A5038183739- Thermal properties of materials
- Thermal Radiation and Cooling Technologies
- Ion-surface interactions and analysis
- Acoustic Wave Phenomena Research
- Semiconductor Quantum Structures and Devices
- Spectroscopy and Quantum Chemical Studies
- Near-Field Optical Microscopy
- Laser-Plasma Interactions and Diagnostics
- Mechanical and Optical Resonators
- Microfluidic and Bio-sensing Technologies
- Laser Design and Applications
- Analytical Chemistry and Sensors
- Perovskite Materials and Applications
- Nonlinear Photonic Systems
- Carbon Nanotubes in Composites
- Fusion materials and technologies
- Organic Electronics and Photovoltaics
- Advancements in Semiconductor Devices and Circuit Design
- Laser-Matter Interactions and Applications
- Acoustic Wave Resonator Technologies
- Metal and Thin Film Mechanics
- Gas Dynamics and Kinetic Theory
- Organic and Molecular Conductors Research
- Advanced X-ray Imaging Techniques
- Metal Alloys Wear and Properties
Georgia Institute of Technology
2023
University of California, Santa Barbara
2019-2020
University of California System
2020
Santa Barbara City College
2020
Center for Research and Advanced Studies of the National Polytechnic Institute
2014-2018
Massachusetts Institute of Technology
2015-2017
University of Washington
2015
As is well-known, the phonon and electron thermal conductivity of a thin film generally decreases as its thickness scales down to nanoscales due size effects, which have dramatic engineering such overheating, low reliability, reduced lifetime processors other electronic components. However, given that thinner films higher surface-to-volume ratios, predominant surface effects in these nanomaterials enable transport energy not only inside their volumes but also along interfaces. In polar...
Studying thermal transport at the nanoscale poses formidable experimental challenges due both to physics of measurement process and issues accuracy reproducibility. The laser-induced transient grating (TTG) technique permits non-contact measurements on nanostructured samples without a need for metal heaters or any other extraneous structures, offering advantage inherently high absolute accuracy. We present review recent studies in silicon membranes using TTG technique. An overview...
We investigate the excitation of coherent acoustic and optical phonons by ultrashort extreme ultraviolet (EUV) pulses produced a free electron laser. Two crossed femtosecond EUV (wavelength 12.7 nm) are used to excite at wavelength 280 nm, which detected via diffraction an probe beam. Longitudinal surface waves measured in BK-7 glass, diamond, Bi4Ge3O12; latter material, phonon mode is also observed. discuss probing different modes reflection transmission geometries frequency mixing bulk...
Direct mesoscale measurements of radiation-induced changes in the mechanical properties bulk materials remain difficult to perform. Most widely used characterization techniques are either macro- or microscale nature, focusing on overall overly small areas for analysis. Linking atomic structure irradiated directly with their radiation-affected remains one largest unmet challenges radiation science. By measuring change surface acoustic wave speed as a function relative orientation metallic...
We report the experimental observation of an increase in elastic anisotropy tungsten upon He-ion implantation, probed optically using transient grating spectroscopy. Surface acoustic wave (SAW) velocity measurements were performed on a (110) oriented single crystal as function in-plane propagation direction for unimplanted and implanted samples. Our allow us to finely resolve remarkably small samples investigated. SAW calculations are used interpret data extract Zener parameter η constant...
Epitaxial growth of III-V semiconductors on Si is a promising route for silicon photonics. Threading dislocations and the residual thermal stress generated during are expected to affect conductivity semiconductors, which crucial efficient heat dissipation from photonic devices built this platform. In work, we combine non-contact laser-induced transient grating technique with ab initio phonon simulations investigate in-plane transport epitaxial GaAs-based buffer layers Si, employed in...
We present a modification of the laser-induced transient grating setup enabling continuous tuning period. The fine control period is accomplished by varying angle diffraction used to split excitation and probe beams. has been tested measuring dispersion bulk surface acoustic waves in both transmission reflection geometries. presented fully compatible with optical heterodyne detection can be easily implemented any setup.
