A Facile Method for Patterning Substrates with Zinc Oxide Nanowires
- PDF / 658,890 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 271 Views
1174-V07-01
A Facile Method for Patterning Substrates with Zinc Oxide Nanowires
Jeong-Hyun Cho1, Elizabeth W. Cha2, and David Gracias1,3 1
Department of Chemical and Biomolecular Engineering, Johns Hopkins University,
Baltimore, MD 21218, U.S.A. 2
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218,
U.S.A. 3
Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, U.S.A.
ABSTRACT Conventional growth of zinc oxide (ZnO) nanowires (NWs) is typically carried out using vapor liquid solid (VLS) and chemical vapor deposition (CVD) methods. While these methods are effective, they often involve the use of specialty gasses and equipment. We have discovered that ZnO NWs grow spontaneously from zinc (Zn) films (thermally evaporated on silicon (Si) substrates) when the films are merely heated on a hot-plate in air at ambient pressures for 10 minutes. This process does not involve any metal catalysts, seed layers, specialty gasses or surface treatments in forming patterned regions (on silicon substrates) of NWs with typical diameters in the range of 20-50 nm and lengths of 2-3 µm.
INTRODUCTION As a material, bulk zinc oxide (ZnO) is a wide energy band gap semiconductor with a band gap of 3.37 eV and a large exciton binding energy of 60 meV [1]. Additionally, ZnO crystals show piezoelectric properties. ZnO is used in a large variety of products ranging from sunscreen to light emitting diodes (LED). On the nanoscale, ZnO structures possess electrical, chemical, mechanical and optical properties giving them the capability to improve current devices and aid in the development of new technologies. Conventional growth of ZnO nanowires (NWs) is carried out using vapor liquid solid (VLS) and chemical vapor deposition (CVD) methods. These methods typically require specialty gasses, a catalyst and sometimes specialty reaction vessels. Catalytic or seed layer impurities can alter the electronic properties of ZnO NWs and hence these catalytic methods are not ideal, especially when the NWs are used to construct electronic or optical components such as diodes or resonators. There are some methods to grow ZnO NWs on silicon (Si) substrates without the use of any catalysts or seed layers but they involve the use of surface modification of the substrate such as by mechanical scratching, polishing, or chemical etching. It has been argued that the nucleation of ZnO on Si substrates is hard to achieve due to a large lattice mismatch between
ZnO and Si [2]. Hence, in order to grow NWs without the use of pre-nucleant materials, surface treatments are employed [3]. There are still other methods that do not utilize any catalysts, namely seed layers or surface modification, but these methods have either been shown to work with only bulk zinc pieces [4] or require high temperatures (1300 oC) [5]; these processes make it difficult to integrate ZnO NWs with conventional electronic fabrication processes. Recently, we have discovered that ZnO nanowires grow spontaneously, when thermally evaporated Zn
Data Loading...
