hu.seas.ucla.eduHu Research Lab - University of California, Los Angeles

HOME RESEARCH PEOPLE PUBLICATIONS FACILITIES NEWS OPEN POSITIONS CONTACT Welcome! The H-Lab is a research group in the School of Engineering and Applied Science at UCLA, led by Professor Yongjie Hu. Motivated by technological challenges, our lab's research focus is on understanding and engineering nanoscale transport phenomena and nanomaterials for wide applications including energy, electronics, thermal management, and micro/nano sensors. We use a variety of experimental and theoretical techniques to investigate nanoscale transport processes, with a particular emphasis on design and chemical synthesis of advanced materials, ultrafast optical spectroscopy, pulsed electronics, and thermal spectral mapping techniques. We invite you to look at the website for more details about our work and facilities. News Yongjie received the 2019 Bergles-Rohsenow Young Investigator Award in Heat transfer. Thanks for the recognition by ASME! Nov 12, 2019 We developed an experimental database that reports systematically the optical, mechanical, and thermal properties of cubic boron arsenide. The work was published and featured in Appl. Phys. Lett. Also see the APL Scilight. Sept 16, 2019 Hang, Huan, and Lucas' theory work on "Ab initio investigation of single-layer high thermal conductivity boron compounds" was published in Phys. Rev. B. July 24, 2019 Joon and Huan's work on investigating the intrinsic ultralow thermal conductivity and phonon renormalization due to strong anharmonicity of tin selenide is published in Nano Letters. July 2, 2019 Man's work on studying interface energy transport and anisotropic thermal boundary resistance for near-junction thermal management was published in Advanced Materials. June 24, 2019 Yongjie is selected to participate in the National Academy of Engineering's 2019 U.S. Frontiers of Engineering. June 1, 2019 Our work was published on developing a facile ambient process for manufacturing ultralight, flexible, and superhydrophobic thermal insulator. May 27, 2019 H-Lab student Joon Sang Kang has been awarded the Gold medal for this year's MRS Graduate Student Award for his outstanding PhD research. Congratulations! April 30, 2019 Yongjie is selected as 2019 Alfred P. Sloan Research Fellow! Many thanks for the honor and support from Sloan Foundation! Feb 19, 2019 Huu's work on developing nanoscale sensors and systems beyond solid state electronics was published online: high-performance emitter for nanoscale vacuum channel transistors. Jan 22, 2019 Nicolas's work was accepted for publication, demonstrating flexible thin film devices to recover lower-grade waste heat and power electronics and sensors. Jan 21, 2019 Our group developed a new metrology for anisotropic thermal conductivity measurement. Man and Joon's new technique using an elliptical laser beam, i.e., AB-TDTR was published in Rev. Sci. Instruments. Aug 2, 2018 Our group's study on developing high thermal conductivity boron arsenide was published in Science magzine! This is a highly interdisciplinary project that requires precise materials synthesis, comprehensive structural characterizations, accurate thermal transport measurement, and atomistic ab-initio calculations: Congratulations and thank H-Lab students for the hard work to get it done! See UCLA news here. July 05, 2018 Yongjie received 2018 UCLA Faculty Career Development Award. June 21, 2018 Congrationlations to H-Lab student, Joon Sang Kang, for receiving UCLA Northrop Grumman Corporation Scholarship, for his outstanding graduate research! April 16, 2018 Yongjie received NSF CAREER Award! Many thanks for the support from the National Science Foundation!! Feb 21, 2018 Congratulations to H-Lab students, Joon and Huan for passing their PhD Qualifying Exams! Dec 18, 2017 Congratulations on Joon and Huan's paper published in Nano Letters : Thermal and phonon spectral characterization for energy-efficient thermal management! Nov 8, 2017 Congratulations to H-Lab students: Huan, Huu, Man, and Nicolas for all passing their PhD Candidacy Exam! July 18, 2017 Yongjie received the Doctoral New Investigator Award from the American Chemical Society (ACS)! Many thanks for the support from ACS PRF!! June 23, 2017 New paper on high-performance flexible thin film thermoelectric devices published in Advanced Materials . March 29, 2017 Congratulations on Joon and Ming's paper published in Nano Letters ! This is the first time demonstration of in situ thermal-electrochemical characterization of a 2D van der Waals material based lithium ion battery. Feb 23, 2017 Our team is awarded a competitive research grant as part of UCLA Sustainable LA Grand Challenge! Many thanks to the Sustainable LA Grand Challenge and the Anthony and Jeanne Pritzker Family Foundation!! Dec 21, 2016 Yongjie has received the Air Force Young Investigator Award! Many thanks for the support from AFOSR!! Oct 12, 2016 Welcome new graduate students joining our lab: Nicolas, Man, Julia, Junyu, Huu, Huan! Sept 15, 2016 Electrical-gate tuning of thermoelectric transport in single heterostructure nanowires is published on J. Appl. Phys. . June 15, 2016 We have received a grant support from the US Department of Energy, together with Professors Pilon, Dunn, and Tolbert. We very much appreciate the generous support from DOE! May 20, 2016 Developing a refined technique to measure phonon mean free path distributions is published on Scientific Reports . Nov 27, 2015 Manuscript posted on arXiv : No energy transport without discord: Quantum correlations are mandatory for any energy transport. Oct 16, 2015 Congratulations for the new paper published on Nature Nanotechnology : spectral mapping of thermal conductivity through nanoscale ballistic heat transfer! June 10th, 2015 Congratulations to Joon for passing his PhD Candidacy Exam! May 15, 2015 Developing ultra-high thermal condutivity material - Boron Arsenide, is published on Appl. Phys. Lett.: the first experimental measurement on its thermal conductivity. Feb 20, 2015 Spotlight more -- Intrinsic low thermal conductivity and phonon renormalization due to strong anharmonicity of single-crystal tin selenide This study reports the experimental measurements and theoretical calculations of phonon transport in the record-high thermoelectric material, i.e. SnSe but focuses on its undoped and fully dense single crystals. To investigate the phonon anharmonicty, we developed experimental approach combining picosecond ultrasonics and X-ray diffraction, to enable direct measurement of temperature-dependent sound velocity, thermal expansion coefficient, and Gruneisen parameter. The measured Gruneisen parameter suggests an abnormally large temperature effect on phonon dispersion that contributes to over 90% of phonon frequency shifts. Furthermore, we performed ab initio calculations using different methods: in comparison with self-consistent phonon theory, the harmonic and quasi-harmonic models that have been widely used in current phonon calculations, fail to accurately predict these important thermophysical properties. Our study reveals an extremely strong intrinsic anharmonicity in SnSe that introduces phonon renormalization near room temperature. This study represents an important research benchmark in characterizing high-performance thermal energy materials, and provides fundamental insight into advancing modern calculation methods for phonon transport theory. July 4, 2019 Observation of anisotropic thermal boundary resistance for near-junction thermal management: experiment and atomistic modeling of interfacial energy transport Interfacial thermal boundary resistance (TBR) plays a critical role in near-junction thermal management of modern electronics. In particular, TBR can dominate heat dissipation and has become increasingly important due to the continuous emergence of novel nanomaterials with promising electronic and thermal applications. A highly anisotropic TBR across a prototype 2D material, i.e., black phosphorus, is reported th...