZnO and (0001)Zn respectively on glass substrate in chapter I under Isothermal (600oC) atmospheric annealing caused self-catalyzed vapor-liquid-solid growth of rod-like W-ZnO whiskers with unusual habit. Analytical electron microscopic observations indicated that the W-ZnO whiskers extend along the zone axis of the well-developed polar surfaces {10 1} for a beneficial lower electrostatic energy and surface energy. Alternatively, the whiskers extend via {11 1}-specific growth twinning and/or coalescence twinning for a beneficial fair coincidence-site lattice at the twin boundary (Part II).
Furthermore, Zn particulates overlain with wurtzite (W)-type ZnO condensates having nearly orthogonal {10 1} and {11 1} facets were found to self-catalyze unusual tapered W-ZnO whiskers upon isothermal atmospheric annealing, i.e. thermal oxidation, at 600oC. Analytical electron microscopic observations indicated that such whiskers formed tapered slabs having mosaic {10 1} and {2 1} twinned domains. The tapered whiskers can be rationalized by unconventional vapor-liquid-solid growth, i.e. {hkil}-specific coalescence twinning growth from the ZnO condensates taking advantage of a partially molten bottom source of Zn and the adsorption of atoms at the whisker tips and steps under the influence of capillarity effect (Part III).
Finally, Electron irradiation of nano-size wurtzite (W)-type ZnO condensates with intimate mixture of parallel epitaxial Zn caused {10 1}W slip to form a single domain of rock salt (R)-type core and W-type shell. The two polymorphs follow (1 1)R//(0 11)W; [011]R//[ 2 3]W, i.e. chair type Peierls distortion with additional 38 degree tilting (001)R along the ( 2 0)W plane for a fair match of (10 1)W/(1 1)R, the same as one of the two paths for the back-transformation of R-ZnO into a lower crystal symmetry. The martensitic nucleation of R-type ZnO can be attributed to dynamic migration of interstitials/vacancies, lattice mismatch stress, and capillarity effect.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0729108-175145 |
| Date | 29 July 2008 |
| Creators | Huang, Bang-Hao |
| Contributors | Chang, Liuwen, Ho, New-Jin, Shen, Pouyan, Gan, Der-shin, Lin, Chung-Cherng, Chen, Shuei-Yuan |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0729108-175145 |
| Rights | not_available, Copyright information available at source archive |
Page generated in 0.0023 seconds