Joshua Ryan Smith

Summary

I have expertise in developing physics-based models of physical systems and developing the software to implement them. In the past, I have worked on nanolithography using a scanning tunneling microscope as a stylus, and surface science including x-ray photoemission spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction.

I study energy conversion devices based on wide-bandgap semiconductors, specifically the III-nitrides. I am particularly interested in thermoelectron emission and energy conversion (sometimes called thermionic emission).

Experience

US Army Research Laboratory - ORAU Senior Researcher, Sensors and Electron Devices Directorate (August 2011 - Present).

At ARL I have investigated radioisotope batteries, namely betavoltaic and betaphotovoltaic devices. Our team demonstrated a working GaN based betavoltaic device -- I specified the structure, verified the devices using electron beam induced current scanning tunneling microscopy, and guided the devices through the various fabrication and characterization steps. For the betaphotovoltaic part of the project, I specified the AlGaN photovoltaic structure and developed a process of electrophoretic deposition to apply phosphor to the photovoltaic devices post-fabrication.

In addition to the radioisotope batteries, I developed a model of electron transport through a thermoelectron energy conversion device featuring a negative electron affinity anode. The software I wrote for this project is used by university research groups and a startup company. This work was recognized by ARL as well as the official homepage of the US Army.

Carnegie Mellon University - Postdoctoral Researcher, Prof. Robert Davis (June 2008 - July 2011).

At CMU I was the lead postdoc on a project to develop a nanolithography technique using a scanning tunneling microscope tip as a stylus. During this time I built the TFAN nanolithography/surface science laboratory from scratch. This lab featured an ultrahigh vacuum surface analysis system including in-situ sample preparation, scanning probe microscopy, x-ray photoemission spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction. I managed three graduate students and we developed processes to clean and hydrogen passivate Si (100), write features in the hydrogen passivation with the scanning probe tip, and adsorb disilane to the features.

NC State University - Graduate Research Assistant, Profs. Robert J. Nemanich and Griff L. Bilbro (August 2002 - August 2007).

At NCSU I investigated thermionic energy conversion devices based on diamond electrodes. I developed a comprehensive model of electron transport through the device which could account for emission from a diamond cathode featuring negative electron affinity. I implemented the model initially in MATLAB and later refactored in python. I also investigated negative electron affinity amorphous carbon films for the Interstellar Boundary Explorer (IBEX) mission in collaboration with Lockheed Martin. I developed a hydrogen passivation process for the amorphous carbon films and characterized the negative electron affinity with ultraviolet photoemission spectroscopy. I applied this process to amorphous carbon facets which were used as part of the IBEX-Lo detector. The IBEX space probe was launched October 19, 2008.

NC State University - Undergraduate Researcher, Prof. Lubos Mitas (August 2001 - May 2002).

Monte Carlo computational molecular dynamics.

NC State University - Research Experience for Undergraduates Program, Prof. Lubos Mitas (May 2001 - August 2001).

Monte Carlo computational molecular dynamics

Physics Tutorial Center, NC State University - Tutor (August 1998 - May 2000).

Triangle Learning Consultants, Raleigh, NC - Tutor (August 2000 - August 2002).

High school mathematics tutoring.

Johnson Controls, Charlotte, NC - Engineering Assistant (Summer 1999, Summer 2000).

AutoCAD

Education

  • Ph.D. Physics, NC State University, 2007
  • B.S. Physics, Cum Laude, NC State University, 2002
  • B.S. Mathematics, Cum Laude, NC State University, 2002
  • High School North Carolina School of Science and Mathematics, 1998

Skills and capabilities

My specialty is developing mathematical models of physical systems and implementing them in software using industry-standard software development practices. I have experience with the version control systems subversion and git, the programming languages python and MATLAB, SQLite databases, continuous integration with Travis-CI, and project management with GitHub. I regularly use and administer GNU/Linux (Ubuntu and RHEL) and OSX. I also have extensive experience with experimental surface science, ultrahigh vacuum equipment, and laboratory operations.

Teaching

Honors and Awards

  • COMAP Mathematical Contest in Modeling 2002, Meritorious Submission
  • Eagle Scout Award, 1996

Professional Affiliations

  • Member, Materials Research Society
  • Member, American Physical Society

Service

  • President, Graduate Physics Student Association (GPSA). April 2005 - April 2006
  • University Graduate Student Assc. Representative. April 2003 - April 2005

Countries Visited

Canada, France, Georgia, Germany, Greece, Italy, Morocco, Netherlands, Poland, Portugal, Spain, Turkey, Ukraine.

