Student Research: Julia Deneen Nowak

Characterization of Nanoparticles Using Transmission Electron Microscopy

Julia Deneen Nowak (CEMS)
Advisor: C. Barry Carter (CEMS)

photo of Julia Nowak at computer The inherently small size of nanoparticles and nanoparticle-based structures makes electron microscopy techniques essential for the analysis of these systems. With the capability of investigating structure and chemistry of materials at the atomic level, the transmission electron microscope (TEM) is uniquely suited for the study of nanoscale phenomena. Such resolution is necessary as the properties of nanoparticles will depend on variations at this small scale.

Because size, structure, chemistry, morphology and defects combine to determine their unique properties, several microscopy techniques must be used to characterize fully nanoparticles. My research focuses primarily on using various techniques in the TEM for nanoparticle characterization. High-resolution TEM, used to image individual atomic columns, is an especially powerful technique for characterizing defects and interfaces [1]. Contacts between nanoparticles are characterized using a combination of bright-field imaging and selected-area diffraction [2, 3]. Chemistry variations, surface coatings, and impurities are characterized using a combination of STEM and EDS. Also, in situ studies, including nanoparticle compression and nanowire heating, provide a direct insight into various dynamic processes as they occur [4]. The combination of these various techniques can provide a more complete understanding of the formation mechanisms of these small particles and the origin of their unique properties.

[1] J. Deneen, C. R. Perrey, S. Kumar and C. B. Carter, "Characterization of Defects in ZnS and GaN"; pp. 83-86 in Springer Proceedings in Physics, Vol. 107, Microscopy of Semiconducting Materials , Edited by A. G. Cullis and J. L. Hutchinson, Springer, Oxford, UK, 2005.

[2] J. Deneen, W. M. Mook, W. W. Gerberich and C. B. Carter, "Contacting Nanospheres," Microsc. Microanal. , 12 (suppl.2) 948-949 (2006).

[3] J. Deneen, W. M. Mook, A. Minor, W. W. Gerberich and C. B. Carter, "In Situ Deformation of Silicon Nanospheres," J. Mater. Sci. , 41 4477-4483 (2006).

[4] J. D. Nowak, W. M. Mook, A. M. Minor, W. W. Gerberich and C. B. Carter, "Fracturing a Nanoparticle," Phil. Mag., DOI: 10.1080/14786430600876585 (2006 in press).