All Publications


  • Thermal and Manufacturing Design Considerations for Silicon-Based Embedded Microchannel-Three-Dimensional Manifold Coolers-Part 2: Parametric Study of EMMCs for High Heat Flux (similar to 1kW/cm(2)) Power Electronics Cooling Jung, K., Hazra, S., Kwon, H., Piazza, A., Jih, E., Asheghi, M., Gupta, M., Degner, M., Goodson, K. E. ASME. 2020

    View details for DOI 10.1115/1.4047883

    View details for Web of Science ID 000576282500019

  • Tungsten-doped Ge2Sb2Te5 phase change material for high-speed optical switching devices APPLIED PHYSICS LETTERS Guo, P., Burrow, J. A., Sevison, G. A., Kwon, H., Perez, C., Hendrickson, J. R., Smith, E. M., Asheghi, M., Goodson, K. E., Agha, I., Sarangan, A. M. 2020; 116 (13)

    View details for DOI 10.1063/1.5142552

    View details for Web of Science ID 000524534800001

  • Phase Change Dynamics and Two-Dimensional 4-Bit Memory in Ge2Sb2Te5 via Telecom-Band Encoding ACS PHOTONICS Sevison, G. A., Farzinazar, S., Burrow, J. A., Perez, C., Kwon, H., Lee, J., Asheghi, M., Goodson, K. E., Sarangan, A., Hendrickson, J. R., Agha, I. 2020; 7 (2): 480–87
  • Tunable Dielectric and Thermal Properties of Oxide Dielectrics via Substrate Biasing in Plasma-Enhanced Atomic Layer Deposition. ACS applied materials & interfaces Kim, Y. n., Kwon, H. n., Han, H. S., Kim, H. J., Kim, B. S., Lee, B. C., Lee, J. n., Asheghi, M. n., Prinz, F. B., Goodson, K. E., Lim, J. n., Sim, U. n., Park, W. n. 2020

    Abstract

    The ability to control the properties of dielectric thin films on demand is of fundamental interest in nanoscale devices. Here, we modulate plasma characteristics at the surface of a substrate to tune both dielectric constant and thermal conductivity of amorphous thin films grown using plasma-enhanced atomic layer deposition. Specifically, we apply a substrate bias ranging from 0 to ∼117 V and demonstrate the systematic tunability of various material parameters of Al2O3. As a function of the substrate bias, we find a nonmonotonical evolution of intrinsic properties, including density, dielectric constant, and thermal conductivity. A key observation is that the maximum values in dielectric constant and effective thermal conductivity emerge at different substrate biases. The impact of density on both thermal conductivity and dielectric constant is further examined using a differential effective medium theory and the Clausius-Mossotti model, respectively. We find that the peak value in the dielectric constant deviates from the Clausius-Mossotti model, indicating the change of oxygen fraction in our thin films as a function of substrate bias. This finding suggests that the increased local strength of plasma sheath not only enhances material density but also controls the dynamics of microstructural defect formation beyond what is possible with conventional approaches. Based on our experimental observations and modeling, we further build a phenomenological relation between dielectric constant and thermal conductivity. Our results pave invaluable avenues for optimizing dielectric thin films at the atomic scale for a wide range of applications in nanoelectronics and energy devices.

    View details for DOI 10.1021/acsami.0c11086

    View details for PubMedID 32915545

  • PARAMETRIC STUDY OF SILICON -BASED EMBEDDED MICROCHANNELS WITH 3D MANIFOLD COOLERS (EMMC) FOR HIGH HEAT FLUX (-1 kW/cm2) POWER ELECTRONICS COOLING Jung, K., Hazra, S., Kwon, H., Piazza, A., Jih, E., Asheghi, M., Gupta, M., Degner, M., Goodson, K. E., ASME AMER SOC MECHANICAL ENGINEERS. 2020
  • Optical and electrical properties of phase change materials for high-speed optoelectronics Burrow, J. A., Guo, P., Sevison, G. A., Kwon, H., Perez, C., Asheghi, M., Hendrickson, J. R., Sarangan, A., Goodson, K. E., Agha, I., IEEE IEEE. 2019
  • Direct Visualization of Thermal Conductivity Suppression Due to Enhanced Phonon Scattering Near Individual Grain Boundaries. Nano letters Sood, A., Cheaito, R., Bai, T., Kwon, H., Wang, Y., Li, C., Yates, L., Bougher, T., Graham, S., Asheghi, M., Goorsky, M., Goodson, K. E. 2018

    Abstract

    Understanding the impact of lattice imperfections on nanoscale thermal transport is crucial for diverse applications ranging from thermal management to energy conversion. Grain boundaries (GBs) are ubiquitous defects in polycrystalline materials, which scatter phonons and reduce thermal conductivity (kappa). Historically, their impact on heat conduction has been studied indirectly through spatially averaged measurements, that provide little information about phonon transport near a single GB. Here, using spatially resolved time-domain thermoreflectance (TDTR) measurements in combination with electron backscatter diffraction (EBSD), we make localized measurements of kappa within few mum of individual GBs in boron-doped polycrystalline diamond. We observe strongly suppressed thermal transport near GBs, a reduction in kappa from 1000 W m-1 K-1 at the center of large grains to 400 W m-1 K-1 in the immediate vicinity of GBs. Furthermore, we show that this reduction in kappa is measured up to 10 mum away from a GB. A theoretical model is proposed that captures the local reduction in phonon mean-free-paths due to strongly diffuse phonon scattering at the disordered grain boundaries. Our results provide a new framework for understanding phonon-defect interactions in nanomaterials, with implications for the use of high-kappa polycrystalline materials as heat sinks in electronics thermal management.

    View details for PubMedID 29631399

  • HIGH STABILITY THERMAL ACCELEROMETER BASED ON ULTRATHIN PLATINUM ALD NANOSTRUCTURES Everhart, C. M., Kaplan, K. E., Winterkorn, M. M., Kwon, H., Provine, J., Asheghi, M., Goodson, K. E., Prinz, F. B., Kenny, T. W., IEEE IEEE. 2018: 976–79