β-Ga<sub>2</sub>O<sub>3</sub> is emerging as an interesting wide band gap semiconductor for solar blind photo detectors (SBPD) and high power field effect transistors (FET) because of its outstanding material properties including an extremely wide bandgap (Eg ~4.9eV) and a high breakdown field (8 MV/cm). This review summarizes recent trends and progress in the growth/doping of β-Ga<sub>2</sub>O<sub>3</sub> thin films and then offers an overview of the state-of-the-art in SBPD and FET devices. The present challenges for β-Ga<sub>2</sub>O<sub>3</sub> devices to penetrate the market in real-world applications are also considered, along with paths for future work.
Ultrafast optical spectroscopy can provide insight into fundamental microscopic interactions, dynamics and the coupling of several degrees of freedom. Pump/ probe studies can reveal the answer to questions like “What are the achievable switching speeds in multiferroics?”, “What is the influence of the crystallographic orientation and domain states on the available switching states?”, and “What is the effect of the hetrostructure on promoting the coupling between the varying field excitations?”. In this presentation, we report on two color (400/800nm) ultrafast pump-probe differential reflectance spectroscopy of BiFeO3-BaTiO3 structures to probe the coupling between optical and acoustic phonons to spin waves. The data presented here is a combination of different transient reflectivity measurements to probe both the carrier and spin dynamics. The (001)-BiFeO3-BaTiO3 thin films were prepared using pulsed laser deposition on vicinal SrTiO3 substrates using La0.70 Sr0.30MnO3 bottom electrodes. Crystal orientation and topography were analyzed by x-ray diffraction and atomic force microscopy. . Our results are important to developing devices on the basis of this material system.
This work was supported by the AFOSR through grant FA9550-14-1-0376,NSF-Career Award DMR-0846834, and the Virginia Tech Institute for Critical Technology and Applied Science.
We report on the use of two-photon absorption to photocleavage o-nitrobenzyl-based ligands bound to a gold surface with thiol
groups. Ablation of ligands occurs at high power densities, but this can be largely avoided by reducing the optical power level,
at which point two-photon mediated reactions still occur on a time scale of tens of seconds. This means that photoactive ligands
can be activated at wavelengths where plasmon resonances in gold and silver nanoparticles can easily be achieved, which will
allow the surface properties at the hot spots on plasmonic nanostructures to be chosen differently from the rest of the structure,
with possible applications in high-efficiency Surface-Enhanced Raman Spectroscopy and bottom-up nanoassembly.
The recent rapid progress in the field of spintronics requires extensive studies of carrier and spin relaxation dynamics in
semiconductors. In this work, we employed time and spin resolved differential transmission measurements in order to
probe carrier and spin relaxation times in several InAsP ternary alloys. In addition, the dynamics of the excitonic
radiative transitions of InAs<sub>0.13</sub>P<sub>0.87</sub> epitaxial layer were studied through the time-resolved photoluminescence