We demonstrate a surface enhanced Raman scattering (SERS) substrate by integrating plasmonic-active SiO₂ nanotubes into Si₃N₄ gratings. First, the dielectric grating that is working under guided mode resonance (GMR) provides enhanced electric field for localized surface plasmon polaritons on the surface of metallic nanoparticles. Second, we use SiO₂ nanotubes with...
Graphene is a promising material for applications in aqueous electrolyte environments. To explore the impact of such environments on graphene's electrical properties, we performed Hall bar measurements on electrolyte-gated graphene. Assuming a Drude model, we find that the room temperature carrier mobility in water-gated, SiO₂-supported graphene reaches 7000 cm²/Vs, comparable to...
We demonstrate that unidirectionally aligned, free-standing multi-walled carbon nanotubes (CNTs) exhibit highly anisotropic linear and nonlinear terahertz (THz) responses. For the polarization parallel to the CNT axis, strong THz pulses induce nonlinear absorption in the quasi-one-dimensional conducting media, while no nonlinear effect is observed in the perpendicular polarization configuration. Time-resolved...
We report an ultra-compact, cost-effective on-chip near-infrared spectroscopy system for CO₂ sensing using narrow-band optical filter array based on plasmonic gratings with a waveguide layer. By varying the periodicity of the gratings, the transmission spectra of the filters can be continuously tuned to cover the 2.0 μm sensing window with high...
Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar⁺ ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the...
The kinetics of laser-induced, liquid-mediated crystallization of amorphousGe thin films were studied using multi-frame dynamic transmission electron microscopy (DTEM), a nanosecond-scale photo-emission transmission electron microscopy technique. In these experiments, high temperature gradients are established in thin amorphousGe films with a 12-ns laser pulse with a Gaussian spatial profile. The hottest...
The need for miniaturization without compromising cost and performance continues to motivate research in advanced capacitor devices. In this report, multilayer ceramic capacitors based on relaxor BaTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) were fabricated and characterized. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1...
Using in-situ synchrotron X-ray scattering, we show that the structural evolution of various bulk metallic glass-forming liquids can be quantitatively connected to their viscosity behavior in the supercooled liquid near T[subscript g]. The structural signature of fragility is identified as the temperature dependence of local dilatation on distinct key atomic...
We show that the transmission of a terahertz (THz) pulse through single-layer graphene is strongly
nonlinear. As the peak electric field of the THz pulse exceeds 50 kV/cm, the graphene becomes
increasingly transparent to the THz radiation. When field strength reaches 800 kV/cm, the increased
transparency corresponds to a two-fold...
Metal-insulator-insulator-metal tunnel diodes with dissimilar work function electrodes and nanolaminate Al₂O₃-Ta₂O₅ bilayer tunnel barriers deposited by atomic layer deposition are investigated. This combination of high and low electron affinity insulators, each with different dominant conduction mechanisms (tunneling and Frenkel-Poole emission), results in improved low voltage asymmetry and non-linearity of current...
We demonstrate a versatile and efficient setup to perform femtosecond stimulated Raman spectroscopy (FSRS). Technical innovations are implemented to achieve the wavelength tunability for both the picosecond narrowband Raman pump pulse and femtosecond broadband Raman probe pulse. Using a simplified one-grating scheme in a home-built second harmonic bandwidth compressor followed...
We examined sub-nanosecond time-scale charge carrier dynamics in crystalline films of a functionalized anthradithiophene (ADT) donor (D) with three different acceptor (A) molecules. A four-fold enhancement in ultrafast charge carrier separation efficiency was observed in D/A blends with a fullerene acceptor added at 7–10 wt. % concentrations, whereas a gradual...
Passively generated lateral motion of fluid during pool boiling on asymmetrically textured mesoscale structures is discussed in this Letter. The surface texture is in the form of 30°–60° mm-scale ratchets with re-entrant cavities located on the 30° face. High speed visualization of growing bubbles from cavities indicates growth and departure...
All-optical switching has myriad applications in optoelectronics, optical communications, and
quantum information technology. To achieve ultrafast optical switching in a compact yet versatile
setup, we demonstrate distinct sets of two-dimensional (2D) broadband up-converted multicolor
arrays (BUMAs) in a thin type-I β-barium-borate crystal with two noncollinear near-IR
femtosecond pulses at various...
The role of back channel surface chemistry on amorphous zinc tin oxide (ZTO) bottom gate thin film transistors (TFTs) has been characterized by positive bias-stress measurements and x-ray photoelectron spectroscopy. Positive bias-stress turn-on voltage shifts for ZTO-TFTs were significantly reduced by passivation of back channel surfaces with self-assembled monolayers of...
Coherent phonon dynamics in condensed-phase medium are responsible for important material properties including thermal and electrical conductivities. We report a structural dynamics technique, time-resolved surface third-harmonic generation (TRSTHG) spectroscopy, to capture transient phonon propagation near the surface of polycrystalline CaF₂ and amorphous borosilicate (BK7) glass. Our approach time-resolves the background-free,...
We demonstrate remarkably strong nonlinear terahertz (THz) effects in an intrinsic GaAs wafer patterned with a nanometer-width slot antenna array. The antenna near-field reaches 20 MV/cm due to the huge field enhancement in the plasmonic nano-structure (field enhancement factor, α ≅ 50). The THz fields are strong enough to generate high density...
The electrode size dependence of the effective large signal piezoelectric response coefficient (d(33,f)) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed electrode size dependence is shown to arise from a contribution from the substrate. The...
In situ photoemission spectroscopy experiments are used to characterize the interface between ZnTe and the wide band gap p-type semiconductor BaCuSeF. The contact is characterized by a null valence-band offset, a large conduction-band offset, and a chemically graded interface. By applying the transitivity rule for band offset and on the...
Molybdenum disulfide (MoS₂) field effect transistors (FET) were fabricated on atomically smooth large-area single layers grown by chemical vapor deposition. The layer qualities and physical properties were characterized using high-resolution Raman and photoluminescence spectroscopy, scanning electron microscopy, and atomic force microscopy. Electronic performance of the FET devices was measured using...