This PDF file contains the front matter associated with SPIE Proceedings Volume 8104, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Nanotechnology, in particular nanophotonics, is proving essential to achieving green outcomes of sustainability and renewable energy at the scales needed. Coatings, composites and polymeric structures used in windows, roof and wall coatings, energy storage, insulation and other components in energy efficient buildings will increasingly involve nanostructure, as will solar cells. Nanostructures have the potential to revolutionize thermoelectric power and may one day provide efficient refrigerant free cooling. Nanomaterials enable optimization of optical, opto-electrical and thermal responses to this urgent task. Optical harmonization of material responses to environmental energy flows involves (i) large changes in spectral response over limited wavelength bands (ii) tailoring to environmental dynamics. The latter includes engineering angle of incidence dependencies and switchable (or chromogenic) responses. Nanomaterials can be made at sufficient scale and low enough cost to be both economic and to have a high impact on a short time scale. Issues to be addressed include human safety and property changes induced during manufacture, handling and outdoor use. Unexpected bonuses have arisen in this work, for example the savings and environmental benefits of cool roofs extend beyond the more obvious benefit of reduced heat flows from the roof into the building.

The planar interface of a metal and a dielectric material can guide multiple surface-plasmon-polariton (SPP) waves-all of the same frequency, but different phase speed, attenuation rate, and spatial profiles of fields- provided that the dielectric material is periodically nonhomogeneous in the direction normal to the interface. Theoretical and experimental research during the last four years have validated this idea, thereby engendering the research area of surface multiplasmonics.7

We demonstrate a novel fabrication approach for high-throughput fabrication of engineered plasmonic antenna arrays and metamaterials with Nanostencil Lithography (NSL). NSL technique, relying on deposition of materials through a shadow mask, offers the flexibility and the resolution to fabricate radiatively engineer nanoantenna arrays for excitation of collective plasmonic resonances. We confirmed that the antenna arrays fabricated by NSL shows high optical quality similar to EBL fabricated ones. Furthermore, we show nanostencils can be reused multiple times to fabricate selfsame structures with identical optical responses repeatedly and reliably. This capability is particularly useful when highthroughput replication of the optimized nanoparticle arrays is desired. In addition to its high-throughput capability, NSL permits single step nanofabrication of plasmonic devices on surfaces that are difficult to work with electron/ion beam techniques. Nanostencil lithography is a resist free process thus allows the transfer of the nanopatterns to any planar substrate whether it is conductive, insulating or magnetic. As proof of the versatility of the NSL technique, we show fabrication of plasmonic structures and metamaterials in variety of geometries. In metamaterial and plasmonic devices, unique geometries with small gaps and asymmetries can induce novel electromagnetic responses such as plasmon induced transparency and also giant near-field intensities that are important for enhanced vibrational spectroscopy and non-linear optics applications. This nanofabrication scheme, enabling the reusability of stencil and offering flexibility on the substrate choice and nano-pattern design could significantly enhance wide-use of plasmonics in sensing technologies.1

We have investigated the heat generation from gold nanoparticles resulting from their local plasma resonance. The selfassembly of Au nanoparticle arrays/dielectric layer/Ag mirror sandwiches, namely, local plasmon resonators, have been demonstrated by using a dynamic oblique deposition technique. Due to strong interference, the optical absorption of the local plasmon resonator chips we prepared is successfully controlled between 0.0% and 97% in the near-infrared region, by changing the thickness of the dielectric layer. We evaluated the heat generation from Au nanoparticles by measuring the temperature of water with which a cell prepared on a chip was filled under laser illumination. The temperature increase of the water is proportional to the optical absorption of the local plasmon resonator chips. This suggests that the photothermal conversion efficiency can be controlled by interference. In order to show the temporal controllability of heat generation, we also demonstrated photoacoustic measurements. The acoustic signal from the local plasmon resonator chips was much larger than the signal not only form high reflective Ag thin film but also from the graphite. These features indicate that the local plasmon resonators are suitable for nanoheaters which are capable of spatio-temporal control.

