A5034605945- Ultrasonics and Acoustic Wave Propagation
- Mechanical and Optical Resonators
- Acoustic Wave Resonator Technologies
- Thermal properties of materials
- Strong Light-Matter Interactions
- Plasmonic and Surface Plasmon Research
- Spectroscopy and Quantum Chemical Studies
- Thermal Radiation and Cooling Technologies
- GaN-based semiconductor devices and materials
- Nanowire Synthesis and Applications
- Thermography and Photoacoustic Techniques
- Geophysical Methods and Applications
- Terahertz technology and applications
- Solid-state spectroscopy and crystallography
- Photonic and Optical Devices
- Gold and Silver Nanoparticles Synthesis and Applications
- Acoustic Wave Phenomena Research
- Semiconductor Quantum Structures and Devices
- Magnetism in coordination complexes
- Molecular Junctions and Nanostructures
- Metal-Catalyzed Oxygenation Mechanisms
- Perovskite Materials and Applications
- Photoacoustic and Ultrasonic Imaging
- Silicon Nanostructures and Photoluminescence
- Metal and Thin Film Mechanics
Lund University
2016-2023
Hong Kong Polytechnic University
2018-2021
National Taiwan University
2012-2015
Centre National de la Recherche Scientifique
2008-2014
Institut d'électronique de microélectronique et de nanotechnologie
2008-2014
Université de Lille
2010
École Centrale de Lille
2010
Institut Supérieur de l'Électronique et du Numérique
2008-2009
Abstract Despite the great amount of attention CH 3 NH PbI has received for its solar cell application, intrinsic properties this material are still largely unknown. Mobility charges is a quintessential property in aspect; however, there no clear understanding electron transport, as reported values span over three orders magnitude. Here we develop method to measure and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply characterize...
Molecular aggregates on plasmonic nanoparticles have emerged as attractive systems for the studies of polaritonic light-matter states, called plexcitons. Such are tunable, scalable, easy to synthesize, and offer sub-wavelength confinement, all while giving access ultrastrong coupling regime, promising a plethora applications. However, complexity these materials prevented understanding their excitation relaxation phenomena. Here, we follow pathways in plexcitons conclude that metal destroys...
Despite the numerous devoted studies, water at solid interfaces remains puzzling. An ongoing debate concerns nature of interfacial a hydrophilic surface, whether it is more solid-like, ice-like, or liquid-like. To answer this question, complete picture distribution molecule structure and molecular interactions has to be obtained in non-invasive way on an ultrafast time scale. We developed new experimental technique that extends classical acoustic level. Using nanoacoustic waves with...
Complete mechanical measurements are performed in submicron films using the picosecond ultrasonic technique. The Al layer deposited on top of sample acting as a transducer is replaced with nanostructured film. Using an usual setup we can excite and detect high-frequency longitudinal surface acoustic waves. From this deduce Young’s modulus Poisson’s ratio any isotropic thin Experimental results obtained for silica silicon very good agreement literature.
Practically, graphene is often deposited on substrates. Given the major substrate-induced modification of properties and considerable energy transfer at interface, graphene-substrate interaction has been widely discussed. However, proposed mechanisms were restricted to two-dimensional (2D) plane while conduction in third dimension hardly considered. Herein, we disclose perpendicular interface combined system 2D 3D base. More precisely, our observation dissipation optically excited via...
We study the elastic properties of two-dimensional phononic crystals made aluminum nanocube lattices. From experimental point view, collective modes resulting from coupling between cubes inside crystal are excited and time resolved using ultrafast acoustics. derive a general theoretical model modes. analytical expression we discuss influence numerous parameters on detected frequencies. then present results various samples which all exhibit an excellent agreement with model. The description...
Abstract The fascinating relationship between structure and property in nanowires has enabled a wealth of applications photonics electronics. behavior phonons is also modified compared to their bulk counterparts. In this review, we provide an overview the recent efforts investigate properties acoustic using ultrafast optical methods. particular, focus on calculation phonon dispersion how address them optically. We then discuss experimental investigations arrays single nanowire. analysis...
We have developed and demonstrated an experimental method, based on the picosecond acoustics technique, to perform nondestructive complete mechanical characterization of nanowires, that is, determination elasticity tensor. By means femtosecond pump-probe spectroscopy, coherent acoustic phonons were generated in ensemble nanowires their dynamics was resolved. Specific phonon modes identified detection mechanism addressed via wavelength dependent experiments. calculated exact dispersion...
In polaritons, the properties of matter are modified by mixing molecular transitions with light modes inside a cavity. Resultant hybrid light-matter states exhibit energy level shifts, delocalized over many units, and have different excited-state potential landscape, which leads to exciton dynamics. Previously, non-Hermitian Hamiltonians been derived describe excited molecules coupled surface plasmons (i.e., plexcitons), these operators successfully used in description linear third order...
Understanding of recombination and photoconductivity dynamics photogenerated charge carriers in GaxIn1-xP NWs is essential for their optoelectronic applications. In this letter, we have studied a series with varied Ga composition. Time-resolved photoinduced luminescence, femtosecond transient absorption, time-resolved THz transmission measurements were performed to assess radiative nonradiative charges the NWs. We conclude that limited by hole trapping, whereas electrons are highly mobile...
