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Início Arquivos Thermal Letter Representantes Futuras reuniões Assembléia das Conferências Internacionais de Transferência de Calor
International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

PROBING LOCAL THERMAL CONDUCTIVITY VARIATIONS IN CVD DIAMOND WITH LARGE GRAINS BY TIME-DOMAIN THERMOREFLECTANCE

Zhe Cheng
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Ramez Cheaito
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA

Tingyu Bai
Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 91355, USA

Luke Yates
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Aditya Sood
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA

Brian M. Foley
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Thomas L. Bougher
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Firooz Faili
Element Six Technologies, Santa Clara, CA 95054, USA

Mehdi Asheghi
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA

Kenneth E. Goodson
Thermosciences Division, Mechanical Engineering Department, Stanford University Bldg. 530, 440 Escondido Mall, Stanford, CA 94305-3030, USA

Baratunde A. Cola
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Mark Goorsky
Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 91355, USA

Samuel Graham
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

DOI: 10.1615/IHTC16.tpm.022782
pages 8694-8701


Palavras-chave: Electronic equipment cooling, Nano/Micro scale measurement and simulation, GaN on diamond, anisotropic thermal conductivity, thermal conductivity mapping, TDTR

Resumo

Chemical vapor deposited (CVD) diamond, due to its high thermal conductivity, is an attractive candidate for thermal management of GaN-based high-electron mobility transistors (HEMTs). However, because of its heterogeneous grain structure, CVD diamond has a spatially inhomogeneous thermal conductivity at the microscale. To understand this inhomogeneity and the effect of structural imperfections on thermal conduction, time-domain thermoreflectance (TDTR) is used to study the local thermal conductivity of two samples: a heavily boron-doped ~534 μm-thick diamond sample with an average surface grain size of ~23 μm, and an undoped diamond sample that was cut from a bulk piece of CVD diamond. For the doped diamond, large thermal conductivity variations (of nearly 50 %) are observed across the surface of the sample. For the undoped sample, the large average grain size (several hundred ?m) results in a high local thermal conductivity (>2000 W/m-K, close to the conductivity of bulk diamond). The thermal conductivity is not seen to change significantly with grain size (127 - 260 μm), and we measure up to ~8 % variation in the local thermal conductivity. We speculate that grain boundary scattering affects phonon transport differently in the two samples, possibly due to varying amounts of near-boundary disorder. This work provides insights to understand the local thermal conductivity inhomogeneity and phonon transport across grain boundaries in CVD diamond with large grains, which is important for thermal management applications in high-power electronics.

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