Surface differential reflectance spectroscopy (SDRS), an optical characterization technique, is sensitive enough to observe the minute changes in the surface plasmon resonance (SPR) of noble metal nanoparticles (NPs). This SPR, which causes a sharp absorption of light in the visible range, is extremely sensitive not only to the morphology and organization of the NPs, but also to the chemical atmosphere surrounding them. Hence, taking SPR as a signature phenomenon, we have studied the reactivity of Ag NPs using a dedicated in situ SDRS set-up mounted on a magnetron sputtering machine. Real-time optical characterizations were possible not only during the deposition of Ag NPs, but also during their exposure to gases such as O₂, N₂, Ar, either non-ionized or partially ionized. This optical study reveals that Ag NPs are reactive to non-ionized O₂ exposure, which induces modifications in the SPR characteristics (width, amplitude and position of the absorption band) in contrast to N₂ and Ar. Moreover, this study also evidences a complete disappearance of the SPR when Ag NPs are exposed to partially ionized oxygen species O₂⁽⁺⁾ as well as a significant reactivity of the NPs exposed to N₂⁽⁺⁾, while Ar remains non-reactive in both non-ionized and partially ionized forms.

The theory of "classical" optical interference coatings is based on assumptions like ideal homogeneity and isotropy of the materials, as well as absolutely smooth and infinitesimally thin interfaces between the individual coating materials. Within the framework of these assumptions, there exists an elaborated theoretical apparatus for solving design and characterization tasks for optical coatings. At the same time, coating deposition techniques have been perfected in order to match with the requirements of homogeneity and smoothness of these coatings in practice. Remaining discrepancies between the theoretically predicted and practically achieved coating performance can - at least partially - be attributed to the violation of the above-mentioned ideal assumptions. But a closer look on this matter reveals a more differentiated picture: Nanostructure effects can be tackled as additional degrees of freedom for coating design, and can lead to useful property combinations that are inaccessible to "classical" coatings prepared on the basis of the traditionally available coating materials. This presentation deals with practical examples, where explicit violations of the usually assumed perfect homogeneity and smoothness of the coatings have resulted in novel and innovative coating material properties or coating designs. Examples include: - Effects of noble metal islands embedded in semiconductor films: applications in photovoltaics - Antireflection effects of nanostructured surfaces: motheye-structures - Effects of nanoporosity in oxide films on refractive index, thermal shift and mechanical stress: balanced coating properties The examples demonstrate the possible benefits of the exploitation of nanostructure-caused effects in interference coating science and technology.

This work presents a wide angle phase retarder by using a single anisotropic Ta₂O₅ columnar thin film. The single anisotropic Ta₂O₅ columnar thin film can provide phase retardation between two tangential eigenvectors to modulate the polarization state of light reflected from the prism-coupling system (BK7 prism/anisotropic thin film/air). In experiment, glancing angle deposition technique is used to prepare single layer film of Ta₂O₅ tilted nanorod array with thickness 270nm. In this analysis, we use wave tracing based on the Berreman calculus to calculate the variations of phases of eigen-waves in the anisotropic thin film as the electromagnetic wave is incident to the prism-coupling system. The uniform phase retardation can be observed in a wide angle range. A linearly polarized incident ray can be reflected as a specific elliptical polarized ray uniformly over the range. Similarly, the wide angle and broadband polarization conversion reflectance with high efficiency also exists in the single anisotropic Ta₂O₅ columnar thin film. The single anisotropic Ta₂O₅ columnar thin film can be useful for the further application in optical components design.

We discuss optical properties of ultrathin metal films, with particular attention to the phenomenon of quenched transmission. Transmission of light through an optically ultrathin metal film with a thickness comparable to its skin depth is significant. We demonstrate the quenched transmission through the ultrathin metal films when they are periodically modulated. We also discuss the physics behind it and explain how this abnormal phenomenon is ascribed to surface plasmon resonance effects.

In this paper, we present numerical and experimental results on optical properties of a multi-resonant UT-shaped plasmonic nanoaperture antenna for enhanced optical transmission and near-field resolution. We propose different structure designs in order to prove the effect of geometry on resonance spectrum and near-field enhancement. Theoretical calculations of transmission spectra and field distributions of UT-shaped nano-apertures are performed by using three-dimensional finite-difference time-domain method. The results of these numerical calculations show that transmission through the apertures is indeed concentrated in the gap region. In addition to theoretical calculations, we also performed a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography (EBL) and reactive ion etching in order to fabricate UT-shaped nanostructures. For further confirmation of the multiresonant behavior, we checked the individual U-and T-shaped nano-aperture antenna responses. We also studied the parameter dependence of the structure to determine the control mechanism of the spectral response. Theoretical calculations are supported with experimental results to prove the enhanced field distribution and multi-resonant behavior which can be suitable for infrared detection of biomolecules, wavelength-tunable filters, optical modulators, and ultrafast switching devices.teInp