Dissertation

Thermionic Energy Conversion and Particle Detection Using Diamond and Diamond-Like Carbon Surfaces

Committee: Robert J. Nemanich (co-chair), Griff Bilbro (co-chair), David Aspnes, Thomas Perl

Selected Software

  • tec - Utilities for simulating vacuum thermionic energy conversion devices.
  • ibei - Calculator for incomplete Bose-Einstein integral.

Publications

Tompkins, R.P., Smith, J.R., Kirchner, K.W., Jones, K.A., Leach, J.H., Udwary, K., Preble, E., Suvarna, P., Leathersich, J.M., Shahedipour-Sandvik, F. GaN Power Schottky Diodes with Drift Layers Grown on Four Substrates. Journal of Electronic Materials, 2014; 43 (4): 850-856

Smith, J.R. Increasing the efficiency of a thermionic engine using a negative electron affinity collector. Journal of Applied Physics, 2013; 114: 164514

Tompkins, R.P., Smith, J.R., Kirchner, K.W., Jones, K.A., Preble, E., Leach, J., Mulholland, G., Suvarna, P., Tungare, M., Shahedipour-Sandvik, F. GaN Power Schottky Diodes. ECS Transactions 2012; 45 (7): 17-25

Smith, J.R., Bilbro, G., Nemanich, R. Theory of space charge limited regime of thermionic energy converter with negative electron affinity emitter. Journal of Vacuum Science and Technology B, 2009; 27: 1132-1141

Smith, J.R., Bilbro, G., Nemanich, R. Considerations for a high performance thermionic energy conversion device based on an NEA emitter. Physical Review B, 2007; 76: 245327-245332

Smith, J.R., Bilbro, G., Nemanich, R. Using negative electron affinity diamond emitters to mitigate space charge in vacuum thermionic energy conversion devices. Diamond and Related Materials, 2006; 15: 2082-2085.

Smith, J.R., Bilbro, G., Nemanich, R. The effect of Schottky barrier lowering and nonplanar emitter geometry on the performance of a thermionic energy converter. Diamond and Related Materials, 2006; 15: 870-874.

Smith, R.C., Seelecke, S., Ounaies, Z., Smith, J.R. A Free Energy Model for Hysteresis in Ferroelectric Materials. Journal of Intelligent Material Systems and Structures, Nov 2003; 14: 719 - 739.

Smith, R.C., Salapaka, M.V., Hatch, A., Smith, J.R., De, T. Model Development and Inverse Compensator Design for High Speed Nanopositioning. Proceedings of the 41st IEEE Conference on Decision and Control, 2002.Volume: 4,10-13 Dec. 2002 Pages:3652 - 3657 vol.4

Non-refereed Publications

Khan, M.R., Smith, J.R., Kirchner, K., Jones, K.A. Applying LaPO4 Phosphor via Spinning for BetaPhotovoltaic Devices. US Army Research Laboratory Technical Report ARL-TR-7269, June 2015

Invited Presentations

Smith, J.R. September 2015. Achieving >20% efficiency using a vacuum thermionic energy converter featuring a diamond anode. University of British Columbia.

Presentations

Smith, J.R. November 2013. Achieving >20% efficiency using a vacuum thermionic energy converter featuring a III-nitride, negative electron affinity anode. Materials Research Society Fall Meeting, Boston, Massachusetts.

Smith, J.R., Ricketts, D., Bain, J. June 2011. Localized Thermal Modification of Surfaces via Electron Bombardment from an STM Tip. 55th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication, Las Vegas, Nevada.

Smith, J.R., Ricketts, D., Hu, W., Dang, Y., Ozcan, O., Sitti, M., Davis, R., Bain, J. November 2010. Scanning Probe Nanomanufacturing on Si: Surface Characterization of the Process Technique. Materials Research Society Fall Meeting, Boston, Massachusetts.

Smith, J.R., Bilbro, G., Nemanich, R. March 2009. Optimized vacuum thermionic energy conversion using diamond materials. American Physical Society March Meeting, Pittsburgh, Pennsylvania.

Smith, J.R., Bilbro, G., Nemanich, R. November 2007. Vacuum thermionic energy conversion from nitrogen and phosphorus doped diamond. Materials Research Society Fall Meeting, Boston, Massachusetts.

Smith, J.R., Nemanich, R., Friedmann, T., Hertzberg, E. November 2007. Development of a Hydrogen Termination Procedure for Tetrahedral Amorphous Carbon for use with the Interstellar Boundary Explorer. Materials Research Society Fall Meeting, Boston, Massachusetts.

Smith, J.R., Bilbro, G., Nemanich, R. September 2007. Efficient conversion of heat directly to electricity using negative electron affinity diamond electrodes. 18th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, and Nitrides 2007. Berlin, Germany.

