Proceedings Volume 7404

Nanostructured Thin Films II

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Proceedings Volume 7404

Nanostructured Thin Films II

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Volume Details

Date Published: 20 August 2009
Contents: 8 Sessions, 17 Papers, 0 Presentations
Conference: SPIE NanoScience + Engineering 2009
Volume Number: 7404

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7404
  • Optical Properties/Metamaterials
  • Nanostructure and EM
  • Semiconductors and Oxides
  • Polymers and Nanocomposites
  • Environmental and Solar
  • Structure/Sensing
  • Poster Session
Front Matter: Volume 7404
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Front Matter: Volume 7404
This PDF file contains the front matter associated with SPIE Proceedings Volume 7404, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
Optical Properties/Metamaterials
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Surface plasmon modes and their interactions in multilayer thin-film structures
Timothy J. Davis, Daniel E. Gómez, Kristy C. Vernon
The propagation of surface plasmons in thin films is important for a number of technologies and has found applications in chemical and biological sensing. There is growing interest in the use of surface plasmons coupled with optical systems for high density photonic devices. While the analysis of the properties of surface plasmons at a metal-dielectric interface is straightforward, it becomes increasingly more difficult as the number of surfaces is increased, as in a multi-layer thin film structure. In this paper we discuss recent developments in mathematical methods for studying the properties of surface plasmons in multi-layer thin film structures of the metal-insulator-metal (MIM) type. The films may consist of a large number of layers creating MIMIM... structures that determine the allowed modes of the surface plasmons. The mathematical formulation is based on a matrix method that yields the eigenvalues (dispersion relation) and the eigenfunctions (mode profiles) associated with the surface plasmons. The method is used to analyze modes in a number of structures. In particular it is shown that modes in structures that contain an optically resonant film can have dispersion curves that cross one another and that changing the resonances in the film can lead to switching of the surface plasmon modes.
Polarization properties of nano-structured thin films in reflection and transmission: a new theorem on polarized light
We prove a new theorem on polarized light: when un-polarized (natural) light is incident to a lossless optical element, the polarized reflected intensity equals the polarized transmitted intensity. We have confirmed the theory both through algebraic simulation and through experiments carried out on a Titanium Oxide chiral thin film.
Nanostructure and EM
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On limitations of conventional approaches to homogenization applied to uniaxial dielectric composite materials
Tom G. Mackay, Akhlesh Lakhtakia, Andrew J. Duncan
Under certain conditions, the Bruggeman formalism yields estimates of the effective constitutive parameters of homogenized composite materials (HCMs) which are physically implausible. Furthermore, under these conditions, the generalized Hashin-Shtrikman bounds (which are equivalent to the estimates of the effective constitutive parameters of the HCMs provided by the Maxwell Garnett formalism) exhibit strong resonances. The conditions are that (i) the real parts of the constitutive parameters of the constituent materials have opposite signs; and (ii) the constituent materials are weakly dissipative. These limitations - which we had previously established for isotropic dielectric HCMs - are shown to afflict uniaxial dielectric HCMs.
Comparisons of enhanced absorption in closely-coupled grating-mirror and random particle-mirror systems
The grating-mirror geometry is a particularly rich plasmonic system due to the coupling of localized and global modes, and it is applicable to negative index materials, plasmonic imaging, and spectral filters. Recently absorption in sub-percolative films was found to be greatly enhanced by the addition of a mirror - a situation that is also reasonably modeled by a grating-mirror geometry. A great deal of attention has been focused on the coupling of barely-sub-wavelength periodic grating modes to surface plasmon polaritons that exhibit sharp spectral features. In contrast, island films have only quasi-periodicity at a few tens of nanometers, and produce broader spectral features, suggesting the influence of localized surface plasmons. In this work we examine how absorption is affected by variations in geometry of grating-mirror systems, to identify basic physics for future investigations of particle-mirror systems.
Effective properties of resonant arrays of rods
Didier Felbacq, Guy Bouchitté, Christophe Bourel, et al.
The effective electromagnetic properties of a metamaterial made of nanorods are investigated. It is found that near inner resonances there is a effective magnetic behavior. The domain of validity of the effective permeability model is determined with respect to the wavelength and the filling ratio by means of rigorous numerical computations. It is concluded that the relative dielectric constant should be higher than 32 and the filling ratio lower than 1/2.
Semiconductors and Oxides
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Effects of oxygen on structural, morphological, and optical properties of sputtered ZnO films on glass substrate
Y. P. Liao, Sh. X. Li, J. H. Zhang, et al.
