Feb 20, 2009
Handy control of ZnO film texture
Growth of high-quality textured ZnO thin films on a general substrate is of critical importance for technological applications. In practice, a polycrystalline film consists of numerous fine grains whose crystallographic orientations are usually distributed randomly. Control of their orientation distribution can lead to the control of the physical properties of the film itself. In particular, films of ZnO with the very anisotropic wurzite structure can show very different properties depending on the crystalline texture of the film. In addition to changing the films properties, they can serve as seed layers for the growth of nanowires on a general substrate with controlled orientation that enables the tailoring of nanowire array properties.
A team led by Robert Snyder at Georgia Tech has demonstrated a simple but practically very useful technique for controlling the texturing of the ZnO film by controlling laser fluence in a pulsed laser deposition system at room temperature. The team is composed of Jung-il Hong, Joon Ho Bae and Z.L. Wang from the School of Materials Science and Engineering.
By ablating the target material, ZnO, with a laser beam of controlled fluence, the energy of the atoms deposited onto the substrate is adjusted to form a film with a desired crystallographic texture. The team has also demonstrated the use of this textured film as a seed layer to grow the arrays of nanowires that grew in epitaxy with the film. As the film can be deposited on various substrates, the work is expected to expand the application of textured films and aligned nanowires.
ZnO was tested for the current work, but the research team expects to explore the possible extension of the concept to other materials as well. This technique sets the foundation for preparing high-quality textured ZnO films on a general substrate including polymers for growing orientation aligned ZnO nanowire arrays, which have important applications in optoelectronics, electronics, field emission, sensors and energy science.
About the author
The study was carried out at Georgia Institute of Technology. Professor Robert Snyder is chair of the School of Materials Science and Engineering. Dr Jung-Il Hong is a research scientist. Dr Joonho Bae is a postdoctoral researcher in Prof. Zhong Lin Wang’s research group in the School of Materials Science and Engineering, Georgia Tech.