Materials Literature
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Skutterudites, such as CoSb3, are a promising class of thermoelectric materials, particularly when the voids in the crystal structure are filled with guest atoms. We report a comprehensive study of the effects of filling skutterudites with misch-metal (Mm), a rare-earth alloy having the naturally occurring La, Ce, Pr,…
Sc doping in Pb(Mg1∕3Nb2∕3)O3 enhances the B-site 1:1 cation order significantly but promotes the ferroelectric polar order moderately. At low doping levels, the electrical polar domains remain at the nanometer scale and the relaxor ferroelectric behavior is preserved. A normal ferroelectric state can be triggered wit…
A wide variety of enzymes can undergo a reversible loss of activity at low temperature, a process that is termed cold inactivation. This phenomenon is found in oligomeric enzymes such as tryptophanase (Trpase) and other pyridoxal phosphate dependent enzymes. On the other hand, cold-adapted, or psychrophilic enzymes, i…
We investigate the residual strains in a free-standing Cu/Nb multilayer of 30 nm nominal layer thickness with synchrotron x-rays. This material system is characterized by columnar grains of Cu and Nb with incoherent interfaces and a sharp physical-vapor-deposition texture. High energy x-rays were used with an area det…
We describe a device geometry using interdigital electrodes that enables the electrically driven reorientation of smectic A layers from a homeotropic state (dark between crossed polarizers) to a planar state (bright between crossed polarizers) and back again. The resulting electro-optic effect is strongly bistable and…
We have induced a metal-insulator transition in nondoped SrTiO3 by an electric field. The sheet carrier concentration of a SrTiO3 single-crystal surface was increased by electrostatic doping to 3.4×1012cm−2. A crossover from an insulating phase to a metallic state was clearly observed. The conduction mechanism in the…
We report on systematic measurements of the dephasing of the free excitonic transition in individual ZnO nanowires with a diameter of about 70nm. The temperature-dependent intensity of the free exciton (FX) emission is well reproduced by a thermally activated behavior having two constant activation energies of 5.98 an…
A heterojunction between thin films of nanocrystalline diamond (NCD) and 4H-SiC has been developed. Undoped and B-doped NCDs were deposited on both n− and p− SiC epilayers. I-V measurements on p+ NCD∕n− SiC indicated Schottky rectifying behavior with a turn-on voltage of around 0.2V. The current increased over eight o…
ZnO thin films prepared by pulsed laser deposition were implanted with phosphorous (P) using dose levels of 1012–1014ions∕cm2 at room temperature. The P-implanted films were subsequently annealed between 500 and 700°C in oxygen ambient. The Hall effect measurements revealed a substantial reduction in the electron conc…
Interference polarizing (Pluta and Interphako) microscopes have been used to measure the birefringence and refractive indices during the cold-drawing of isotactic poly(propylene) (iPP), poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) fibres. The intrinsic birefringence (Δn0) and refractive indice…
The relationship between retention loss in single crystal PbTiO3 ferroelectric thin films and leakage currents is demonstrated by piezoresponse and conductive atomic force microscopy measurements. It was found that the polarization reversal in the absence of an electric field followed a stretched exponential behavior…
We have observed nanoscale phase separation in amorphous arsenic trisulfide (As2S3) films produced by ultrafast pulsed laser deposition and its effect on the surface morphology of the film after plasma etching. When the film was etched in CF4–O2 plasma, a grainy structure was observed on the surface. From Raman and x-…
The fabrication of piezoelectric composites driven by the flexoelectric charge separation has aroused considerable interest recently. In earlier oral presentations, we have posited that, in such composites, even though the direct and the converse flexoelectric effects are thermodynamically equivalent, it is possible t…
Surface electromigration rates on oxide-free surfaces of unpassivated damascene Cu interconnect segments have been determined through electromigration testing under vacuum. Electromigration-induced voids grew at the cathode end of the segments due to a flux divergence at refractory-metal-lined vias to the lead lines b…
In this work, two systems of mesoporous bioglasses (MBGs) were sol-gel derived using block copolymer pluronic F127 and P123, respectively, as templates. A two-dimensional hexagonal (P6mm) mesoporous structure was obtained for the two systems, with d-spacing in (100) reflection of 8.49 nm for P123-templated MBG (P123-M…
Co-doped SnO2 nanocrystalline films have been fabricated by magnetron sputtering to investigate the effects of structural defects on mediating ferromagnetism in this system. X-ray photoelectron spectroscopy analysis reveals that Co element is incorporated into SnO2 lattice and is in 2+ oxidation state in all samples.…
After applying an electrical current pulse (ECP) to samples of Cu–Zn alloy, {111} oriented nanotwins parallel to the ECP direction in α phase grains have been observed at ambient temperature. It seems that (a) these samples have heated up to a temperature much higher than the α to β phase transformation temperature an…
Surface segregation effects play an important role in the growth of traditional III-V semiconductor heterointerfaces. Here we show that segregation processes can also set an upper limit to the obtainable interface sharpness in perovskite oxide heterostructures. In particular, the structure of LaVO3∕SrTiO3 superlattice…
We study structural disorder in ZnO bombarded at room temperature with 1.3 keV∕amu atomic P and cluster PFn (n=2 and 4) ions. Rutherford backscattering/channeling spectrometry results show that the density of collision cascades has a negligible effect on the damage buildup in the crystal bulk in the dose range resulti…
X-ray diffractions, Nomarski microscopy, scanning electron microscopy, and photoluminescence have been used to study the effects of substrate on the structure and orientation of ZnO thin films grown by rf-magnetron sputtering. GaAs(001), GaAs(111), Al2O3(0002) (c-plane), and Al2O3(11¯02) (r-plane) wafers have been sel…