Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

High-density electron anions in a nanoporous single crystal: [Ca24Al28O64]4+(4e-).

Abstract: We removed approximately 100% of clathrated oxygen ions from the crystallographic cages in a single crystal of 12CaO.7Al2O3, leading to the formation of high-density (approximately 2 x 10(21) cm-3) electrons highly localized in the cages. The resulting electron forms a structure that we interpret as an F+ center and migrates throughout the crystal by hopping to a neighboring cage with conductivity approximately 100 siemens per centimeter, demonstrating that the encaged electron behaves as an anion. The electron anions couple antiferromagnetically with each other, forming a diamagnetic pair or singlet bipolaron. The resulting [Ca24Al28O64]4+(4e-) may be regarded as a thermally and chemically stable single crystalline "electride."

Experimental Evidence of the Viscous Behavior of Grain Boundaries in Metals

Abstract: The mechanical behavior of grain boundaries in metals has been a subject of constant controversy. The present research is designed to examine thoroughly the mechanical behavior of grain boundaries in metals in a quantitative manner. A simple torsional apparatus has been devised for measuring four types of anelastic effects at very low stress levels, namely: internal friction at low frequencies; variation of dynamic rigidity with temperature; creep under constant stress; and stress relaxation at constant strain. All four types of anelastic effects have been studied in 99.991 percent polycrystalline aluminum as well as in single crystal aluminum; these effects are practically absent in single crystal aluminum. The four types of anelastic effects observed in polycrystalline aluminum are completely recoverable and are linear with respect to the applied stress and prior strain. They satisfy the interrelations derived by Zener from Boltzmann's superposition principle within experimental error. These are consistent with the viewpoint that the grain boundaries behave in a viscous manner. The maximum amount of shear stress relaxation in polycrystalline aluminum determined by the four types of anelastic measurements is about 33 percent. This is in good agreement with the theoretical value of 36 percent calculated by assuming the grain boundary to be viscous. The heat of activation associated with the viscous slip along the grain boundaries has been found to be 34,500 calories per mole. The coefficient of viscosity of the grain boundaries in aluminum estimated using this heat of activation, is consistent with that of molten aluminum at the same temperature. Similar anelastic effects have been also observed in polycrystalline magnesium, indicating that the viscous behavior is common to all metals.

Epitaxial graphene on Cu(111).

Abstract: The growth of graphene on single crystal Cu(111) has been achieved by thermal decomposition of ethylene in an ultrahigh vacuum chamber for the first time. The structural and electronic properties of graphene on Cu(111) have been investigated by scanning tunneling microscopy and spectroscopy. The nucleation of monolayer islands and two predominant domain orientations have been observed, which lead to the formation of numerous domain boundaries with increasing coverage. These results reveal that reducing the density of domain boundaries is one challenge of growing high-quality graphene on copper.

Single Crystal Formamidinium Lead Iodide (FAPbI3): Insight into the Structural, Optical, and Electrical Properties.

Abstract: 5 mm-scale large FAPbI 3 single crystals and corresponding photoconductive properties are shown. The phase transition of FAPbI3 between the α-phase and δ-phase is studied. The carrier mobility is 4.4 cm(2) V(-1) s(-1) with a lifetime of 484 ns in the bulk of the single crystal. Finally, photodetectors based on single-crystal FAPbI3 are demonstrated.