The structural, morphological and optical properties of zinc oxide (ZnO) thin films were investigated. The ZnO thin films were deposited on glass substrate at room temperature (RT) through radio frequency magnetron sputtering in different O2 flux (fixed Ar flux). The structural properties and morphology were studied by X-ray diffraction and atomic force microscopy, respectively. The highly crystallized ZnO thin films were obtained. It is found that all the films have preferential orientation in c-axis direction and the crystallinity of the films is strongly affected by O2 flux. The crystallinity is improved greatly when the film is annealed in O2 ambient. Atomic force microscopy results show that the films are compact and smooth. Near band edge emission peak in photoluminescence spectrum for the typical sample appears red-shift phenomena. All the films present a high transmittance of above 90% in the visible region.
Polymers and Nanocomposites
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Formation of polymer thin films and interface control by physical vapor deposition
Hiroaki Usui
Some strategies of physical vapor deposition (PVD) of polymer thin films have been proposed. Direct vapor deposition can be applied for simple polymers like polyethylene and Teflon. Coevaporation of bifunctional monomers can be achieved to deposit polyimide, polyurea etc., while chain polymerization assisted by ultraviolet or electron irradiation can be used to form vinyl or acryl polymers from single evaporation source. Surface-initiated deposition polymerization, which combines the self-assembled monolayer and vapor deposition, is another unique method to grow polymer thin films that are chemically bound to the substrate surface. The last method is also effective in controlling the interface between polymer films and inorganic substrates. The solvent-free nature of PVD is convenient for the formation of nanometer-thick films and especially multilayers that are required for device fabrication. Application of vapor deposition polymerization for fabrication of organic light-emitting diode is also described.
Thin film, nanoparticle, and nanocomposite fabrication by through thin film ablation
P. T. Murray, E. Shin
We have developed a laser-based technique for fabricating thin films, nanoparticles, and nanocomposite thin films. The process is denoted Through Thin Film Ablation (TTFA) and entails using a thin film target that is ablated from the backside. The deposits produced by this process show neither evidence of the larger (micrometer-sized) particles nor the extent of agglomeration that are produced by conventional laser ablation. The TTFA technique offers the potential for fabricating a wide variety of materials in thin film, nanoparticle, and nanocomposite form. In this paper we present the results of Fe nanoparticle synthesis by TTFA including nanoparticle size distributions, time of flight distributions, and time resolved spectral data. These data provide a more complete understanding of the TTFA process.
Mechanical properties of epoxy nanocomposites reinforced with very low content of amino-functionalized single-walled carbon nanotubes
Yun Zhao, Haiping Hong, Jeffry S. Welsh
Functionalized single-walled carbon nanotubes (SWNTs) with amino groups were prepared by oxidation, acylation, and amidation of SWNT surfaces. Epoxy/SWNT composite membranes were fabricated using a very low content of amino-grafted SWNTs (≤0.08wt%) as fillers. SWNTs with amino groups acted as a curing agent, covalently bonding to the epoxy matrix. The influence of SWNT content on the mechanical properties of epoxy/amino-functionalized SWNT composite membrane was investigated. It is found that the tensile strength of composites is enhanced with the increase of SWNTs. Only 0.01wt% of SWNT-R-NH2 leads to improvement of the epoxy tensile strength by 9.5%, and 0.08wt% of SWNT-R-NH2 increased tensile strength by 13.6%. For comparison purposes, epoxy/pristine-SWNT films were also prepared. The improvement of the tensile strength of the amino-functionalized SWNTs system is more remarkable than that of pristine SWNT system at very low weight-percentage loading. The amino groups on the surface of SWNTs can be covalently attached to the epoxy matrix, which effectively improves the dispersion and adhesion of SWNTs in epoxy. This leads to the enhancement in mechanical properties of the epoxy composite. Mechanical results between functionalized and pristine nanotubes are discussed in detail.
Environmental and Solar
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Angular selectivity: impact on optimised coatings for night sky radiative cooling
To achieve strong net thermal radiation emission from surfaces whose temperature is at or below ambient it is important to have high absorptance between 7.9 μm to 13 μm where the atmosphere is most transparent. Outside of this band the atmosphere behaves like a black body emitter and hence at these wavelengths net radiant heat loss is normally not possible at sub-ambient temperatures. It becomes possible using two types of angular selectivity, which also improve emission between 7.9 μm to 13 μm. One is coating based, and one uses external heat mirrors. In the latter low emittance mirrors replace the higher emitting segments of the atmosphere. The coating's net gain is a result of its reflectance rise countering the atmosphere's drop in transparency as ray angles to the zenith approach the horizontal. These ideas are examined in the context of experimental data on coatings which rely on nanostructure to largely limit their spectral absorption to the atmosphere's transparent band. The angular selective coating becomes possible in two multilayer types (a) one nano-layer is strongly reflective (b) one layer has much higher index than the other. Type (a) materials as nanoparticles provide surface phonon resonance in the desired absorption band.
Structure/Sensing
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Biomimetic materials processing
Takahiro Ishizaki, Junko Hieda, Maria A. Bratescu, et al.
