Growth of ZnO nanostructures on Si by means of plasma immersion ion implantation and deposition

Crystalline zinc oxide (ZnO) nanostructures have been grown on Si substrates by means of Plasma Based Ion Implantation and Deposition (PIII&D) at temperature of about 300 0C and in the presence of an argon glow discharge. In the process a crucible filled with small pieces of metallic zinc plays the role of the anode of the discharge itself, being polarized by positive DC voltage of about 400V. Electrons produced by thermionic emission by an oxide cathode (Ba, Sr, Ca)O impact this crucible, causing its heating and vaporization of Zn. Partial ionization of Zn atoms takes place due to collisions with plasma particles. High negative voltage pulses (7 kv/40μs/250Hz) applied to the sample holder cause the implantation of metallic zinc into Si surface, while Zn deposition happens between pulses. After annealing at 700 0C, strong UV and various visible photoluminescence bands are observed at room temperature, as well as the presence of ZnO nanoparticles. The coated surface was characterized in detail using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. XRD indicated the presence of only ZnO peaks after annealing. The composition analysis by EDS revealed distinct Zn/O stoichiometry relation depending on the conditions of the process. AFM images showed the formation of columns in the nanoscale range. Topography viewed by SEM showed the formation of structures similar to cactus with nanothorns. Depth analysis performed by XPS indicated an increase of concentration of metallic Zn with increasing depth and the exclusive presence of ZnO for outer regions. PIII&D allowed to growing nanostructures of ZnO on Si without the need of a buffer layer

Stock-Returns and Inflation in a Principal-Agent Economy

We study a monetary in which final goods sell on spot markets, while labor and dividends sell through contracts. Firms and workers confuse absolute and relative price changes: A positive price-level shock makes sellers think they are producing better goods than they really are. They split this apparent windfall with workers who get a higher real wage. Hence, unexpected inflation shifts real income from firms (the principals) to workers (the agents) and thereby lowers stock-returns.MONEY SUPPLY ; PRICES ; STOCKS

Evaluation of Effective Astrophysical S factor for Non-Resonant Reactions

We derived analytic formulas of the effective S astrophysical S factor,S^eff for a non-resonant reaction of charged particles using a Taylor expension of the astrophysical S factor and a uniform approximation.The formulas will be able to generate generate more accurate approximation to S^eff than previous ones

Determination of Boundary Scattering, Intermagnon Scattering, and the Haldane Gap in Heisenberg Chains

Low-lying magnon dispersion in a S=1 Heisenberg antiferromagnetic (AF) chain is analyzed using the non-Abelian DMRG method. The scattering length $a_{\rm b}$ of the boundary coupling and the inter-magnon scattering length $a$ are determined. The scattering length $a_{\rm b}$ is found to exhibit a characteristic diverging behavior at the crossover point. In contrast, the Haldane gap $\Delta$, the magnon velocity $v$, and $a$ remain constant at the crossover. Our method allowed estimation of the gap of the S=2 AF chain to be $\Delta = 0.0891623(9)$ using a chain length longer than the correlation length $\xi$.Comment: 6 pages, 3 figures, 1 table, accepted in Phys. Rev.