The Impact of Hydrogen Plasma Treatments at Moderate Temperatures on Sintered Zinc Oxide Samples - Evidence for Hydrogen
- PDF / 128,875 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 16 Downloads / 149 Views
0957-K10-40
The Impact of Hydrogen Plasma Treatments at Moderate Temperatures on Sintered Zinc Oxide Samples - Evidence for Hydrogen Induced Nano-Void Formation Reinhart Job Department of Mathematics and Computer Science, University of Hagen, Haldener Str. 182, Hagen, D-58084, Germany ABSTRACT Using µ-Raman spectroscopy (µRS) analyses, the impact of hydrogen plasma treatments on sintered zinc oxide (ZnO) samples was investigated. H-plasma exposures (150 W, 13.56 MHz) were carried out for 1 hour at substrate temperatures between 250 °C and 500 °C. µRS reveals that plasma hydrogenated ZnO samples are more defective than non-treated ones. On one hand non-specified defect species are created with a maximal density upon plasma hydrogenation at 350 °C, on the other hand the formation of oxygen vacancies (VO) can be traced. The density of VO defects, appearing upon H-plasma exposure, is not significantly correlated to the applied substrate temperatures. µRS also reveals vibration modes of H2 molecules trapped in nano-voids. The µRS results indicate that those nano-voids are created by the coalescence of VO defects. INTRODUCTION ZnO is a wide band gap semiconductor (∼3.3 eV at 300 K), which provides a wide range of promissing electronic, optical and mechanical applications. In particular, ZnO has a large exciton binding energy (∼60 meV), which makes the fabrication of low-threshold excitonic laser diodes possible [1, 2]. Furthermore, sintered ZnO is a well developed ceramic material for varistor devices; their performance is highly dependend on defects and micro-structural disorder [3]. Recently, the interaction of hydrogen with ZnO became an important research focus, since hydrogen has a significant impact on the defect structure and is also suspected to generate a shallow donor state in ZnO (e.g. [1, 2]). Hydrogen plasma treatments are an important process tool for the hydrogen incorporation into ZnO substrates. To investigate the impact of the H-plasma on sintered ZnO samples, H-plasma treatments at various moderate substrate temperatures between 250 °C and 500 °C were carried out. The plasma hydrogenated ZnO samples were analyzed by µRS. It turned out that this analytical tool provides a good basic insight about hydrogen related damage and the formation of nano-voids in ZnO. EXPERIMENTAL ZnO pellets were prepared from high purity ZnO powder (Merck). To stiffen the pellets, an amount of 8 g ZnO powder was mixed with 5 ml of a solution of the acrylic resin Elvacite® and acetone. This mixture was manually homogenized by stirring. During this procedure the acetone evaporates. The homogenized mixture is finally mortared and pressed to pellets (diameter: ∼2 cm, thickness: ∼3 mm), which were cut into smaller pieces (ca. 5 × 5 × 3 mm3) for further processing. The samples were sintered in a vacuum furnace at a pressure of ∼10-5 mbar. The applied heating profile had a maximum temperature of 900 °C, which was attained after conducting a linear heating ramp from room temperature up to 900 °C within 1 hour. After annealing at 900
Data Loading...