In this work, the birefringence of bideposited symmetric nanorod array is investigated. The Ta₂O₅ nanorod arrays composed of several subdeposits are fabricated by serial bideposition (SBD) technique. Each nanorod consists of several identical units and each unit consists of symmetrical sections ABA. From the lateral view of the structure, the nanorod array is a symmetrical multilayered. The deposition planes for layer A and layer B are perpendicular to each other. For normal incident ray, the polarization-dependent refractive indices and phase thicknesses of the film are presented as functions of wavelength and optical constants of each layer. The transmittance spectra of symmetrical sections have a pass band property as the equivalent refractive indices are real. The principal indices of the Ta₂O₅ nanorod arrays with each subideposition thickness of 3 nm associated with the two orthogonal polarizations are measured by ellipsometer when the deposition angle is changed from 70° to 80°. According to principal indices database, a uniform phase retardation between the two orthogonal polarization directions can be designed for a specific wavelength range.

Properties of metamaterials are usually discussed in terms of biaxial anisotropic material parameters. To consider the underlying constitutive relations as valid, it is required that only weak spatial dispersion occurs. At operational frequencies of optical metamaterials this assumption often ceases to be valid. A description using effective material properties tends to be inadequate and new approaches are required. We outline here our latest achievements along this direction and discuss two approaches. The first one assumes that if it is not possible to introduce useful effective properties, a more primary source of information should be used to quantify metamaterials, leading to a characterization of metamaterials in terms of Jones matrices. We discuss the implications of this description and show that all metamaterials can be categorized into five classes, each with distinct properties. The second approach resorts to an effective description but restricts its considerations to a dispersion relation, characterizing the propagation of light in bulk metamaterials, and an impedance, characterizing the coupling between metamaterials and their surroundings. Definitions of both properties linked to a single Bloch mode are discussed and metamaterials are introduced which can be homogenized while considering only this single mode.

The investigation of the far-field radiation from a dipole source inside an infiltrated chiral sculptured thin films (CSTF) was extended to consider different positions of the dipole source and the presence or absence of fluid above the CSTF. From numerical studies, we found that within one structural period, the far-field radiation pattern varies as the source position varies and the pattern approximately repeats when the source is moved by one structural period. The intensity of the emitted radiation is less influenced by the presence of fluid above the CSTF. When the source is placed at the centre of the CSTF, the right circular polarization radiation is preferentially emitted through upper face of the CSTF whereas left circular polarization radiation is preferentially emitted through lower face.

The homogenization of arrays of metallic rods was studied. Using standard homogenization theory, the effective permittivity was obtained. The onset of resonances was evidenced and showned to be linked with the negative sign of the real part of the permittivity. Numerical computations were performed to test the homogeneous model.

Nano-sculptured thin films (STF) are prepared by the glancing angle deposition technique and take different forms of nano columnar structures. Varieties of STFs are investigated to find the optimum structure for biosensing based on the surface enhanced fluourescence (SEF). The highest amplification of fluorescent signal is found for Ag based STFs on fused silica giving an enhancement factor of x23°, where h=400nm, d=75nm, á=23o relative to Ag dense film using fluorescent dye Rhodamine 123. Based on this, a demonstration of monitoring of antibodies and even confirmation of successful immobilization of the receptors presented. Bound antibody to the thiol self assembly monolayer on sample surface is then quantified by means of the fluorescent signal. Upon excitation of the fluorophore by Hg source light, a CCD camera with a controlled exposure time detects the pattern of fluorescent antibody/E-coli bacteria colonies on the STF surface. A fiber optic holder attached to the microscope allowed quantitative measurement of the fluorescence spectrum on a microspot.

We study the effect of different surface functionalization methods on the sensing performances of porous silicon (PSi) microcavities when used for detection of biomolecules. Previous research on porous silicon demonstrated versatility of these devices for sensor applications based on their photonic responses. The interface between biological molecules and the Si semiconductor surface is a key issue for improving biomolecular recognition in these devices. PSi microcavities were fabricated to reveal reflectivity pass-band spectra in the visible and near-infrared domain. To assure uniform infiltration of proteins the number of layers of Bragg mirrors was limited to five, the first layer being of high porosity. In one approach the devices were thermally oxidized and functionalized to assure covalent binding of molecules. Secondly, the as etched PSi surface was modified with adhesion peptides isolated via phage display technology and presenting high binding capacity for Si. Functionalization and molecular binding events were monitored via reflectometric interference spectra as shifts in the resonance peaks of the cavity structure due to changes in the refractive index when a biomolecule is attached to the large internal surface of PSi. Improved sensitivity is obtained due to the peptide interface linkers between the PSi and biological molecules compared to the silanized devices. We investigate the formation of peptide-Si interface layer via X-ray photoelectron spectroscopy, scanning tunneling microscopy and scanning electron microscopy.

