The use of self-assembled block copolymer structures to direct the formation of large area nanoscale features could
provide a silicon-based fabrication-compatible means to supplement conventional lithographic techniques. Here, self-assembled
monolayers of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer were utilized as
structural elements for the production of pseudo-hexagonal close packed metallic nanoarrays. Metal ion loading of the
P2VP block with simple aqueous solutions of anionic metal complexes is accomplished via protonation of this basic
block, rendering it cationic; electrostatic attraction leads to a high local concentration of metal complexes within the
protonated P2VP domain. The ordering of the copolymer micelles can be enhanced by solvent vapor annealing. The
resulting templated large area metallic nanoclusters can serve as periodic seeds to grow nanofibrous thin films, which
inherit the periodicity of the underlying seeds, by glancing angle deposition (GLAD). GLAD offers a high level of
control over the composition and porosity of thin films microstructures, and has been used to make uniform and highly
porous thin film architectures for applications such as photonic crystals.
Luminescent thin films are used for many applications, including light-emitting diodes, lasers and flat panel
displays. Glancing angle deposition (GLAD) is a physical vapor deposition technique which relies on highly
oblique flux angles to create porous thin films. When combined with real-time substrate motion control and
measurement of deposition rates, it is possible to produce high quality nanostructered thin films. A rugate filter
uses a sinusoidally varying index profile to produce a stop band. Using the GLAD technique, it is possible to
produce a rugate filter from a single material. The central wavelength, depth and width of the stop band can be
designed by adjusting the film nanostructure. In this paper, rugates composed of Y2O3:Eu are used to control
the angular emission profiles of the photoluminescent thin film. Confined, annular and isotropic emission profiles
film is nearly uniform for emission angles
between ~ -60° and ~60°.
A Quantum-dot saturable absorber mirror (QD-SAM) has been fabricated by the molecular beam epiiaxy (MBE) technique. Preliminary measurements show that our QD-SAM is a very promising candidate for passive mode-locking a fiber laser or a solid state laser with wavelength in the range of 970-1090nm. The 22%-33% dips in the reflectivity spectrum are observed, which are attributed to quantum dot absorption, indicating the potential for a large modulation
depth and hence generation of ultra-short laser pulses through mode-locking.
Photoluminescent nanostructured thin films have been fabricated using physical vapour deposition and the glancing angle deposition (GLAD) technique. Precision controlled substrate motion and oblique incidence (>75o) enable the fabrication of a variety of 3-D morphologies including vertical posts, helical (chiral) columns and chevrons. Scanning electron microscopy and X-ray diffraction were used to characterize the film nanostructure. These experiments focussed on the chiral morphology which exhibits intriguing polarization behaviour such as selective transmission of circularly
polarized light and circularly polarized photoluminescence. Helical films of Y2O3:Eu and Alq3 were fabricated with thicknesses in excess of 2 μm and densities nominally 60% of bulk. Transmission spectroscopic ellipsometry measurements were used to determine the degree of selective transmission of polarized light through the samples. The degree of circular polarization for the photoluminescent light emitted from helical films was measured with the use of a quarter waveplate and linear polarizer. Polarized photoluminescence efficiencies were consistent with the observed selective transmission of circularly polarized light through the films. The use of GLAD to control the nanoscale morphology of the films allows for the spectral location and strength of these polarization effects to be easily and accurately selected.
Nanostructured europium-doped yttrium oxide (Y2O3:Eu) films were fabricated using electron beam evaporation, in combination with the Glancing Angle Deposition (GLAD) technique. GLAD makes use of controlled substrate motion during physical vapour deposition (PVD) of a thin film resulting in a high degree of control over the nanostructure of the film. Films were deposited using pre-doped Y2O3:Eu source material. Scanning electron microscopy was used to characterize film nanostructure, while the light emission properties of these films were characterized by photoluminescence measurements. Films of four different nanostructures were used in this study: chevrons, pillars, helices, and normally-deposited solid thin films. For each film nanostructure, measurements of the angular dependence of the intensity of the emitted light, as well as absolute brightness, were obtained and compared. The polarization of the light emitted from the chevron film was also examined using a linear polarizer to analyze the polarization state. Measurements of the selective transmission of circularly polarized light through the helical samples were obtained using variable angle spectroscopic ellipsometry.
Thin films of europium-doped yttrium oxide (Y2O3:Eu), a well-known luminescent material, were grown using electron beam evaporation, in combination with the Glancing Angle Deposition (GLAD) technique. GLAD makes use of controlled substrate motion during physical vapour deposition (PVD), resulting in a high degree of control over the nanostructure of the film. Until recently GLAD had not been used with luminescent materials. Films were deposited using pre-doped Y2O3:Eu source material, with either 4.0% (wt) Eu doping or 5.6% (wt) Eu doping. The nanostructure of these films was characterized through scanning electron microscopy, while the light emission properties of these films was characterized by photoluminescence measurements. In order to optimize the light emission properties of the films the partial pressure of oxygen during the deposition of the films was varied. Films were deposited on both silicon and sapphire substrates, in order to compare how different substrates affect the growth and light emission of the films.
The capabilities of laser-induced breakdown spectroscopy (LIBS) for analysis of water samples with low energy laser pulses was investigated using 355 nm, 10 ns pulses with energies from 3.5 to 100 mJ. In order to optimize the detection limit, the spatial and temporal dependence of the line emission from a sodium solution water jet target in air has been measured, allowing the identification of optimum gating time and observation position for sodium. Careful characterization of the background noise sources in the LIBS detection system has been undertaken, including the continuum emission from the plasma, dark current in the detector array and electron emission noise in the image intensifier. The energy dependence of the limit of detection for sodium in water has been investigated. Single shot detection limits for sodium have been measured ranging from 2 ppm to 200 ppm for laser pulse energies of 100 mJ to 3.5 mJ respectively. For aluminium, the detection limits are over an order of magnitude poorer than for sodium.
In this paper we explore laser induced breakdown spectroscopy (LIBS) at relatively low energies in the range 10 -
350 tJ. We present measurements ofthe threshold laser energy needed for LIBS and the scaling ofplasma size and crater
size with energy. The effects of the laser pulse length and gating of the detector on the LIB spectra are studied and we also
assess the use ofmicrojoule LIBS for the identification ofAl alloys.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.