Smith, J.R., Bilbro, G., Nemanich, R. March 2007. Theoretical investigation of vacuum thermionic energy conversion devices for efficient conversion of solar to electrical energy. American Physical Society March Meeting, Denver, Colorado.

Smith, J.R., Bilbro, G., Nemanich, R. May 2006. The Effect of Negative Electron Affinity Emitters on the Space Charge Effect of Vacuum Thermionic Energy Conversion Devices. ICNDST & ADC 2006 Joint Conference, Research Triangle Park, North Carolina.

Smith, J.R., Bilbro, G., Nemanich, R. March 2006. The Effect of Negative Electron Affinity Emitter Materials on Space Charge Mitigation of Vacuum Thermionic Energy Conversion Devices. American Physical Society March Meeting, Baltimore, Maryland.

Smith, J.R., Bilbro, G., Nemanich, R. December 2005. Vacuum TEC Modeling. Thermionic Energy Conversion MURI Review Meeting. Berkeley, California.

Smith, J.R., Bilbro, G., Nemanich, R. November 2005. Effect of Nanostructured Emitters on the Performance of Vacuum Thermionic Energy Conversion Devices. Materials Research Society Fall Meeting, Boston, Massachusetts.

Smith, J.R., Bilbro, G., Nemanich, R. December 2004. Modeling Vacuum Thermionic Energy Converters. Thermionic Energy Conversion MURI Review Meeting. Santa Cruz, California.

Smith, J.R., Bilbro, G., Nemanich, R. July 2004. Modeling Vacuum Thermionic Energy Converters. Thermionic Energy Conversion MURI Review Meeting, Raleigh, North Carolina.

Smith, J.R., Bilbro, G., Nemanich, R. April 2004. The Theory of Thermionic Energy Conversion. Thermioinic Energy Conversion SBIR phase II Kickoff meeting, Raleigh, North Carolina.

Smith, J.R. and Mitas, L. 2001. Molecular Dynamics Simulations. 2001 Summer REU Program Presentations, Raleigh, North Carolina.

Posters

Smith, J.R. November 2014. Beta-enhanced thermoelectron emission and energy conversion, Boston, MA.

Smith, J.R. August 2013. Simulated thermionic engine performance using III-nitride, negative electron affinity collector, Washington, DC.

Smith, J.R., Ricketts, D., Davis, R., Bain, J., Fedder, G., Sitti, M., Santhanam, S., Dang, Y., Hu, W., Ozcan, O., Zhang, A., Gu, J. Tip directed, field assisted nanomanufacturing. DARPA MEMS PI Review Meeting July 2010. San Francisco, California.

Smith, J.R., Hu, W., Dang, Y., Ozcan, O., Sitti, M., Bain, J., Davis, R., Ricketts, D. Towards Writing Si Nanowires on Si (100) with an STM Tip: Surface Preparation and Initial Results. Materials Research Society Fall Meeting 2009. Boston, Massachusetts.

Smith, J.R., Ricketts, D., Davis, R., Bain, J., Fedder, G., Sitti, M., Santhanam, S., Dang, Y., Hu, W., Ozcan, O., Zhang, A. Tip directed, field assisted nanomanufacturing: Initial surface preparation results. DARPA MEMS PI Review Meeting July 2009. Sunriver, Oregon.

Smith, J.R., Nemanich, R. Hertzberg, E., Friedmann, T.A. Hydrogen termination of ta:C for use in interstellar neutral particle detection. New Diamond and Nano Carbons 2007. Osaka, Japan.

Smith, J.R., Nemanich, R. Effect of Hydrogen Passivation on RMS Roughness and Electronic Structure of Diamond-like Carbon Films. Materials Research Society Fall Meeting 2006. Boston, Massachusetts.

Smith, J.R., Bilbro, G., Nemanich, R. Theory of the performance of a thermionic energy conversion device with a negative electron affinity emitter. 17th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, and Nitrides 2006. Estoril, Portugal.

Smith, J.R., Bilbro, G., Nemanich, R. A model for the effect of Schottky barrier lowering and non-planar emitter geometry on the performance of a thermionic energy converter. 16th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, and Nitrides 2005. Toulouse, France.

Smith, J.R., Bilbro, G., Nemanich, R. Modeling Thermionic Energy Conversion Devices. June 2005 Thermionic Energy Conversion MURI Meeting, Santa Barbara, California.

Smith, J.R. and Bilbro, G. Conventional Theory of Thermioinic Emission. November 2003. Thermionic Energy Conversion MURI Review Meeting, Cambridge, Massachusetts.