(7ji) Plasma Biomedicine and Plasma-Fabricated Nanomaterials for Energy, Health, and Electronics

Two of the most promising areas of plasma-material interaction research are plasma biomedicine and nanomaterial fabrication/modification, both of which are very dependent on gas-phase plasma chemistry. Plasma biomedicine can enable processes such as sterilization, wound healing, and cancer treatment; nanomaterials have a myriad of uses, such as enabling catalysis, the continuation of Moore’s Law, and the production of low-cost, efficient photovoltaics. Both of these areas have only scratched the tip of the iceberg in terms of their potential. Despite their seeming differences, both are plasma-material interaction techniques that are dependent on the same principles of plasma physics, nonthermal charged gas-surface interactions, and plasma chemistry. My previous research experience has been focused on plasma-material interactions, utilizing both the low-pressure and high-pressure cold, non-thermal plasmas seen in these fields. This background has prepared me for a career in advancing the science of plasma-material interactions for applications that will attract funding from both government and industry and are relevant to materials, energy, and health. My goal as a professor is to build a group that contributes fundamental knowledge and new, innovative diagnostic and synthesis techniques to plasma biomedicine and nanomaterials.

I intend to build upon my postdoctoral work and use my expertise in isolating O atom trends to identify reaction pathways for the production of biologically-active OCl^- in saline and calculate the rate constant for the dominant pathway. In the area of nanomaterials synthesis, I intend to use pulsed biasing and in-situ diagnostics to control and measure the energy per atom in dusty SiH₄ plasmas, allowing for tailored deposition of nanocrystalline and even epitaxial Si thin films for solar energy. An innovative design built upon my Sn etching experience will also be used to produce synthesize SiSn thin films from dusty plasmas. SiSn films have tunable direct bandgaps for photovoltaics and can also be used to fabricate transistors with low leakage currents. Additionally, deposition of nanomaterial catalysts at atmospheric pressure can be accomplished at a high rate by combining nanopulses with a continuous RF plasma. This has possible ramifications for sustainable energy by means of catalyst deposition for CO₂ reforming. Finally, I will maintain my reputation in the EUV lithography industry (and procure industrial funding) through projects involving the fabrication and hydrogen blistering of EUV mirrors. A thermal method will be used to measure sputtered neutral atom energies in order to tailor deposition conditions for smooth interfaces in alternating nanolayers of Mo and Si, and an ion gun and radical source will be used to investigate hydrogen blistering of these nanolayered structures.

Teaching Interests:

My pursuit of an academic career stems from a twin desire to pursue excellent research and to teach science in a way that maximizes its accessibility and prepares the next generation for success. Over the course of my time as both a student and a teacher, I came to the conclusion that the unifying link between effective teaching in all styles is: structure. The professor must understand the mindset of somebody without prior knowledge (and often without great interest in) the material, predict which directions such a mind will take, and structure the progression of the course to present the material in a manner that is logical to that mind. This is the approach I take in the classroom. As a graduate student at Illinois, I actively sought out teaching opportunities even though I was fully funded through my research. I taught gratis every year and was eventually listed as Co-Instructor for the course NPRE 101, “Introduction to Energy Systems”. Even as an undergraduate, I was deeply interested in teaching and pedagogy, choosing to attend Olin College because of its commitment to reinvent engineering education and emphasize hands-on project-based learning.

My interdisciplinary background has given me the experience necessary to teach a wide variety of subjects. Additionally, I would be very interested in creating plasma courses, such as a course on plasma processing and plasma chemistry. Topics covered could include ambipolar diffusion, conservation equations, collisional processes, reaction rates, plasma chemistry modeling, plasma-surface interactions, sputtering, etching, and various types of plasma sources and their applications. Because of my commitment to preparing students for real-world applications of science, I especially appreciate the kind of hands-on experience that a lab class can give, and I would like to create a plasma lab course that would serve as an introduction for anybody looking to perform experimental plasma work.

Postdoctoral Research: Selective Diagnostics for Plasma-Liquid Interactions in Plasma Biomedicine

Supervisor: Prof. David B. Graves; Chemical & Biomolecular Engineering; University of California, Berkeley

At Berkeley, I have focused mainly on the area of plasma-liquid interactions, which are crucial for plasma biomedicine, since medical effects of plasmas are caused largely by plasma-produced reactive oxygen and nitrogen species dissolved in biological liquids. During my postdoctoral work, I used a spin trap to selectively isolate trends due to plasma-produced O atoms dissolved in water. O atoms are very important for plasma-induced reactions in biological material, and this was the first time their effect had been separated out from those of other plasma-produced species in the aqueous phase. Current research involves the use of gas and liquid-phase diagnostics to quantify the improvement of plasma-liquid interactions in a perfluorocarbon solvent. Additionally, I have also worked on both hardware and software for a project on advanced control of atmospheric pressure plasmas. Advanced control is necessary in order to provide reliable plasma treatments on living subjects.

