Materials Literature
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We report on direct measurements of the impurity band hole polarization in the diluted magnetic semiconductor (Ga,Mn)As. The polarization of impurity band holes in a magnetic field is strongly enhanced by antiferromagnetic exchange interaction with Mn ions. The temperature dependence of the hole polarization shows a s…
Ist da noch ein Platz frei? Für die Bildung von Methanol aus CO und H2 an ZnO-Oberflächen wird auf der Grundlage von Rechnungen und Experimenten ein Mechanismus vorgeschlagen, bei dem CO an Sauerstoff-Fehlstellen des Heterogenkatalysators adsorbiert (siehe Bild; C rot, H weiß, O grau, Zn schwarz). Beigemischtes CO2 bl…
We demonstrate complete reversal of a full magnetic hysteresis loop of the magnetic semiconductor (Ga,Mn)As by ultrashort optical excitation with a single subpicosecond light pulse, with obvious implications for ultrafast magneto-optical recording. Our approach utilizes the fourfold magnetic anisotropy of (Ga,Mn)As, i…
Colloidal semiconductor quantum dots (QDs) have narrow photoemission bandwidths and broad absorption spectra that are ideal for multiplexing applications. In contrast to organic dyes, which require a complex arrangement of excitation sources and filters to generate multiple signals, many populations of QDs can be simu…
Tens to hundreds of micrometers long organic nanofibers have been generated from methoxy functionalized quaterphenylene molecules. The mutual alignment of the fibers is similar to that of previously reported nanofibers from para-hexaphenylene, and they emit intense, blue light centered at 400 nm with well resolved hig…
Both ${\mathrm{Cu}}_{5}{\mathrm{Zn}}_{8}$ and ${\mathrm{Cu}}_{9}{\mathrm{Al}}_{4}$ $\ensuremath{\gamma}$ brasses containing 52 atoms in its cubic cell have been recognized as a typical Hume-Rothery alloy phase, since these structurally complex compounds are stabilized at the same electron concentration of 1.61 electro…
We report the results from a study of europium-doped fluorochlorozirconate glasses that have been thermally processed to induce nucleation and crystallization of BaCl2 crystallites. The resulting glass ceramics show a photostimulated luminescence (PSL) effect with a conversion efficiency which is up to 80% of that fou…
High-resolution angle-resolved photoemission data from the insulating phase of the charge-density-wave (CDW) material $1T\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ reveal the backfolding of the electronic bands associated with the CDW superlattice, but also an additional, unexpected periodicity. This periodicity is cons…
We present a continuum description for the transition between the helicoid and spiral ribbon structures of chiral materials. At a critical value of the ratio between the bending and stretching moduli, the Föppl-von Kármán number, we encounter a continuous buckling transition from a straight helicoid to a spiral ribbon…
Recently we identified and classified a class of solids as kinking nonlinear elastic (KNE) because they deform by the formation of kink bands. KNE solids represent a large family that include, among others, layered ternary carbides and nitrides, layered oxides and semiconductors, zinc, cadmium, graphite, ice, and the…
We have studied the magnetic and magnetotransport properties of Mn-doped Ge grown by molecular-beam epitaxy. This group-IV dilute ferromagnetic semiconductor exhibits two magnetic transitions. An upper critical temperature TC* (∼112K for x∼0.05) is evident from the extrapolated Curie–Weiss susceptibility and from the…
The 4p states in transition metals and their compounds usually play minor roles on their physical quantities. Recent development of resonant x-ray scattering (RXS) at the K-edge of transition metals, however, casts light on the 4p states, because the signals on orbital and magnetic superlattice spots are brought about…
Using density functional theory, we study the magnetic stability of the Ga$_{1-x}$Mn$_x$N alloy system. We show that unlike Ga$_{1-x}$Mn$_x$As, which shows only ferromagnetic (FM) phase, Ga$_{1-x}$Mn$_x$N can be stable in either FM or antiferromagnetic phases depending on the alloy concentration. The magnetic order ca…
Total photoyield experiments are applied to characterize p-, intrinsic, and n-type diamond with hydrogen-terminated surfaces. On all hydrogen-terminated samples a photoelectron threshold energy of 4.4 eV is detected which is discussed in detail in this letter. We attribute this threshold to the energy gap between the…
A systematic ab initio study of the optical and electronic properties of BN nanotubes within density functional theory in the local density approximation is performed. Specifically, the optical dielectric function $\ensuremath{\epsilon}$ and the band structure of the single-walled zigzag [(5,0),(6,0),(9,0),(12,0),(15,…
The photoluminescence decay in amorphous semiconductors is described by power law $t^{-delta}$ at long times. The power-law decay of photoluminescence at long times is commonly observed but recent experiments have revealed that the exponent, $delta sim 1.2-1.3$, is smaller than the value 1.5 predicted from a geminate…
Electronic structure calculations for atomic wire of metals like Al, Ga and In are performed for a patterned dihydrogeneted Si(001):1 $\times$ 1 in search of structures with metallic behavior. The dihydrogeneted Si(001) is patterned by depassivating hygrozen atoms only from one row of Si atoms along the [1$\bar{1}$0]…
We present a unified band structure model to explain magnetic ordering in Mn-doped semiconductors. This model is based on the $p$-$d$ and $d$-$d$ level repulsions between the Mn ions and host elements and can successfully explain magnetic ordering observed in all Mn doped II-VI and III-V semiconductors such as CdTe, G…
We present exact electromagnetic solitary pulses that can be experimentally obtained within nonlinear left-handed metamaterials. The effect of pulse decoherence on the modulation instability of partially incoherent electromagnetic waves is also investigated. The results may contribute to a better understanding of nonl…
Formation of MnAs quantum dots in a regular ring-like distribution has been found on MBE-grown (GaMn)As surfaces after low-temperature annealing under As capping. The Mn was supplied by out-diffusing Mn interstitials from (GaMn)As. With 5 at% substitutional Mn the quantum dots appeared for (GaMn)As layers thicker than…