THE UCLA POEM MISSION AND RESEARCH SCOPE

The mission of the UCLA Phonon Optimized Engineered Materials (UCLA POEM) Laboratory is the fundamental science investigation of phonons and phonon-related phenomena in advanced materials and the development of innovative methods for controlling phonon transport and phonon interactions with electrons and photons for future electronic and energy conversion technologies. Phonons are quanta of crystal lattice vibrations. Phonons affect materials’ electronic, thermal, optical, and magnetic properties. Acoustic phonons are the main heat carriers in semiconductor and electrically insulating materials. Optical phonons define many optical characteristics of materials. Together, acoustic and optical phonons, scatter electrons, limiting electron mobility and electron coherency in semiconductors. Phonons are essential for forming charge density wave condensate and superconductive phases. The field of phononics or phonon engineering comprises the detailed study and control of phonons, i.e. quanta of crystal lattice vibrations, whose characteristics influence the properties of bulk and nanostructured materials. Phononics of lower-dimensional material systems is particularly interesting, enabling one to elucidate the physics of crystal lattice vibrations and to engineer the phonon spectrum to achieve new properties and functionalities of the materials.

THE UCLA POEM LABORATORY ORGANIZATION

Balandin Group operates the Phonon Optimized Engineered Materials (UCLA POEM) Laboratory, which is located on the ground floor in the Engineering V building. The main POEM Lab hosts electrical, thermal, and low-frequency noise measurement equipment, glove boxes, and transfer systems for van der Waals materials, microscopy, and other equipment. The Raman and Brillouin – Mandelstam Spectroscopy Laboratory (SPECTRA Lab), part of the POEM Laboratory, is in a separate location on the group floor in the Engineering V building. The Cryogenic Brillouin – Mandelstam Spectroscopy (BMS) Facility is located on the ground floor of the California NanoSystems Institute (CNSI). The equipment for chemical exfoliation, processing, and composite preparation is located in the shared research space in the Engineering VI building. The photos below show the POEM MAIN LAB (Figure 1) and POEM SPECTRA LAB (Figure 2).

Figure 1: Views of the Phonon Optimized Engineered Materials (UCLA POEM) Laboratory. The main lab features state-of-the-art equipment that includes Quantum Design PPMS, an in-house-built electronic low-noise measurement setup based on the Lake Shore cryogenic system, a range of the Netzsch thermal measurement systems, advanced VTI Vacuum Technology glove boxes, in-house-built materials transfer systems, microscopes, and other equipment. UCLA POEM Laboratory, Department of Materials Science and Engineering, Engineering V Building, UCLA, December 2024.

Figure 2: Views of Raman and Brillouin – Mandelstam Spectroscopy Laboratory (SPECTRA LAB), a part of the Phonon Optimized Engineered Materials (UCLA POEM) Laboratory. The lab features state-of-the-art Renishaw INVIA and VIRSA systems and an in-house-built Brillouin spectrometer. SPECTRA LAB of the UCLA POEM Laboratory, Department of Materials Science and Engineering, Engineering V Building, UCLA, December 2024.

HIGHLIGHTS OF FUNDAMENTAL SCIENCE ACHIEVEMENTS

Phonon Engineering: In 1997, Dr. A. A. Balandin, as a postdoctoral researcher at UCLA, envisioned that by changing the spectrum of acoustic phonons in nanostructures via spatial confinement one can modify the interaction of phonons with defects and change the phonon thermal conductivity. Previously, in the context of thermal transport, the energy dispersion of acoustic phonons was assumed to be the same as in “bulk” semiconductors, even in free-standing nanostructures. The phonon–boundary scattering was the only nanoscale-related mechanism affecting the phonon heat conduction in nanostructures. His Phys. Rev. B (1998) was the first report that described the acoustic phonon confinement effect on thermal transport and introduced the term “phonon engineering” in a journal publication. It took years but eventually, the idea of the phonon wave interference effects became conventionally accepted. In 2016, Professor Balandin and his POEM laboratory team demonstrated experimentally the spatial confinement of acoustic phonons in individual semiconductor nanowires, proving that the acoustic phonon spectrum is strongly modified even in nanowires with relatively large diameters, and reported the findings in Nature Com. (2016). The phonon engineering concepts and approaches are now being incorporated into the design of devices to increase energy conversion efficiency, enhance electron mobility, improve heat removal, and tune the light-matter interactions. The phonon engineering concept became the mainstream research direction with practical applications. Professor Balandin was recognized for this work with the IEEE Pioneer in Nanotechnology Award (2011), a Fellow of IEEE, numerous plenary, keynote, and invited talks at the top conferences such as international biannual PHONONICS, flagship IEEE NANO, invited reviews in Materials Today, MRS Bulletin, and several U.S. patents granted in the nanophononics field.

