Damon Hebert

After first joining the Rockett Group as a graduate student, Damon initially worked on deposition of CuInSe2 thin films using the group's unique hybrid sputtering and evaporation process. He used characterization techniques such as SEM, profilometry and SIMS to study the material. After having fabricated the worldŐs first isolated CuInSe2 grain boundary for study in epitaxial material (with the help of co-worker Allen Hall), Damon focused on electrical and optical properties of the thin film solar cell absorber material and the grain boundaries therein, studying both the isolated single grain boundary and polycrystalline device-quality layers from outside laboratories.

The electrical work involved the resurrection and modernization of a defunct low temperature Hall effect machine left. The machine has been successful in characterizing materials that are moderately resistive. It is able to measure resistivity, Hall coefficient and I-V curves down to approximately 20 K.. The optical work includes spectrophotometry, photoluminescence (PL) and cathodoluminescence (CL); techniques that shed light on defects and recombination in CuInSe2 and related materials. Damon completed his thesis working closely with staff scientists Dr. Julio Soares in the MRL's Laser and Spectroscopy Facility on a PL excitation experiment, an experiment in which the PL excitation wavelength is tuned in order to probe specific transitions within the bandgap of the CIGS absorber layer. Damon also worked closely with staff scientist Dr. James Mabon in the MRLŐs Center for Microanalysis of Materials using a scanning electron microscope to analyze recombination emissions from grains and grain boundaries of CIGS films on a nanoscale using correlated CL and electron backscatter diffraction (EBSD). Damon's work elucidated the impact of grain boundaries on defect distribution and behavior with respect radiative emissions. Damon's CL+EBSD experiments were the first of their kind performed on selenide absorber layers. They were especially unique in that they were performed on both cross-sectioned thin films as well as plan-view samples that were planarized in two ways - with an ion polisher and by a unique backside peeloff method. Damon's work was able to separate the effects of topography from emission behavior and instead focus on the emission behavior from grain boundaries whose locations were specifically located with EBSD. Finally, Damon's thesis analyzed the effects of Na, Ga and Cu contect,as well as CdS deposition, on emission characteristics.

Damon collaborated as an academic consultant with San Jose, CA, based thin film CIGS solar manufacturer Nanosolar, Inc., from 2010-2011. He conducted characterization studies on Nanosolar samples using a bevy of MRL microanalysis techniques such as PL, PLE, CL, XRD, SIMS and FTIR. He included a chapter in his thesis on the effects of low-temperature annealing on emission characteristics of CIGS and CdS thin films based on this collaboration.

Damon also has worked on several projects that were not directly related to his thesis work. In October 2006, Damon visited the Hahn Meitner Institute (now the Helmholtz-Zentrum) in Berlin to work with Susanne SiebentrittŐs heterogeneous PV materials group. There he completed a project on symmetry of native defects in the tetragonal semiconductor CuGaSe2, a polarization-dependent PL study. Earlier that year, Damon visited Len BrillsonŐs group at Ohio State University to work on low temperature CL of epitaxial and polycrystalline CuInSe2. From 2006-2009, the Rockett group collaborated with the Pacific Northwest National Laboratory on a project to fabricate contacts to CdGeAs2, a potential material for high energy radiation detectors. Damon and co-worker Angel Aquino performed electrical and optical measurements on CdGeAs2. Damon has published a paper with the Journal of the American Ceramics Society, titled "Kelvin probe force microscopy of metal contacts on amorphous cadmium germanium arsenide", which is in press.

Damon defended his thesis in August of 2012 and has since been working as a post-doctoral researcher within the Rockett group. He has been collaborating with the University of Oregon on a project entitled "Enhanced photovoltaic efficiency through heterojunction assisted impact ionization". He has been performing annealing studies on C-implanted Si and CIGS/CdS heterojunctions with the hope of generating multiple electron hole pairs per incident photon through impact ionization. He has been using XRD and SIMS for analysis.

Damon has also served as Treasurer of the UIUC Student Chapter of the American Vacuum Society, and was a founding member of the student chapter in 2006. The student chapter runs outreach and science education events, supports student participation in national and local symposia, organizes field trips to science centers (such as Argonne and FermiLab), and arranges campus colloquia on current science topics.

To contact Damon, email him at damonhebert at gmail dotcom

Publications

"Photoluminescence and Photoluminescence Excitation Spectroscopy of Cu(In,Ga)Se2 Thin Films", Damon N. Hebert, Julio A.N.T. Soares, Angus A. Rockett, Mater. Res. Soc. Symp. Proc. Vol. 1165 © 2009

"Polarized Luminescence of Defects in CuGaSe2", Susanne Siebentritt, Sven Augustin, Niklas Papathanasiou, Damon Hebert, Angus Rockett,Jurgen Blasing, and Martha Ch Lux-Steiner, Mater. Res. Soc. Symp. Proc. Vol. 1012 © 2007

"Synthesis and characterization of bulk, vitreous cadmium germanium arsenide", Johnson,Bradley R.; Riley,Brian J.; Sundaram,Shanmugavelayutham K.; Crum,Jarrod V.; Henager,Charles H.; Zhang,Yanwen; Shutthanandan,Vaithiyalingam; Seifert,Carolyn E.; Van Ginhoven, Renee M.; Chamberlin,Clyde E.; Rockett,Angus A.; Hebert,Damon N.; Aquino,Angel R., J Am Ceram Soc, 2009, 92, 6, 1236-1243.

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Professor Angus A. Rockett • Phone: (217) 333-0417 • Fax: (217) 333-2736 • Email: arockett@uiuc.edu