Sandia Labs FY21 LDRD Annual Report

FY21 ANNUAL REPORT

Dissipating advanced satellite systems heat load with a new thermal interface material. The problematic heat load from advanced satellite systems with focal-plane array sensors, central processing units, and graphics processing units continues to increase. Existing thermal interface materials (TIM) limit operational performance and/or require high power cryocoolers to achieve desired operating temperatures. With thermal conductivities potentially 10x greater than metals, arrays of vertically- aligned carbon nanotubes (CNT) could greatly reduce thermal resistances. This LDRD project team built on previous LDRD projects and focused on growing high quality, vertically aligned CNTs in high packing fractions on thermally-conductive substrates to optimize overall TIM conductivity. Sandia also collaborated with Georgia Tech and Carbice TM to measure the thermal cooling properties from CNT arrays they developed on a thermally-conductive adhesive substrates approved for use by NASA. Considering

the superior CNT quality and array geometry of Sandia’s materials, researchers anticipate even greater advantages for CNT- TIM applications. (PI: Mike Siegal) (a) Vertically-aligned CNT array grown via nanopore template method resulting in > 40% volumetric fill factor. (b) Nanowires dried in supercritical CO 2 to prevent agglomeration.

(a)

(b)

Using atomic precision advanced manufacturing to unlock computing hardware functionality. Unlocking inaccessible computing hardware functionality is the focus of the Far-reaching Application, Implication, and Realization of Digital Electronics at the Atomic Limit (FAIR DEAL) Grand Challenge project. The LDRD team developed the science and technology required to use atomic precision advanced manufacturing (APAM) to meet their objective. APAM uses surface chemistry to introduce dopants into silicon at a density that exceeds the solid solubility limit and with sub-nanometer precision, and this technique may be used to improve the energy efficiency of microelectronics by leveraging new physical effects. The team fabricated the first complicated transistor devices based on APAM that works at room temperature and also expanded the applicability of APAM by developing an APAM acceptor chemistry, an APAM oxide chemistry, a route to image reversal, and two paths to high throughput fabrication. A

foundational achievement came through direct integration of APAM with complimentary metal- oxide semiconductor (CMOS) and identifying a near- term application in improving state-of-the-art CMOS metal-semiconductor contacts. (PI: Shashank Misra)

Tunnel field effect transistors are predicted to improve the energy efficiency of microelectronics by 10x, which APAM is helping to realize in practice.

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LABORATORY DIRECTED RESEARCH & DEVELOPMENT