A biomimetic super-hydrophobic/super-hydrophilic micro-patterned surface was successfully fabricated by microwave plasma enhanced chemical vapor deposition (MPECVD) and vacuum ultraviolet (VUV) light lithography. On the micropatterned surface, various site-selective immobilizations were carried out. The fluorescent polystyrene spheres and copper were deposited site-selectively on super-hydrophobic regions using electrostatic interactions. The micropatterned surface brought the discrete adhesions of E. coli and B. subtilis specifically on super-hydrophobic regions. On the other hand, NIH 3T3 fibroblast cells attached to the super-hydrophilic regions in a highly selective manner.
Development of electrical biosensors based on nanostructured porous silicon
G. Recio-Sánchez, M. Manso, V. Torres-Costa, et al.
Nanostructured porous silicon (nanoPS) can be described as a network of silicon crystals with sizes in the range of a few nanometers. The typical large specific surface area and high reactivity of nanoPS make this material very suitable for many different applications in the field of sensing. Moreover, its biocompatibility and biodegradability opens the way to the development of biosensors. Within this context, in the present work the use of nanoPS in the field of electrical biosensing is explored. More specifically, nanoPS-based devices with the structure Al/nanoPS/silicon/Al and AuNiCr/nanoPS/silicon/Al were fabricated for the electrical detection of glucose and the bacteria Escherichia Coli. The experimental results show that the current-voltage characteristics of the metal/nanoPS/silicon/metal structures show a strong dependence on the presence/absence and surface concentration of glucose and the bacteria Escherichia Coli. The present work describes our findings in the correlation between surface concentration of glucose and bacteria E. Coli and current for a given voltage.
High temperature XRD of zirconia/alumina multilayer thin films prepared by pulsed laser deposition
G. Balakrishnan, S. Murugesan, C. Ghosh, et al.
Al2O3/ZrO2 multilayers have been deposited on Si(100) substrates by reactive pulsed laser deposition technique. The experiments were performed at an optimized oxygen partial pressure of 3x10-2 mbar at room temperature. A nanolaminate structure consisting of alternate layers of ZrO2 and Al2O3 with 40 bi-layers were fabricated with thickness of each layer of zirconia and alumina of 15 nm and 5 nm, respectively. The cross-sectional transmission electron microscope (XTEM) investigations were carried out on a multilayer thin film deposited at room temperature. The XTEM study shows the formation of uniform thickness, higher fraction of monoclinic and small fraction of tetragonal phases of zirconia and amorphous alumina. The ZrO2 /Al2O3 multilayer film was characterized using high temperature x-ray diffraction (HTXRD) in the temperature range RT-1473 K. The ZrO2 /Al2O3 multilayer shows a crystallization temperature of 673 K for the formation of tetragonal and monoclinic phases with significant amount of tetragonal phase over the latter. From the HTXRD profiles, crystallite size, lattice parameters, and thermal expansion coefficient of the tetragonal phase were calculated.
Poster Session
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Optical and transport properties of nanostructured PbTe(In) films
Alexandr Dobrovolsky, Ivan Belogorokhov, Zinovi Dashevsky, et al.
Photoelectric, transport and optical properties are studied for nanostructured PbTe(In) films. Synthesis of the films was performed using evaporation of a target source to a glass substrate. The films have column-like structure with a mean grain size varying from about 60 nm to 170 nm depending on the substrate temperature. Analysis of the data obtained revealed that the conductivity of the films is determined by two mechanisms: charge transport along the inversion channels at the grain surface and activation through barriers at the grain boundary. Persistent photoconductivity appears in the films below T = 150 K. The frequency dependence of the relative photoresponse has a pronounced maximum. The photoresponse in the ac mode may be by two orders of magnitude higher than in the dc measurements.
Measurement of phase and amplitude modulations in Sb-based films
In this work we studied the changes of the optical constants of films in the binary system Sb2O3-Sb2S3 induced by light in the VIS-UV. The measurements were performed before and after homogeneous irradiation of the films to a Hg lamp and in real time during the holographic exposure of the samples (at 458nm). Changes of the absorption coefficient (amplitude grating) and refractive index (phase grating) were measured simultaneously using the self-diffraction using the holographic setup. Besides the films presented a strong photodarkening effect under homogeneous irradiation, the samples holographically exposed presented only refractive index modulations. None amplitude modulation was measured in real time for spatial frequencies of about 1000 l/mm.
Relationship between the contact angle and the tilt angle on the vertical polymer layer of NLC using various ion beam exposure energy
Ji-Hun Lim, Young-Hwan Kim, Byeong-Yun Oh, et al.
Recently, the relationship between surface energy and tilt angle on vertical polyimide (PI) was studied. The study showed that ion beam (IB) exposure using argon gas changes the surface energy of vertical PI as a function of exposure time. This characteristic induces the transition of vertical liquid crystal (LC) orientation from vertical to homogeneous. In this study, we applied the property to fabricate liquid crystal displays (LCD) with both vertical alignment (VA) and twisted nematic (TN) LCDs on vertical PI. The study revealed correlations between various IB exposure energies and surface energies with the same exposure time on vertical PI. X-ray photoelectron spectroscopic spectra were analyzed to prove the correlations and transmittance curves via applied voltage to VA, and TN LCDs were evaluated to observe the LC driving performance on IB-irradiated vertical PI.