The Study of Lateral Epitaxial Overgrowth of ZnO Thin Films in Aqueous Solution
| Autor: | Ming-Yang Yu, 余明陽 |
|---|---|
| Rok vydání: | 2014 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 102 In this study, lateral epitaxial overgrowth of ZnO films were implemented in low temperature aqueous solution. The thesis can be divided into two parts: (1) ZnO microrods/polymer composites promote biaxially oriented growth of ZnO films on glass substrates; (2) patterned buffer layer assisted lateral epitaxial overgrowth (LEO) of ZnO films. For preparation of ZnO microrods/polymer composite, we infiltrated polydimethylsiloxane (PDMS) and G1 epoxy into epitaxial ZnO microrod arrays on sapphire substrates, respectively. After curing, the resulting ZnO/polymer composite layers were transferred to glass substrates by peel-off processing. The ZnO microrods embedded in the polymer matrix exhibited their well-defined in-plane alignment. The hydrothermal growth of ZnO were performed on the opposite face of ZnO microrods/polymer composite by immersing it in growth solution containing zinc nitrate, hexamethylenetetramine, and sodium citrate. [0001]-oriented ZnO posts with biaxial alignment can be grown on the composite templates. Due to addition of sodium citrate into growth solution, biaxially oriented ZnO films with a continuous and flat morphology can be obtained through coalescence overgrowth of the ZnO posts. For patterned buffer layer assisted lateral epitaxial overgrowth of ZnO films, patterned epitaxial ZnAl2O4 buffer layers were fabricated by combining lift-off and solid state reaction processing. Two types of masks were used to fabricate stripe windows and hexagonal arrays of circular windows. Hydrothermal epitaxial growth of ZnO grains only occur on the regions where the lattice matched ZnAl2O4 buffer layers were covered. Such selected area growth mechanism promotes lateral epitaxial overgrowth of ZnO films on the sapphire substrates without mask layer assistance. For lateral epitaxial overgrowth of ZnO, we added sodium citrate and KCl into growth solution, respectively, to inhibit the growth in ont-of-plane directions, e.g. [0001], and promote growth in lateral direction. The microstructures corresponding to window and wing regions were systematically investigated by SEM observation and TEM analysis. Also, the optical properties of the LEO ZnO films were studied by photoluminescence. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|