Mesoporous silicon (PS) is used as matrix for infiltration of Fe₃O₄ nanoparticles (5 and 8 nm). The structure and magnetic behaviour of such composites are investigated and a correlation between the morphology of the nanocomposite (structure of the matrices, size and distribution of Fe₃O₄ particles) and the magnetic properties of the system is figured out. This system shows a superparamagnetic (SPM) behaviour at room temperature and becomes ferromagnetic (FM) at lower temperatures. The transition temperature between SPM and a blocked state depends on the particle size, their coating and on their magnetic interactions. Dipolar coupling between the particles can be influenced by varying the PS morphology as well as by the filling factor. The blocking temperature (T_B) of the composite is tuneable and changes due to the variation of dipolar coupling of the Fe₃O₄-particles (distance between particles). Results gained from electron microscopy and tomography, respectively such as size and spatial distribution of the particles together with the magnetic data lead to a more detailed knowledge of the Fe₃O₄/silicon nanocomposite system.

In this work nanostructured porous silicon (nanoPS) was used for the fabrication of surface micropatterns aiming at controlling cell adhesion and migration. In particular, surface patterns of nanoPS and Si were engineered by high-energy ion-beam irradiation and subsequent anodization. It was found that human skeletal progenitor cells are sensitive to oneand two-dimensional patterns and that focal adhesion is inhibited on nanoPS areas. In spite of this anti-fouling characteristics, studies on patterns with reduced Si areas show that cells conform to nanoPS pathways favoring migration through cell protrusion, body translocation and tail retraction from two parallel Si traction rails. Moreover, migration can be blocked and cells tend to arrange when grid patterns with the appropriate dimensions are fabricated. The experimental results confirm that progenitor cells are able to exploit nanoPS anti-fouling designs by adapting to it for migration purposes.

Metal-nanostructures are electrochemically deposited within the pores of porous silicon to achieve a hybrid material with specific magnetic properties. The metal structures can be precipitated with various geometries and different spatial distributions depending on an accurate control of the deposition conditions. This method allows to deposit structures as spheres, ellipsoids or wires with a size up to a few micrometers whereas the diameter corresponds to the pore-diameter. Furthermore small Ni-particles between 3 and 6 nm can be deposited in a densely packed arrangement on the pore walls forming a quasi metal tube. Analysis of this tube-like arrangement by transmission electron microscopy shows that the distribution of the Ni-particles is quite narrow, which means that the distance between the particles is smaller than 10 nm. Such a close arrangement of the Ni-particles assures magnetic interactions between them. Due to their size these small Ni-particles are superparamagnetic but dipolar coupling between them results in a ferromagnetic behaviour of the whole system. Moreover, to investigate the interface between the materials in more detail electron energy loss spectroscopy is employed. Magnetic measurements show an anisotropy between easy axis and hard axis magnetization which corresponds to the behaviour of a metal tube. This composite is an interesting candidate for integrable magnetic and magneto-optic devices and also for spin-injection from a ferromagnetic metal into silicon.

