Preparation of ZnO Nanowire transistors: using Nanotransfer and dielectrophoresis to fabricate electrodes

• Main Authors: Ho-Chien Su, 蘇和堅
• Other Authors: Yi-Chang Chung
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/53383912789337211357

碩士 === 國立高雄大學 === 化學工程及材料工程學系碩士班 === 98 === Nanotransfer technique has been developed as the next generation of nanolithography because of its low cost, rapid processing, and high throughput, as compared with traditional photolithography. The study applied the nanotransfer technique to fabricate the gold electrodes, and dielectrophoresis to align ZnO nanowires in order to assemble a transistor. The ZnO nanowire is n-type of semiconductor with a wide band gap. Its single crystalline type can significantly promote the carrier mobility and also perform high surface-to-volume ratio, leading to its potential in gas sensing and optoelectronics. Four parts in the study were included: (1) Preparation of ZnO nanowires by hydrothermal methods. (2) Nanotransfer techniques to fabricate gold electrodes by using UV-curable polymers as the adhesion and dielectric layer. (3) Alignment of nanowires by dielectrophoresis methods. (4) Measurement of electric properties of transistors. Firstly, we employed a two-staged hydrothermal method to prepare high-quality, single-crystalline ZnO nanowires. By changing the processing periods, the lengths of the nanowires were under control. Furthermore, by adjusting UV-curable polymer recipes, the dielectric and adhesion layer was spin-coated and UV-cured on a substrate to transfer gold electrodes. The novel technique was to use PDMS to cover the top of the adhesion layer and then to perform UV irradiation. The high oxygen diffusion in PDMS film led to partial curing on the outmost surfaces of the adhesion layer, enabling the use of adhering to gold-coated layer at 80 oC. We also added a multi-thiol compound to lower the surface Tg and enhance the adhesion force of the adhesion layer, resulting in successful transfer at room temperature. Atomic force microscopy was used to analyze the surface morphologies and the changes of adhesion force on the various adhesion surfaces with changing operating temperatures. The mechanism of metal transfer and the operation conditions of nanotransfer were also investigated. Using dielectrophoresis techniques could align the ZnO nanowires on the electrode mold under 1 MHz of AC within 2 min. The adhesion layer was then used to transfer nanowires and gold electrode simultaneously, ensuring well contact between wires and electrodes. In the measurement of electric properties, the nanowire transistor displayed a threshold voltage of 3V, a current on/off ratio of 6, a carrier mobility as high as 348.4cm2/Vs, a transconductance of 2.55 μS, and a subthreshold slope of 3.72V/dec。Then will use the PMMA and adhesive layer to form composite insulation layer, so as to increase the stability of electrical components.