Probing local thermal conductivity variations in CVD diamond with large grains by time-domain thermoreflectance

Zhe Cheng, Ramez Cheaito, Tingyu Bai, Luke Yates, Aditya Sood, Brian Foley, Thomas Bougher, Firooz Faili, Mehdi Asheghi, Kenneth Goodson, Baratunde A. Cola, Mark Goorsky, Samuel Graham

Research output: Contribution to journalConference article

Abstract

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 µm) 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.

Original languageEnglish (US)
Pages (from-to)8694-8701
Number of pages8
JournalInternational Heat Transfer Conference
Volume2018-August
StatePublished - Jan 1 2018
Event16th International Heat Transfer Conference, IHTC 2018 - Beijing, China
Duration: Aug 10 2018Aug 15 2018

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Diamond
Diamonds
Thermal conductivity
thermal conductivity
diamonds
Vapors
vapors
grain size
Temperature control
Grain boundaries
inhomogeneity
grain boundaries
Phonon scattering
Boron
Crystal microstructure
High electron mobility transistors
high electron mobility transistors
Power electronics
microbalances
boron

All Science Journal Classification (ASJC) codes

  • Fluid Flow and Transfer Processes
  • Condensed Matter Physics
  • Mechanical Engineering

Cite this

Cheng, Zhe ; Cheaito, Ramez ; Bai, Tingyu ; Yates, Luke ; Sood, Aditya ; Foley, Brian ; Bougher, Thomas ; Faili, Firooz ; Asheghi, Mehdi ; Goodson, Kenneth ; Cola, Baratunde A. ; Goorsky, Mark ; Graham, Samuel. / Probing local thermal conductivity variations in CVD diamond with large grains by time-domain thermoreflectance. In: International Heat Transfer Conference. 2018 ; Vol. 2018-August. pp. 8694-8701.
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abstract = "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 µm) 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.",
author = "Zhe Cheng and Ramez Cheaito and Tingyu Bai and Luke Yates and Aditya Sood and Brian Foley and Thomas Bougher and Firooz Faili and Mehdi Asheghi and Kenneth Goodson and Cola, {Baratunde A.} and Mark Goorsky and Samuel Graham",
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Cheng, Z, Cheaito, R, Bai, T, Yates, L, Sood, A, Foley, B, Bougher, T, Faili, F, Asheghi, M, Goodson, K, Cola, BA, Goorsky, M & Graham, S 2018, 'Probing local thermal conductivity variations in CVD diamond with large grains by time-domain thermoreflectance', International Heat Transfer Conference, vol. 2018-August, pp. 8694-8701.

Probing local thermal conductivity variations in CVD diamond with large grains by time-domain thermoreflectance. / Cheng, Zhe; Cheaito, Ramez; Bai, Tingyu; Yates, Luke; Sood, Aditya; Foley, Brian; Bougher, Thomas; Faili, Firooz; Asheghi, Mehdi; Goodson, Kenneth; Cola, Baratunde A.; Goorsky, Mark; Graham, Samuel.

In: International Heat Transfer Conference, Vol. 2018-August, 01.01.2018, p. 8694-8701.

Research output: Contribution to journalConference article

TY - JOUR

T1 - Probing local thermal conductivity variations in CVD diamond with large grains by time-domain thermoreflectance

AU - Cheng, Zhe

AU - Cheaito, Ramez

AU - Bai, Tingyu

AU - Yates, Luke

AU - Sood, Aditya

AU - Foley, Brian

AU - Bougher, Thomas

AU - Faili, Firooz

AU - Asheghi, Mehdi

AU - Goodson, Kenneth

AU - Cola, Baratunde A.

AU - Goorsky, Mark

AU - Graham, Samuel

PY - 2018/1/1

Y1 - 2018/1/1

N2 - 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 µm) 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.

AB - 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 µm) 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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M3 - Conference article

VL - 2018-August

SP - 8694

EP - 8701

JO - International Heat Transfer Conference

JF - International Heat Transfer Conference

SN - 2377-424X

ER -