We present experimental results demonstrating that the generation of terahertz acoustic waves using femtosecond laser pulses is possible in quantum dots (QDs). Very short and strong are emitted from a buried QD layer detected at sample surface. By tuning wavelength we can detect, room temperature, frequencies above 1 THz photoelastic mechanism. A theoretical model supports such capability shows around an interband transition bandwidth detection be greatly improved. These suggest...
The generation of guided acoustic phonons in the GHz range GaN/AlN superlattices grown atop a GaN nanowire is presented. Combined with femtosecond laser, ultrafast pump–probe spectroscopy allows and detection at different frequencies superlattices. capability to be excellent detectors specific then used observe strong dispersion, as result nanoconfinement, after their propagation nanowire. high frequency coherent could useful not only realize an transducer nanolateral size but also source...
The coupling of plasmonic resonances with the multiple phonon modes a supracrystal is studied. Ultrafast optical pump-probe spectroscopy variable wavelength allows selective detection breathing mode, interparticle vibrations, and vibration whole structure. Thanks to this selectivity, characterization bonding strength between nanoparticles in different directions possible. observation these vibrations could be useful for realization future modulated photonic devices.
A phonon nanoscopy method, based on the picosecond ultrasonics technique, capable of studying complex acoustic reflection coefficient at frequency up to 1 THz is proposed and demonstrated. By measuring same surface location interface between GaN air, material characterize, we get access amplitude phase spectra reflection. The retrieval both these pieces information then allows calculation attenuation in a wide range gives new insight into Kapitza anomaly. This method applied cubic ice,...
Despite the enormous amount of attention CH3NH3PbI3 has received, we are still lacking an in-depth understanding its basic properties. In particular, directional mechanical and structural characteristics this material have remained elusive. Here, investigate these properties by monitoring propagation longitudinal shear phonons following absorption a femtosecond pulse along various crystalline directions single crystal. We first extract sound velocities transverse Our study then reveals...
Oligonuclear complexes of d4–d7 transition metal ion centers that undergo spin-switching have long been developed for their practical role in molecular electronics. Recently, they also appeared as promising photochemical reactants demonstrating improved stability. However, the lack knowledge about photophysical properties solution phase compared to mononuclear is currently hampering inclusion into advanced light-driven reactions. In present study, ultrafast photoinduced dynamics a solvated...
An atomistic understanding of the photoinduced spin-state switching (PSS) within polynuclear systems d4–d7 transition metal ion complexes is required for their rational integration into light-driven reactions chemical and biological interest. However, in contrast to mononuclear systems, multidimensional dynamics PSS solvated molecular arrays have not yet been elucidated due expected complications associated with connectivity between centers strong interactions surroundings. In this work, a...
Radial breathing oscillation of 2-D arrayed GaN nanorods was successfully excited in rods with different diameters by using femtosecond transient reflectivity measurement. Through analyzing thus measured diameter dependent frequency, we discovered that modification the mechanical property appeared piezoelectric nanorods, fabricated on top a bulk substrate, when rod order or less than 50 nm. Our measurement observed much reduced elastic stiffness constant (C11) 193 ± 24 GPa 35nm compared 365...
Scattering of photons by phonons, or Brillouin scattering, enables manipulation and control light has led to revolutionary applications, from slow saser cooling micromechanical resonators. Recently, enhanced sound interaction been demonstrated in waveguides. However, the design waveguide geometry tunes alters phonon photon dispersion simultaneously. Here we investigate, through femtosecond pump-probe spectroscopy theoretical modeling, a bottom-up fabricated vertical nanowire photonic...
Femtosecond pump probe spectroscopy experiments were carried out to observe extensional modes of GaN nanorods. Different orders generated and observed following the absorption femtosecond light pulses. This observation confirms that with a diameter on order 100 nm, no mechanical change is expected compared bulk GaN. We propose demonstrate detection these achieved through modulation Fabry-Pérot cavity formed by nanorod array. The nanorods length thus modify reflectivity rod-array cavity.
We demonstrate that guided acoustic waves inside a nanorod can be excited through an external metallic transducer. By attaching gold nanodisks on top of GaAs nanorods, the femtosecond optical excitation transducer enables generation in rods. The propagation behavior and mode shape observed are analyzed. These observations would not only lead to development superior transducers for imaging, but also provide experimental system study phonon transport nanorods nanowires.
We report a method that enables the excitation of localized surface plasmons (LSPs) in gold nanodisk array by placing each on top GaN nanorod. When rod length was much longer than plasmon penetration depth inside nanorod, plasmonic field found to be localized, and coupling between neighboring nanodisks eliminated. The interaction LSPs acoustic vibrations then investigated. Owing strong localization field, weak, higher-order vibrational modes could optically observed. Furthermore, such an...
First Page
Picosecond acoustics is the perfect technique for measuring elastic properties at nanoscale. But there still are some limitations to reach in-plane of ultra-thin films related optical detection ultra-high frequency surface acoustic waves. Here, we demonstrate that it possible push limits using an interferometric instead a usual reflectometry scheme. The experimental observations supported by simple model which explains from where comes previous and why overcome setup. Thanks those results,...