We present a study on the many-body exciton interactions in Ruddlesden–Popper tin halide, namely, (PEA)2SnI4 (PEA = phenylethylammonium), using coherent two-dimensional electronic spectroscopy. The optical dephasing times of third-order polarization observed these systems are determined by and lattice fluctuations. investigate excitation-induced (EID) observe significant reduction time with increasing excitation density as compared to its lead counterpart (PEA)2PbI4, which we have previously...
We study the dynamics of an ordered hexagonal monolayer polystyrene microspheres adhered to a glass substrate coated with thin aluminum layer. A laser-induced transient grating technique is employed generate and detect three types acoustic modes across entire Brillouin zone in $\mathrm{\ensuremath{\Gamma}}\ensuremath{-}K$ direction: low-frequency contact-based granular monolayer, high-frequency originating from spheroidal vibrations microspheres, surface Rayleigh waves. The dispersion...
Attenuation of surface acoustic waves (SAWs) by a disordered monolayer polystyrene microspheres is investigated. Surface wave packets are generated pair crossed laser pulses in glass substrate coated with thin aluminum film and detected via the diffraction probe beam. When 170 μm-wide strip micron-sized spheres placed on between excitation detection spots, strong resonant attenuation SAWs near 240 MHz observed. The caused interaction contact resonance microspheres, as confirmed dispersion...
The thermal conductivity and viscosity of a magnetorheological suspension composed carbonyl iron particles immerse in silicone oil were studied. Thermal wave resonant cavity was employed to measure the diffusivity fluid as function an externally applied magnetic field. dynamic also measured its relationship with concentration field strength investigated. results show that higher concentrations well intensities lead significant increase conductivity. between explored. Our measurements...
Spiro-OMeTAD can be doped by infiltration of F<sub>4</sub>TCNQ from the vapor phase without causing crystallization. Optical spectroscopy and thermopower measurements examined question formation dication states charge transfer doping.
Heat transfer in silicone fluids loaded with high thermal conductivity carbon nanofibers was studied using photoacoustics and wave resonator cavity. It is shown that heat transport depends strongly on volume fraction of nanofibers; particular, a low loading percentage enough to obtain significant changes conductivity. Theoretical models were used determine how affected by structural formations the composite, such as packing aspect ratio (form factor) nanofiber agglomerates viscosity fluid...
Temperature dependence of the thermal diffusivity in composites epoxy and polyester resins, loaded with carbonyl iron particles, has been studied using photopyroelectric technique. Increments eight 2.5 times conductivity polymers are obtained, as volume concentration microparticles is increased from 0% to 40% for 20% matrices, respectively. Additionally, falls systematically temperature 270 400 K; effect more pronounced high composites. The glass transition explored by implementing a...
While charge carrier dynamics and thermal management are both keys to the operational efficiency stability for energy-related devices, experimental techniques that can simultaneously characterize properties still lacking. In this paper, we use laser-induced transient grating (TG) spectroscopy thin films of archetypal organic semiconductor regioregular poly(3-hexylthiophene) its blends with electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester on glass substrates. responses from film...
We present a study on the many-body exciton interactions in Ruddlesden-Popper tin halide, namely, (PEA)2SnI4 (PEA = phenylethylammonium), using coherent two-dimensional electronic spectroscopy. The optical dephasing times of third-order polarization observed these systems are determined by and lattice fluctuations. investigate excitation-induced (EID) observe significant reduction time with increasing excitation density as compared to its lead counterpart (PEA)2PbI4, which we have previously...
The study of heat transfer properties in mesoporous silicon, fabricated from highly doped p-type and n-type silicon wafers, is presented. Measurements were performed by a laser induced transient thermal grating technique, which allowed us to determine the effective (in-plane) conductivity. It shown that conductivity undergoes significant decrease with respect bulk values mainly due reduction phonon mean free path solid matrix. This can be ascribed formation nano-crystalline domains, are...