Rare-earth implanted Y2O3 thin films

Thin Er, Yb co-doped Y2O3 films were grown by pulsed laser deposition from ceramic target. Subsequent ion implantation with 1.1 MeV Er+ ions to a fluence of 6 × 1014 at/cm2 at room temperature was performed in order to modify the structure of the as-deposited films. The as-deposited films have a polycrystalline column-like structure. Ion implantation induces defects into the as-deposited films. After annealing at 900 °C for 1 h in oxygen atmosphere, the films recrystallize in roundly shaped grain-like structure with grain size of about 100 nm. The Er3+ photoluminescence response was obtained for all the films by excitation through cross-relaxation of Yb3+ ions. The IR emission spectrum, consisting of two narrow peaks at 1415 and 1514 nm, differs from the typical spectra of Er-doped materials. The VIS emission spectrum observed in as-deposited films does not appear after implantation and subsequent 900 °C annealing. © 2007 Elsevier B.V. All rights reserved.This work was supported in part by EU project NANOPHOS, Contract IST-2001-39112 and by the Bulgarian Ministry of Education and Science under Contract MUF-1511.Peer Reviewe

PLD fabrication of oriented nanowires in magnetic field

This paper presents an experimental investigation on laser-assisted fabrication of oriented nanowires composed by magnetic nanoparticles. The nanowires were produced by implementation of pulsed laser deposition in presence of a magnetic field. The application of an external magnetic field led to the formation of nanowires with a length of several micrometers whose orientation is influenced by the direction of the magnetic field lines. The influence of the type of ambient gas and its pressure on morphology and phase composition of the deposited samples was investigated. It was found that the ambient gas has direct influence on both the degree of orientation and the phase composition of the nanowires. SEM analysis of samples deposited at different targetsubstrate distances showed that the density of the nanowires decreases with the increase of the distance. A preliminary result on the magnetic properties of the produced nanowires is also reported

Au nanostructure fabrication by pulsed laser deposition in open air: Influence of the deposition geometry

We present a fast and flexible method for the fabrication of Au nanocolumns. Au nanostructures were produced by pulsed laser deposition in air at atmospheric pressure. No impurities or Au compounds were detected in the resulting samples. The nanoparticles and nanoaggregates produced in the ablated plasma at atmospheric pressure led to the formation of chain-like nanostructures on the substrate. The dependence of the surface morphology of the samples on the deposition geometry used in the experimental set up was studied. Nanocolumns of different size and density were produced by varying the angle between the plasma plume and the substrate. The electrical, optical, and hydrophobic properties of the samples were studied and discussed in relation to their morphology. All of the nanostructures were conductive, with conductivity increasing with the accumulation of ablated material on the substrate. The modification of the electrical properties of the nanostructures was demonstrated by irradiation by infrared light. The Au nanostructures fabricated by the proposed technology are difficult to prepare by other methods, which makes the simple implementation and realization in ambient conditions presented in this work more ideal for industrial applications

Growth mechanism of ZnO nanostructures produced by ultraviolet and visible laser ablation

ZnO nanostructures were fabricated on noble-metal (Au-Ag alloy) coated substrates by pulsed laser deposition. We studied the influence of the laser wavelength used for ablation on the morphology, growth mechanism, and optical properties of the nanostructures. ZnO nanostructures produced by UV (355 nm) pulsed laser deposition possessed a mixed-structures morphology, composed of nanorods (mean diameter of 25–50 nm) and large-size nanobelts. The density of these structures could be controlled by varying the Au/Ag ratio in the alloy layer. Samples deposited by pulsed laser deposition at VIS wavelength (532 nm), instead, presented a dense agglomeration of nanoparticles (nanorods) with a mean diameter in the range of 40–55 nm. The growth of the ZnO nanostructures followed a vapor-solid or vapor-liquidsolid mechanism depending on the catalyst layer composition when a UV source was used for ablation. The presence of Au and Ag on the ZnO surface was a clear indication for a vapor-liquid-solid mechanism of growth for nanostructures deposited by using a VIS radiation. A narrow peak centered at 379 nm in UV band and a broadband visible emission with a peak at 540 nm were observed in all nanostructures. The UV-deposited sample exhibited a stronger UV emission, while the visible emission was predominant for the sample deposited by VIS ablation

Noble metallic nanostructures: preparation, properties, applications

The process of formation and the characteristics are studied of noble metal nanostructures created by pulsed laser ablation in vacuum. Femtosecond (fs) and nanosecond (ns) laser systems lasing at different wavelengths are used. Several different modifications of the pulsed lased deposition (PLD) technique, as off-axis deposition and glancing angle deposition configurations are used to create nanostructures. Laser annealing of single or bimetal thin films is used to fabricate alloyed nanostructures. The possibility is demonstrated of tuning the optical properties of gold nanostructures on flexible substrates. Different experimental techniques, as fast photography, optical emission spectroscopy, FE-SEM, AFM, TEM, and Raman spectroscopy are applied to characterize the noble metallic nanostructures produced. The optical spectra of the Au and Ag nanostructures are also studied experimentally and theoretically. The theoretical simulation methods used are: molecular dynamic (MD), finite difference time domain (FDTD) and a method based on the generalized multi-particle Mie (GMM) theory. Applications of noble metal nanostructures to surface enhanced Raman spectroscopy (SERS) and biophotonics are briefly considered