In this work, we investigate magnetic responses in various Ag-SiO₂-Ag nanosandwich structures at visible wavelengths. The two electric resonant modes corresponding to the in-phase (symmetric) and anti-phase (asymmetric) electric dipole on the top and the bottom nanopillars are observed by the finite difference time domain (FDTD) simulation. In the asymmetric resonant mode, the phases of electric fields oscillating in the top and bottom pillars have opposite directions, leading to a virtual current loop that induces the magnetic field reversal. The nanosandwich structure produces a large enhancement of the magnetic field as the thickness of SiO₂ nanopillar is much smaller than wavelength. By increasing the diameter of nanopillars from 150 nm to 250 nm, the inverse magnetic response wavelength shifts from 532 nm to 690 nm. On account of the magnetic field reversal caused by the anti-phase electric dipole coupling, the real part of the equivalent permeability of the film is negative. Therefore, the wavelength range associated with the intensity of inverse magnetic response is tunable by varying the size of Ag-SiO₂-Ag nanosandwich structure. The equivalent electromagnetic parameters of the Ag-SiO₂-Ag nanosandwich thin film prepared by glancing angle deposition are derived from the transmission and the reflection coefficients measured by walk-off interferometers. The measured results indicate that film exhibit double negative properties and lead to negative values of the real parts of equivalent refractive indices -0.854, -1.179, and -1.492 for λ = 532 nm, 639 nm, and 690 nm, respectively. Furthermore, the real part of permeability is negatively enhanced to be -4.771 and the maximum value of figures of merit (FOM) recorded being 6.543 for p-polarized light at λ = 690 nm. Finally, we analyze the admittance loci for our nanosandwich thin film. This analysis can be applied to interpret extraordinary optical properties such as negative index of refraction from Ag-SiO₂-Ag nanosandwich films.

Atomic shadowing during physical vapor deposition causes exacerbated growth of surface protrusions and leads to a chaotic 3D layer growth, which can result in the development of well-separated nanorods, nanosprings, or nanopipes, which are surprisingly regular and have potential applications ranging from fuel cell electrodes and pressure sensors to self-lubricating coatings and nanoactuation. Glancing angle deposition (GLAD) causes particularly strong atomic shadowing and can be used to systematically investigate the effect of shadowing on the morphological evolution. These extremely rough layers cannot be described as a chaotic perturbation from a flat surface. However, using a model which describes them as a nanorod array with an average rod width that follows power law scaling results in experimental curves where all metals converge on a single master curve which exhibits a discontinuity at 20% of the melting point, associated with a transition from a 2D to a 3D island growth mode, and a single homologous activation energy of 2.46 for surface diffusion on curved nanorod growth fronts, which is applicable to all metals at all temperatures. Also, under extreme shadowing conditions, the conventional structure zone model is simplified as there is a direct transition from an underdense (zone I) to a dense (zone III) structure at ~50% of the melting point.ïýc

Thin films of Cu-In composite nanoparticles were produced by electrophoretic deposition in colloidal suspensions. The nanoparticles were prepared with high power pulsed laser ablation in liquid solvents. The nanoparticles inherited composition (Cu/In ratio) from the target during laser ablation. The colloidal suspension was stable against agglomeration without adding additional surfactant or dispersing agent. The success of electrophoretic deposition of the nanoparticles was explained based on electrochemical interactions between the nanoparticles and the electrode. CuInSe₂solar absorber layers were produced after annealing the thin films in selenium vapor under atmospheric pressure. Solar cell devices were made on Mo metal sheet and Mo-coated soda-lime glass substrates with an energy conversion efficiency of up to 3.4% under AM1.5G illumination. The results open up a new route of non-vacuum fabrication of thin film chalcopyrite solar cells on flexible substrates with minimized chemical contamination, easy compositional control, and high raw material utilization.ationDa

Al-doped ZnO can replace tin-doped indium oxide (ITO) as a good transparent conductive oxide (TCO) in LEDs and optoelectronic applications. We investigate on nanometer scale AlZnO thin film materials epitaxied on sapphire substrates in 350-650°C from pulsed laser deposition (PLD). Synchrotron radiation X-ray absorption fine-structure spectroscopy on O K-edge indicates that Al-doped ZnO can not form alloy at growth temperature 350°C without Al-O bonding feature. The Al-O transition of AZO550 is stronger than AZO650. These are correlated to Raman scattering measurements and analyses. Al-doped ZnO grown at 350°C possesses weak/broad Raman signals indicating a poor crystalline film. The E2 (high) mode is strong and narrow in AZO550. All these experimental results indicate that PLD grown AlZnO film on sapphire could get a better crystalline quality at 550°C than 350°C and 650°C.

Luminescent biocellulose membranes were obtained by incorporation of ethanolic solutions of the europium compounds [Eu(BTFAC)3(H2O)2], [Eu(BTFA)₃(DBSO)₂], [Eu(BTFA)₃(PTSO)₂] and [Eu(BTFA)₃(FSO)₂] (BTFAC- 4,4,4-Trifluoro-1- phenyl-1,3-butanedione DBSO- dibenzyl sulfoxide, PTSO- p-Tolyl sulfoxide and FSO- phenyl sulfoxide). Selfsustainable semi-transparent composite membranes were obtained showing strong emission under UV exctiation. The antenna hole played by the ligands was observed to be more efficient in the composite membranes than in the precursor complexes which by themselves are also strong red emitter compounds. These new multifuctional membranes could find application in different areas as phosphors and UV→Visible energy converting devices.