Graphene Thermal Field: After the first exfoliation of graphene and electrical measurements in 2004, the research community has focused on the liner energy dispersion of electrons in graphene and its implications for electronic transport. In 2008, Professor Balandin went in an entirely different direction by conducting pioneering studies of the thermal properties of graphene. His first paper on the subject, Nano Letter (2008), has been cited more than 17,000 times. Following the experimental discovery that the thermal conductivity of graphene can be higher than that of the basal planes of graphite, he explained this non-trivial fact theoretically by the specifics of the 2D phonon transport in graphene in Nature Mat. (2010), Phys. Rev. B (2010) and Nature Mat. (2011). In 2011, expanding this research field to engineering applications, his group developed the first thermal interface materials (TIMs) with graphene and few-layer graphene. In later years, the Balandin Group demonstrated the application of graphene thermal technologies with computers, solar cells, and battery packs. The new optothermal method for measuring thermal conductivity, which Professor Balandin developed for graphene, has been extended to other 2D materials and adopted in many laboratories worldwide. The graphene thermal technologies have become the real large-scale practical application of graphene – one can now buy commercial thermal paste or epoxies with graphene fillers, or even sports jackets with graphene-enhanced textiles for better heat spreading. For these research achievements, Professor Balandin was recognized with The MRS Medal from the Materials Research Society, a Fellow of MRS, The Brillouin Medal, numerous plenary, keynote, and invited talks at the top conferences such as Graphene Week, MRS Fall and Spring Meetings, Nature Conference, invited reviews in Nature Mat., Reports on Progress in Physics, and ACS Nano, a feature article in IEEE Spectrum and other magazines. He received several U.S. patents in the graphene thermal field. 

Noise Spectroscopy: In 1998, Dr. Balandin entered the field of low-frequency electronic noise as an electrical engineer, trying to reduce the 1/f noise in field-effect transistors based on wide-band-gap semiconductors (f is the frequency). The task was accomplished with the noise reduced by several orders of magnitude to the level acceptable for materials’ applications in communication systems. In 2009, Professor Balandin started investigating the noise in graphene and other 2D materials to remove the barrier for their applications in sensors, detectors, and communication devices. At about that time, he started to look at noise as a materials scientist and turned things upside down in the graphene electronic field by treating low-frequency noise as a signal. In Nano Letter (2012), his group demonstrated an innovative graphene sensor, where the noise was used as a signal – allowing one to distinguish different gases by characteristic peaks in the noise spectra. The group also discovered that the noise mechanism in graphene is not the same as in semiconductors, and used few-layer graphene to address the century-old problem of distinguishing if 1/f noise is a volume or a surface phenomenon. From 2016 the Balandin Group started to develop approaches for using noise measurements as a materials characterization tool to monitor phase transitions in charge density wave materials and other strongly correlated quantum materials. Current fluctuations, i.e. low-frequency noise, are more sensitive to phase transitions, and charge density wave depinning than the current-voltage characteristics. The innovative noise spectroscopy approaches were used to monitor charge density waves in 2D van der Waals materials. Noise spectroscopy was also applied to test the reliability of diamond and other ultra-wide-band-gap semiconductor devices. Professor Balandin was recognized for these achievements with the election to Fellow of SPIE, plenary talks at the top noise conference, e.g. International Conference on Noise and Fluctuations (ICNF), Gainesville, USA, and in Neuchâtel, Switzerland; serving as a General Chair of the SPIE Noise Conference and member of the international committee for Unsolved Problems of Noise (UPON); editing a book Noise and Fluctuations Control in Electronic Devices, which became a standard reference source; and invited review in Nature Nano on 1/f noise in graphene.

CDW Materials: In 2012, Professor Balandin became interested in strongly correlated phenomena in 2D materials. When researchers were trying to come up with a 2D material that has a bandgap and can complement the gap-less graphene, the Balandin Group focused on charge-density-wave (CDW) phenomena in 2D materials to achieve new device functionalities. In Nature Nano (2016), the group reported the first CDW quantum device, a voltage-controlled oscillator based on 2D CDW material, operational at room temperature. In 2023, the group achieved a breakthrough, reported in Advanced Materials (2023), demonstrating the first “quantum composite” with the unique functionality achieved via CDW condensate transitions above room temperature. Professor Balandin was recognized for these achievements with many invited talks on 2D and 1D CDWs materials at MRS Spring Meetings, APS March Meetings, SPIE conferences, and other top international conferences. In 2022, he was awarded The Vannevar Bush Faculty Fellowship to investigate 1D quantum materials.