Materials Literature
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We implement metallic layers of Si-doped (110) GaAs as modulation doping in high mobility p-type heterostructures, changing to p-growth conditions for the doping layer alone. The strongly auto-compensated doping is first characterized in bulk samples, identifying the metal-insulator transition density and confirming c…
We first report a detailed transmission electron microscopy study of dislocation networks (DNs) formed at shallowly buried interfaces obtained by bonding two GaAs crystals between which we establish in a controlled manner a twist and a tilt around a k110l direction. For large enough twists, the DN consists of a twodim…
The mechanisms limiting the spin coherence time of electrons are of great importance for spintronics. We present electron spin resonance (ESR) and transport measurements of six different two dimensional electron gases in silicon/silicon-germanium (Si/SiGe 2DEGs). The spin decoherence time $T_2^*$ is presented in conju…
We account for lateral orderings of III-V nanostructures resulting from a GaAs/InAs/InGaAs/GaAs sequence grown on GaAs by metallorganic vapour phase epitaxy at two different temperatures. For both samples, the ordering is induced by the stress field of a periodic dislocation network (DN) shallowly buried and parallel…
Microhardness measurements have been carried out on high purity Cu samples with average grain sizes ranging from ∼10 to ∼200nm, over temperatures from liquid nitrogen to ambient, and dwell-times of the indenter in the sample from 5 s to 39 h. The Vickers hardness diminishes approximately linearly with the logarithm of…
Strongly p-type ZnO is produced by the following sequence of steps: (1) evaporation of Zn3As2 on a fused-quartz substrate at 350°C; and (2) sputtering of ZnO with substrate held at 450°C. The electrical characteristics include: resistivity of 0.4Ωcm, a mobility of 4cm2∕Vs, and a hole concentration of about 4×1018cm−3.…
In this article we review recent work on the development and study of the properties of self-organising supermolecular and supramolecular materials, that are in size comparable to small proteins. We take the concept of the creation of dendritic liquid crystals, and apply it to the creation of new materials with single…
Silicon nanocrystals were in situ grown in a silicon nitride film by plasma-enhanced chemical vapor deposition. The size and structure of silicon nanocrystals were confirmed by high-resolution transmission electron microscopy. Depending on the size, the photoluminescence of silicon nanocrystals can be tuned from the n…
Surfactant-free oil-in-water emulsions prepared with temperature and pH sensitive poly(N-isopropylacrylamide)(PNIPAM) microgel particles offer unprecedented control of emulsion stability.
Methods for quantifying environmentally induced decoherence in quantum systems are investigated. We formulate criteria for measuring the degree of decoherence and consider several representative examples, including a spin interacting with the modes of a bosonic, e.g., phonon, bath. We formulate an approach based on th…
In systems considered for quantum computing, i.e., for control of quantum dynamics with the goal of processing information coherently, decoherence and deviation from pure quantum states, are the main obstacles to fault-tolerant error correction. At low temperatures, usually assumed in quantum computing designs, some o…
We introduce a new approximation scheme for evaluation of onset of decoherence at low temperatures in quantum systems interacting with environment. The approximation is argued to apply at short and intermediate times. It provides an approach complementary to Markovian approximations and appropriate for evaluation of q…
We have used coherent, resonant, x-ray magnetic speckle patterns to measure the statistical evolution of the microscopic magnetic domains in perpendicular magnetic films as a function of the applied magnetic field. Our work constitutes the first direct, ensemble-averaged study of microscopic magnetic return point memo…
Using coherent x-ray speckle metrology, we have measured the influence of disorder on major loop return point memory (RPM) and complementary point memory (CPM) for a series of perpendicular anisotropy Co/Pt multilayer films. In the low disorder limit, the domain structures show no memory with field cycling--no RPM and…
Diluted magnetic semiconductors currently attract immense experimental and theoretical attention as one of the most promising classes of materials for spintronic applications. We report a detailed density-functional-theory study of the influence of the clustering of the substitutional Mn impurities on the electronic s…
The crystal structures of M 1+ x V 3 O 8 , where M 1+ x = Ag 1.229 and Na 1.164 , isomorphous to the Li 1+ x V 3 O 8 insertion electrode have been determined with x-ray four-circle diffraction. The networks of V ions are similar to each other, but significant differences for the M–O and M–M distances exist. The presen…
This paper presents an approach for the thermal control of an artificial anal sphincter using shape memory alloys. An artificial anal sphincter has been proposed by the authors to resolve problems of severe fecal incontinence in patients. The basic design of the artificial sphincter consists of two all-round shape mem…
Ceramics in the (BiMnO 3 ) x –(PbTiO 3 ) 1− x series were fabricated with compositions in the range . A macroscopically pseudocubic structure was observed for compositions x >0.4 while at x <0.4 the structure is tetragonal. The presence of a pseudocubic structure is attributed to frustration between different preferre…
We have used density functional pseudopotential calculations and molecular dynamics to predict new carbon structures of high stability. The new phases are strongly bound and involve the smallest radius nanotubes. It was found that it is possible to covalently link smallest/larger, smallest/smallest radius nanotubes to…
It is of high fundamental and practical importance to be able to control the formation and stability of the different crystalline phases of alumina (Al 2 O 3 ). In this study, we have used density functional theory methods to investigate the changes induced in the thermodynamically stable α phase and the metastable θ…