adsorbate induced self ordering of germanium nanoislands on si 113

The impact of Ga preadsorption on the spatial correlation of nanoscale three-dimensional (3D) Ge-islands has been investigated by low-energy electron microscopy and low-energy electron diffraction. Submonolayer Ga adsorption leads to the formation of a 2D chemical nanopattern, since the Ga-terminated (2×2) domains exclusively decorate the step edges of the Si(113) substrate. Subsequent Ge growth on such a partially Ga-covered surface results in Ge 3D islands with an increased density as compared to Ge growth on clean Si(113). However, no pronounced alignment of the Ge islands is observed. Completely different results are obtained for Ga saturation coverage, which results in the formation of (112) and (115) facets regularly arranged with a periodicity of about 40 nm. Upon Ge deposition, Ge islands are formed at a high density of about 1.3×1010 cm−2. These islands are well ordered as they align at the substrate facets. Moreover, the facet array induces a reversal of the Ge islands' shape anisotropy as compared to growth on planar Si(113) substrates

Superconductivity and physical properties of Ba24Si100 determined from electric transport, specific-heat capacity, and magnetic susceptibility measurements

Both Ba24Si100 and Ba24Ge100 with crystallographically identical structure are found to be superconducting at 1.4 and 0.27 K, respectively. Physical properties of this superconductor Ba24Si100 are studied by electric transport, specific heat capacity, and magnetic susceptibility measurements. The density of states at the Fermi level NEF=0.148 states eV-1(Siatom)-1 and a distinct jump of Cp at the superconducting transition temperature ΔCp=0.272JK-1mol-1 are obtained. An exponential fit of Cp below the superconducting states gives an energy gap 2Δ=0.423meV and shows that this is a superconductor having s-wave character or isotropic energy gap. On the basis of our experimental data other important physical parameters are also derived

STEREO PHOTOGRAPHY OF ATOMIC ARRANGEMENT AND ATOMIC-ORBITAL ANALYSIS BY TWO-DIMENSIONAL PHOTOELECTRON SPECTROSCOPY

The circular dichroism of photoelectron forward focusing peak rotation around the incident-light axis reflects the orbital angular momentum of the excited core level and is inversely proportional to the distance between the emitter and scatterer atoms. This is the basis for the stereo photograph of the atomic arrangements. These rotations are also found in the case of the valence band excitation. The rotation for the 2pxy band of graphite was about twice those from 2s and 2pz bands, corresponding to the difference in the orbital angular momentum quantum number of each band. Simultaneously, photoelectron intensity from the bottom of the 2s band was observed at the Γ point of every other Brillouin zone reflecting the photoelectron structure factor that corresponds to the interference of photoelectron waves from 2s atomic orbitals within a unit cell. The origin of the dual behavior that appeared in the observation of a local angular momentum from a delocalized valence band is discussed.Photoelectron, circular dichroism, orbital angular momentum

Stereophotographs of diamond and graphite

The direct imaging of atomic arrangement is essential for investigation of materials science. The rotation of forward focusing peaks in photoelectron intensity angular distribution (PIAD) pattern excited by circularly polarized light with the opposite helicities is found to be the same as the parallax in stereo view. Taking advantage of this phenomenon of PIAD circular dichroism, the three-dimensional atomic arrangement visualization of diamond and graphite crystal was realized. Taking a stereo picture around carbon atom, which has been thought difficult due to a small angular momentum and scattering cross section of photoelectron, proved that this method is applicable to various materials consisting of light elements. Furthermore, the local boron dopant site was concluded to be mainly substitutional one from the comparison of B 1s and C 1s PIAD patterns

Hydrogen Bond-Directed Self-Assembly of a Novel Pyrene Derivative

A symmetrical pyrene derivative chemical structure was prepared by a classical synthetic method such as the Sonogashira cross-coupling reaction. The molecular structure of the product was characterised in detail by nuclear magnetic resonance (NMR), mass spectrometry (MS) and other methods. Furthermore, the optical properties of the novel products were studied by UV-vis and photoluminescence spectroscopy. The electrochemical properties of the molecules were fully characterised by comparison of electrochemical experiments and DFT simulation. Scanning electron microscope (SEM) observed that the product successfully formed a regular self-assembly structure. The product verifies the role of the molecular structure of the disc-mounted molecules on the optical and self-assembly properties, and is of reference value in the field of organic optoelectronic molecule

Hydrogen Sulfide as an Endogenous Modulator in Mitochondria and Mitochondria Dysfunction

Hydrogen sulfide (H2S) has historically been considered to be a toxic gas, an environmental and occupational hazard. However, with the discovery of its presence and enzymatic production through precursors of L-cysteine and homocysteine in mammalian tissues, H2S has recently received much interest as a physiological signaling molecule. H2S is a gaseous messenger molecule that has been implicated in various physiological and pathological processes in mammals, including vascular relaxation, angiogenesis, and the function of ion channels, ischemia/reperfusion (I/R), and heart injury. H2S is an endogenous neuromodulator and present studies show that physiological concentrations of H2S enhance NMDA receptor-mediated responses and aid in the induction of hippocampal long-term potentiation. Moreover, in the field of neuronal protection, physiological concentrations of H2S in mitochondria have many favorable effects on cytoprotection