We investigate the effects of three reduction processes on the formation of silver nanoparticles in mesoporous titania films. The later are impregnated with silver salt and then either exposed to UV laser light, chemically treated or annealed. Depending on the reduction process, the NP are confined inside the mesopores or not, leading to different NP size distributions and to various film colors. These TiO₂/Ag nanocomposite films also exhibit different photochromic behaviours when exposed to visible laser radiations. We characterize and interpret the color changes as well as the NP deformation and oxidation under visible illuminations.

Nanostructured carbon materials have increasingly attracted the interest of the scientific community, because of their fascinating physical properties and potential applications in high-tech devices. In the current ITER design, the tiles made of carbon fiber composites (CFCs) are foreseen for the strike point zone and tungsten (W) for other parts of the divertor region. This choice is a compromise based mainly on experience with individual materials in many different tokamaks. Also Beryllium is the candidate material for the First Wall in ITER. In order to prepare nanostructured carbon-tungsten nanocomposite for the divertor part in fusion applications, the original method thermionic vacuum arc (TVA) was used in two electronic guns configuration. One of the main advantages of this technology is the bombardment of the growing thin film just by the ions of the depositing film. The nanostructured C-W and C-Be films were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The C-W films were identified as a nanocrystals complex (5 nm average diameter) surrounded by amorphous structures with a strong graphitization tendency, allowing the creating of adherent and wear resistant films. The C-Be films are polycrystalline with mean grain size about 15 nm. The friction coefficients (0.15 - 0.35) of the C-W coatings was decreased more than 3-5 times in comparison with the uncoated substrates proving excellent tribological properties. C-W nanocomposites coatings were designed to have excellent tribological properties while the structure is composed by nanocrystals complex surrounded by amorphous structures with a strong graphitization tendency, allowing the creating of adherent and wear resistant films.&updat

We used the Langmuir-Blodgett (LB) method for preparation of defect-free and large-area silica-nanoparticlesmonolayer as a template for the fabrication of Au nanostructures on an Au-thinfilm for surface plasmon resonance (SPR). The dimensions of trigonal pyramid Au nanostructures were controlled by changing the particle size of the silica LB template. The nanostructured SPR chips provide the enhancement of sensitivity in SPR analysis compared to a conventional SPR chip when 20 % ethanol solution was used as an analyte. We took a theoretical approach by evaluating optical properties of the Au-nanostructures and nanostructured SPR chips in the view of plasmonic effect.

By using the Hot Filament Chemical Vapor Deposition (HFCVD) technique tungsten thin films were deposited on amorphous quartz substrates. To achieve this, a tungsten filament was heated at 1300 °C during 30 minutes maintaining a constant pressure inside the chamber at 460 mTorr and substrate at 700 °C. Transition from tungsten oxide deposits to tungsten thin films, by varying the substrate temperature, were characterized by means of Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), X-Ray Diffraction and, micro-Raman spectroscopy. The SEM micrographs reveal that the tungsten films have no more than 200 nm in thickness while XRD show evidence of the films crystallize in the á-tungsten modification. On the other hand, AFM shows that the tungsten thin films exhibit a uniform and smooth surface composed with semi-spherical shapes whose diameters are below than 50 nm. Furthermore, to the naked eye, the as-deposited tungsten films exhibit a high mirror-like appearance.

To develop diverse anisotropic thin films, asymmetric bideposition technique is introduced to fabricate tilt columnar Ta₂O₅ films with biaxial optical property. The asymmetric bideposition is achieved using two different opposite deposition angles (a₊,a_-) and two different thicknesses of opposite deposited subdeposits. The two sets of Ta₂O₅ columnar thin films associated with deposited subdeposits (d+,d-)=(5.2,2.8) are prepared at the opposite deposition angles (a₊,a_-)=(70,-40), (75,-40), (80,-40) and at the opposite deposition angles (a₊,a_-)=(70,-50), (75,-50), (80,-50). Columnar thin films with various column angle and biaxial properties are measured their planar birefringence and three principal indexes. The larger column angle leads to higher principal indices. It is demonstrated that the asymmetric bideposition can enhance the birefringence of a tilted columnar thin film.ntut.edu.tw