| AVS 58th Annual International Symposium and Exhibition | |
| Applied Surface Science Division | Tuesday Sessions |
| Session AS-TuA |
| Session: | Imaging and 3D Chemical Analysis - Part II |
| Presenter: | Patrick Kung, University of Alabama |
| Authors: | N. Dawahre, University of Alabama G. Shen, University of Alabama W. Baughman, University of Alabama S. Balci, University of Alabama S. Wilbert, University of Alabama N. Harris, University of Alabama L. Butler, University of Alabama S. Kim, University of Alabama P. Kung, University of Alabama |
| Correspondent: | Click to Email |
Wide bandgap ZnO based semiconductors are materials of great importance in an increasingly large number of optoelectronic devices for energy applications, including high efficiency low cost photovoltaics, solid-state lighting, ultraviolet light emitting and laser diodes, transparent electronics, transparent conducting windows that can be a potentially cheaper and more abundant substitute to ITO for photonic devices, and higher performance scaffold than TiO2 in sensitized solar cells. The material’s wide bandgap, large exciton binding energy, and piezoelectricity can now be exploited at the nanoscale through the realization of nanobelts, nanoribbons and nanowires, leading to a dramatically expanded range of applications (e.g. chemical sensors and mechanical energy harvesting devices, etc). Enhancing our understanding of the chemical purity of ZnO nanostructures and understanding of the interfaces in ZnO based nano-heterostructures with atomic resolution is essential in order to enable the development of novel devices while further improving the performance of existing ones.
In this talk, we report the use and development of atom probe tomography (APT) in order to image the chemical composition of well aligned ZnO nanowires synthesized by thermal chemical vapor deposition and its relation to other material spectroscopic characteristics. The ZnO nanowires used were on various substrates, including sapphire, GaN and Si. The nanowires were single crystalline, 0.5-20 um long with a diameter controllable from 50 to 150 nm and a density on the order of 10^8 per cm^2.
We subsequently discuss the sample preparation techniques employed and the influence of various APT measurement parameters on the quality of the data collected. Atoms probe tomography (APT), which combines a field ion microscope and a time-of-flight mass spectrometer, is an analytical technique which is unmatched in identifying composition at the atomic scale and in 3D. However, proper interpretation of the APT data required thorough analysis of the mass spectra. Data analysis was also carried out in correlation with the nanowire synthesis conditions (e.g. carrier gas and dopant) and with other characterization techniques aimed at assessing the nanowire optical and electrical properties. These included high resolution transmission electron microscopy along with energy dispersive spectroscopy mapping, confocal Raman spectroscopy and imaging, confocal photoluminescence and imaging, as well as terahertz time domain spectroscopy.