Materials Literature
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We have investigated the relaxation of zone-center nonequilibrium optical phonons in bulk cubic and hexagonal semiconductors. Our theory is based on the application of Fermi's golden rule formula involving anharmonic interaction between phonons. Calculations of the lifetimes of the zone-center longitudinal optical (LO…
Metamaterials composed of metal-dielectric nanostructures can be engineered to have the real part of the effective refractive index less than unity at optical wavelengths. These materials show intriguing optical properties including total external reflection. We utilize this effect to design and analyze slab waveguide…
We present a Raman spectroscopy study of iodine-intercalated ($p$-type-doped) double-walled carbon nanotubes. Double-walled carbon nanotubes ($\mathrm{DWCNTs}$) are synthesized by catalytic chemical vapor deposition and characterized by Raman spectroscopy. The assignment of the radial breathing modes and the tangentia…
Molecular dynamic calculations of pullout in multiwall carbon nanotubes (CNTs) demonstrate that inner walls with fractured ends have pullout forces $\ensuremath{\sim}3\ensuremath{-}4$ times larger than those for capped ends, due to deformation of the fractured end, quantitatively accounting for experiments. Under pres…
Functionalized beads and particles in the size range of tens to hundreds of nanometers (nano- to meso-scale) are finding increased applications in the bioanalytical field. We show here that conjugates of streptavidin and the temperature-responsive polymer poly(N-isopropylacrylamide) (PNIPAAm), synthesized with low pol…
Work functions of individual single-walled carbon nanotubes (SWNTs) were studied by means of photoemission electron microscopy. Work function differences between the nanotubes were clearly observed in secondary electron images. The work functions of 93 SWNTs were found to range within 0.6eV, but most distributed in a…
Nitrous oxide (N2O) reduction is a chemical challenge both in the selective oxidation of organic substrates by N2O and in the removal of N2O as a green-house gas. The reduction of N2O is thermodynamically favorable but kinetically inert, and requires activating transition-metal centers. In biological systems, N2O redu…
Macromolecular anchoring layer approach was used for preparation of an effective macroinitiator for the synthesis of grafted polymer layers by atom transfer radical polymerization (ATRP) initiated from the surface. For the initial surface modification, a thin layer of poly(glycidyl methacrylate) (PGMA) was deposited o…
Sensitization of Er emission by Si nanoclusters (Si-nc) is investigated with pulsed and continuous optical pumping, in and off resonance with excited states of ${\text{Er}}^{3+}$ ion. We show that under high-power pulsed pumping, the excitation process is limited by the finite energy transfer time from Si-nc to ${\tex…
This work describes studying the permanent grafting of carboxylic acid end-functionalized poly(ethylene glycol) methyl ether (PEG) chains of different molecular weights from the melt onto a surface employing poly(glycidyl methacrylate) ultrathin film as an anchoring layer. The grafting led to the synthesis of the comp…
Germanium-based alloys hold great promise for future spintronics applications, due to their potential for integration with conventional Si-based electronics. Mn5Ge3 exhibits strong ferromagnetism up to the Curie temperature Tc~295K. We use Point Contact Andreev Reflection (PCAR) spectroscopy to measure the spin polari…
The structure and electronic properties of single $\mathrm{Cu}$ atoms, copper monolayers, and thin copper films on the polar oxygen and zinc terminated surfaces of $\mathrm{ZnO}$ are studied using periodic density-functional calculations. We find that the binding energy of $\mathrm{Cu}$ atoms sensitively depends on ho…
The films of order-disorder type ferroelectrics were considered in the mean field approximation taking into account depolarization field. It was shown that size effects in this system could be described on the base of bulk system equation of state with Curie temperature dependent on the film thickness. The critical si…
We have developed a method to simulate multiple electron scattering in a vacuum barrier using real-space single-electron wavefunctions of the separate surfaces. The tunnelling current is calculated to first order in the Dyson series. In zero order, we find a result which differs from the usual Bardeen approach by the…
We performed ab initio calculations of the optical absorption spectrum and the wave-vector-dependent dielectric and energy-loss functions of graphite in the framework of the random-phase approximation. In the absorption spectrum, the most prominent peaks were analyzed in terms of interband transitions from specific re…
We demonstrate a single-walled carbon nanotube p-n junction diode device. The p-n junction is formed along a single nanotube by electrostatic doping using a pair of split gate electrodes. By biasing the two gates accordingly, the device can function either as a diode or as an ambipolar field-effect transistor. The dio…
We report the first experimental demonstration of a novel single-layer subwavelength grating (SWG) that has >500-nm-wide reflection spectrum from 1.12-1.62 μm and very high reflectivity (>98.5%). This SWG is scalable for different wavelengths by simply changing the grating dimensions, which, thus, facilitates monolith…
First-principles calculations have been performed on lithium borohydride $\mathrm{Li}\mathrm{B}{\mathrm{H}}_{4}$ using the ultrasoft pseudopotential method, which is a potential candidate for hydrogen storage materials due to its extremely large gravimetric capacity of $18\phantom{\rule{0.3em}{0ex}}\text{mass}\phantom…
As a consequence of the growing theoretical predictions of 100% spin-polarized half- and full-Heusler compounds over the past six years, Heusler alloys are among the most promising materials class for future magnetoelectronic and spintronic applications. We have integrated Co2MnSi, as a representative of the full-Heus…
Lead-free piezoelectric ceramics (0.95−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3–0.05BaTiO3 (abbreviated as BNT–BKT–BT100x, with x ranged from 0 to 20mol%) have been studied. Effects of amount of BKT on the electrical properties and crystal structure were examined. BNT–BKT–BT5 ceramics give good performances with piezoelect…