Research

Plasma Controls' research is presently focused on thermoelectric generator material development, plasma diagnostic development, and biomaterial surface modification.

Thermoelectric devices convert temperature gradients to electrical energy and vice versa. When a temperature gradient is applied across an n-type (excess electrons) and p-type (excess holes) material, the electrons and holes at the hot side diffuse toward the cold side, creating a voltage difference. If a circuit is attached, the movement of the charge carriers can perform work. Alternatively, an external power supply can be used to operate the device in reverse as a Peltier cooler, driving heat from the cold side to the hot side.

Generally, thermoelectric device efficiencies are far lower than that of “heat engines” that operate on Rankine or Sterling cycles for example. However, thermoelectrics are solid state devices with no moving parts and are thus are attractive at the milli/micro-watt power levels where standard conversion technologies are difficult to scale down in size. Thermoelectric devices show promise for waste-heat recovery in automobiles and cook stoves, and in air-conditioning to replace harmful refrigerants.

Research in thermoelectrics centers around improving the n- and p-type material’s figure of merit zT, which indicates the maximum device efficiency. Devices with figures of merit of 0.7 are available today, but this needs to be improved to make thermoelectrics competitive in more areas. Plasma Controls is interested in applying plasma techniques to thermoelectric device fabrication.

• G. Jeffrey Snyder and Eric S. Toberer,“Complex thermoelectric materials,” Nature Materials, Vol. 7, Feb. 2008.
• Cronin B. Vining, “An inconvenient truth about thermoelectrics,” Nature Materials, Vol. 8, Feb. 2009.

Plasma Controls has past experience with government agencies and private sector companies involved in electric propulsion research and development. Ion thruster research is a cornerstone of Plasma Controls history and experience. Both experimental and numerical tools are available to customers for ion thruster research.

Positioning systems are used with Langmuir, Emissive, Electrostatic Analyzer, ExB, and Retarding Potential Analyzer tools for experimental ion thruster and plasma source research.

Plasma Controls uses the ffx ion optics simulation tool for ion thruster grid development and research work. Additional numerical tools are available for the analysis of sputtered material deposition from target to substrate.

Plasma Controls has noteworthy experience working with direct-current (DC) filament or hollow cathode and radio-frequency (RF) electron bombardment ion sources. Ion sources are most commonly used in sputtering physical vapor deposition processes. Plasma Controls can assist in the design, development, and analysis of ion sources using our experimental and numerical tools.

Hollow cathodes are electron sources used to routinely initiate, sustain, and neutralize plasmas. Hollow cathodes can be used as plasma contactors on spacecraft to reduce potential differences and inhibit potentially damaging electric arcs. Hollow cathodes can be used in several gas environments and are a long-life alternative to filament cathodes.

Plasma Controls can provide near-cathode measurements of plasma potential, electron temperature, and electron density using several diagnostic methods. We investigate both low and high current hollow cathodes.

Plasma Controls uses the ffx ion optics simulation code for ion source grid design. The ffx code provides perveance, crossover, electron backstreaming, and grid lifetime predictions. Simulations are done in 3-D and can be performed on two, three, or four grid systems.

Plasma Controls can model sputter redeposition using its Surface Evolve simulation code. The code can model both stationary and rotational substrates in complex chamber geometries.

Plasma processing, including both physical vapor deposition (sputtering, ion implantation & deposition) and chemical vapor deposition (metal organic), can be used to improve the biocompatibility and active integration of biomaterials through surface engineering, i.e. the control of surface chemistry and topography through surface treatments and coatings. Plasma Controls is interested in developing plasma-based processes and systems that address identified drawbacks and limitations of current processing methods and materials.

Copper indium gallium diselenide (CIGS) and cadmium telluride (CdTe) photovoltaics are expected to be the two most cost competitive thin film solar technologies. With respect to CIGS solar cells, the Department of Energy solar energies technology program has set 95% yield, 10-15% efficiency, and $3 per watt installed cost targets by 2015. Careful process controls and diagnostic tools are needed to meet these yield, efficiency, and cost goals. Plasma Controls is interested in using its diagnostic tools and experience to develop new monitoring technologies that facilitate product development and the transition from laboratory to commercial scale device manufacturing.