We report on the production of ordered assemblies silicon nanostructures by means irradiation a Si(100) substrate with 1.2 keV Ar ions at normal incidence. Atomic Force and High-Resolution Transmission Electron microscopies show that structures are crystalline, display homogeneous height, spontaneously arrange into short-range hexagonal ordering. Under prolonged (up to 16 hours) all dot characteristics remain largely unchanged small corrugation develops long wavelengths. interpret formation...

We have studied the influence of InP buffer-layer morphology in formation InAs nanostructures grown on InP(001) substrates by solid-source molecular-beam epitaxy. Our results demonstrate that when buffer layers are atomic-layer epitaxy, quantum dot-like structures formed, whereas MBE produce quantum-wire-like structures. The optical properties these corrugated make them potential candidates for their use light-emitting devices at 1.55 μm.

A lack of universality with respect to ion species has been recently established in nanostructuring semiconductor surfaces by low-energy ion-beam bombardment. This variability affects basic properties the pattern formation process, like critical incidence angle for formation, and remained unaccounted for. Here, we show that nonuniform generation stress across damaged amorphous layer induced irradiation is a key factor behind range experimental observations, as form field controlled...

Structural and optical characteristics of manganese doped cadmium sulfide nanoparticles prepared by <italic>in situ</italic> chemical synthesis using biocompatible Na-alginate biopolymer as a template is reported.

We report on the production of nanoscale patterning Si substrates by low-energy ion-beam sputtering. The surface morphology and structure irradiated were studied atomic force microscopy (AFM) high-resolution transmission electron (HRTEM). Under ion irradiation at off-normal incidence angle (~50°), AFM images show formation both nanoripple sawtooth-like structures for sputtering times longer than 20 min. latter feature coarsens appreciably after 60 min sputtering, inducing a large increase in...

We describe the conversion of yttrium, barium, and copper trifluoracetate-derived solid precursors to epitaxial YBa2Cu3Ox superconducting ceramics on (001)-oriented LaAlO3 substrates. Transmission electron microscopy, energy loss spectroscopy, energy-dispersive X-ray analysis, diffraction are used characterize reaction path nucleation mechanism yielding high critical current YBa2Cu3O7. Our results show that pyrolysis trifluoracetate solutions yields a nanostructured, partially amorphous...

The thermal-induced diffusion at nanoscale is investigated through the detailed study of structural and magnetic properties Co@Au nanoparticles as a function deposition temperature. Nanoparticles 10 nm were fabricated using an ion cluster source from Co95Au5 target. While low-temperature leads to formation alloyed fcc CoAu core with incomplete cobalt oxide shell, higher temperature induces pure hcp Co intermediate Au shell compact outer shell. evolution presented discussed in light changes...

A wet etching method for GaN and AlxGa1-xN, based on aqueous solutions of KOH, is presented. detailed analysis the rate dependence with temperature concentration described. This has been used fabrication high optical quality pyramidal nanostructures in wurtzite N-face grown AlN-buffered Si(111) substrates by molecular beam epitaxy. These have studied high-resolution transmission scanning electron microscopy their analysed low-temperature photoluminescence (PL) measurements. The pyramids are...

Pure Fe powders, milled down to 10 nm crystallite size, have been analyzed by a combination of M\"ossbauer spectroscopy, high resolution transmission electron microscopy, and magnetization measurements. After annealing the as-milled powders at 570 K for 1 hour, new phase is identified with hyperfine field 21 T, lower magnetic moment than bulk Fe, order-disorder transition temperature about 500 K, fcc crystal structure. It tentatively interpreted as magnetically ordered Fe.

We report on the magnetic and superconducting properties of La0.7Ca0.3MnO3/YBa2Cu3O7 (LCMO/YBCO) superlattices. For a constant LCMO layer thickness 6 unit cells (u.c.), resistance susceptibility measurements show superconductivity for YBCO in excess 4 cells. The critical temperature increases with thickness, Tc 58 K is found 10 Magnetization ferromagnetic transition at 100 (LCMO6 u.c./YBCO5 u.c.)15 bilayer superlattice, depressed value saturation magnetization 20 emu cm−3. These results are...

An MgO crystal was thermochemically reduced (TCR) under extreme reducing conditions such that the concentration of anion vacancies $(F$ centers) exceptionally large, $6\ifmmode\times\else\texttimes\fi{}{10}^{18}{\mathrm{cm}}^{\ensuremath{-}3}.$ Optical absorption measurements demonstrate in addition to F centers absorbing at $250\mathrm{nm},$ anion-vacancy clusters $355,$ $406,$ $440,$ $480,$ and $975$ nm were observed. Upon thermal annealing a atmosphere, broad extinction band 345 with full...

The study of the magnetic properties Co nanoparticles (with an average diameter 10.3 nm) grown using a gas-phase aggregation source and embedded in Au V matrices is presented. We investigate how matrix, number (counted by coverage percentage), interparticle interactions complex nanoparticles/matrix interface structure define studied systems. A threshold 3.5% monolayer was found both systems: below this coverage, behave as assembly independent single-domain entities with uniaxial anisotropy....

Ge nanoparticles embedded in an oxide matrix have been obtained by (a) steam thermal oxidation at 650 °C of polycrystalline SiGe layers and (b) deposition discontinuous films/SiO2 multilayers low pressure chemical vapour 390 annealing 700 °C. These two approaches are compared terms the composition size luminescence properties structures. In both cases violet peaking 3.1 eV is detected. The origin this emission types structures same it will be related to defects interface between...

The effect of an electron beam on the cathodoluminescence from indented MgO single crystals has been studied in scanning microscope. It found that luminescence intensity and spectrum vary with irradiation time. behavior is attributed to changes impurities vacancies defects.

The luminescence emission of structures containing Ge nanocrystals embedded in a dielectric matrix obtained by dry and wet oxidation polycrystalline SiGe layers has been studied as function the time initial layer thickness. A clear relationship between intensity luminescence, structure sample, formation process parameters that allows us to select appropriate conditions get most efficient established. evolution composition thickness growing oxides remaining during processes characterized...

In this article, multiwalled carbon nanotubes (MWNT) soluble in common organic solvents are prepared. The solubility is conferred to the MWNTs by covalent attaching of appropriately modified poly(vinyl chloride)(PVC). nucleophilic substitution PVC with potassium 4-hydroxythiophenolate carefully studied. It proceeds through a stereoselective mechanism. subsequent esterification reaction hydroxyl pendant groups (mPVC) carboxylic acids created MWNT reported. intermediates and final products...

The development of broadband and ultracompact optoelectronic devices relies on the possibility fabricating bright tunable emitters at nanoscale. Here, we show emission from EuOx (1 ≤ x < 1.4) thin films silicon formed by nanocrystals with average sizes in range 5 nm. photoluminescence nano-EuOx is as a function oxygen concentration changing green Eu2+-related to narrow red Eu3+-related emission. To reach these results has been instrumental through use new methodology specially designed...

Thermochemical reduction (TCR) at high temperatures has been performed on yttria-stabilized zirconia (YSZ), undoped and doped with Ni:Er, Co, or Pr. Investigations were carried out using optical absorption, luminescence, analytical electron microscopy. After TCR, crystals show an extinction band centered about 1.8 eV which is attributed to Mie scattering from precipitates average size of 10 nm, as observed by transmission In codoped TCR induced a broad 1.3 beginning 1600 K. Metallic Ni...