PhD Research: Removal of Tin from Extreme Ultraviolet Collector Optics by an In-Situ Hydrogen Plasma

Advisor: Prof. David N. Ruzic; Nuclear, Plasma, and Radiological Engineering; University of Illinois

At Illinois, I developed, measured, and simulated plasma techniques for the extreme ultraviolet (EUV) lithography industry. EUV lithography sources enable enhanced resolution and the continuation of Moore’s law by creating 13.5nm photons (an order of magnitude lower wavelength than currently-used 193nm photons) with high-energy Sn plasmas. The main factor now preventing high-volume commercial implementation is the fact that the Sn plasma debris can sputter, implant in, or deposit on the collector optic that focuses the EUV light. High-energy debris must be slowed down or deflected, and deposited Sn must be removed without turning the source off. My research provided multiple advances towards mitigating collector contamination. Important contributions include: (1) Demonstration of EUV reflectivity restoration by an in-situ technique to remove Sn from EUV collector optics with an H₂ plasma, (2) Isolation of ion energy flux as the main factor limiting the etch rate, (3) Exploitation of ion bombardment to achieve per-radical etching efficiencies orders of magnitude higher than those reported with traditional atomic H sources, (4) Demonstration of the fact that, contrary to previous thought, the unstable etch product SnH₄ does not significantly reduce etch rates by decomposing, and (5) Successful deflection of keV-range ions from a z-pinch EUV source with magnetic fields. This research was partially funded by an NSF GOALI grant which I co-authored.

Awards & Honors:

• Mavis Future Faculty Fellowship
• Co-Author of Successful NSF GOALI Proposal #14-36081: “In-Situ Plasma Cleaning of Optics: Building a Fundamental Understanding of the Etch Process in a Complex Plasma Environment”
• International EUVL Symposium Student Scholarship (2014, 2015)

Selected Publications:

• (Submitted) D.T. Elg, I. Yang, D.B. Graves, “Production of TEMPO by O Atoms in Atmospheric Pressure Non-Thermal Plasma-Liquid Interactions”, Journal of Physics D: Applied Physics (2017).
• D.T. Elg, G.A. Panici, S. Liu, G. Girolami, S.N. Srivastava, D.N. Ruzic, “Removal of Tin from Extreme Ultraviolet Collector Optics by Etching with an In-Situ Hydrogen Plasma”, Plasma Chemistry & Plasma Processing (2017).

1. Yang, K. Kalathiparambil, D.T. Elg, D.N. Ruzic, W.M. Kriven, “Microstructural Damage of α-Al₂O₃ by High Energy Density Plasma”, Acta Materialia 132, 479-490 (2016).

• D.T. Elg, G.A. Panici, J.S. Peck, S.N. Srivastava, D.N. Ruzic, “Modeling and Measurement of Hydrogen Radical Densities of In-Situ Plasma-Based Sn Cleaning Source”, Journal of Micro/Nanolithography, MEMS, & MOEMS 16(2) (2016).
• D.T. Elg, J.R. Sporre, G.A. Panici, S.N. Srivastava, D.N. Ruzic, “In-Situ Collector Cleaning and EUV Reflectivity Restoration by Hydrogen Plasma for EUV Sources”, Journal of Vacuum Science & Technology A 34(2) (2016).
• J.R. Sporre, D.T. Elg, Kishor K. Kalathiparambil, D.N. Ruzic, “Modeling and Measuring the Transport and Scattering of Energetic Debris in an EUV Plasma Source”, Journal of Micro/Nanolithography, MEMS, & MOEMS 15(1) (2016).
• D.T. Elg, J.R. Sporre, D. Curreli, I.A. Shchelkanov, D.N. Ruzic, K.R. Umstadter., “Magnetic Debris Mitigation System for EUV Sources”, Journal of Micro/Nanolithography, MEMS, & MOEMS 14(1) (2015).

Contact:

Daniel Elg
D75 Tan Hall
University of California
Berkeley, CA 94720
(630) 272-8503
daniel.elg@berkeley.edu