This PDF file contains the front matter associated with SPIE Proceedings Volume 8818, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Nature has evolved objects with desired functionality using commonly found materials. Nature capitalizes on hierarchical structures to achieve functionality. The understanding of the functions provided by objects and processes found in nature can guide us to produce nanomaterials, nanodevices, and processes with desirable functionality. This article provides an overview of four topics: (1) Lotus Effect used to develop superhydrophobic and self-cleaning/antifouling surfaces with low adhesion, (2) Shark Skin Effect to develop surfaces with low fluid drag and anti-fouling characteristics, and (3-4) Rice Leaf and Butterfly Wing Effect to develop superhydrophobic and self-cleaning surfaces with low drag. Rice Leaf and Butterfly Wings combine the Shark Skin and Lotus Effects.

Inspired by nature, nano-textured surfaces have attracted much attention as a method to realize optical surface functionality. The moth-eye antireflective structure and the structural colors of Morpho butterflies are well- known examples used for inspiration for such biomimetic research. In this paper, nanostructured polymer surfaces suitable for up-scalable polymer replication methods, such as imprinting/embossing and injection-molding, are discussed. The limiting case of injection-moulding compatible designs is investigated. Anti-reflective polymer surfaces are realized by replication of Black Silicon (BSi) random nanostructure surfaces. The optical transmission at normal incidence is measured for wavelengths from 400 nm to 900 nm. For samples with optimized nanostructures, the reflectance is reduced by 50 % compared to samples with planar surfaces. The specular and diffusive reflection of light from polymer surfaces and their implication for creating structural colors is discussed. In the case of injection-moulding compatible designs, the maximum reflection of nano-scale textured surfaces cannot exceed the Fresnel reflection of a corresponding flat polymer surface, which is approx. 4 % for normal incidence. Diffraction gratings provide strong color reflection defined by the diffraction orders. However, the apperance varies strongly with viewing angles. Three different methods to address the strong angular-dependence of diffraction grating based structural color are discussed.

It is desired to have artificial optical materials with controllable optical properties. One approach is to create composite materials with nanomachining and nanostructures. In this research, two-dimensional (2D) nanostructures were created on the surface of optical glass using nanosphere lithography. The effective refractive index of the artificial layer is smaller than the refractive index of the substrate and can be varied by changing the size of the nanoparticles and depth of etching. In comparison with conventional techniques, this approach is more efficient and cost-effective for the creation of large areas of thin surface layers as an artificial material. A uniform monolayer of 200 nm polystyrene nanospheres was deposited on soda-lime glass slides. Deposition was performed via a slide-coating technique to take advantage of capillary forces. The slides were etched with vapor-phase hydrofluoric acid (HF) to create 2D structures. Vapor-phase etching was selected in order to etch the substrate without disturbing the monolayer nanoparticle mask. The etching rate of nanostructures was studied. An atomic force microscope (AFM) was used to monitor the nanosphere monolayers and etching analysis. It was shown that the nanoparticle pattern was successfully transferred to the surface of the substrate. The resultant thin-layer of modified substrate serves as an artificial material with a desired refractive index which modifies the surface reflection and transmission properties. The substrate with the created artificial material layer demonstrated reduced reflectivity in optical wavelengths.

SiC single-layer or multi-layer on C used to improve the oxidation resistance and tribological properties of C have been obtained by Thermionic Vacuum Arc (TVA) method. The 200nm thickness carbon thin films was deposed on glass or Si substrate and then 100÷500 nm thickness SiC successively layers on carbon thin film was deposed. The microstructure and mechanical characteristics of as-prepared SiC coating were investigated by Transmission Electron Microscopy (TEM, STEM), Energy Dispersive X-Ray Spectroscopy (EDS), Electron Scattering Chemical Analysis (ESCA) and tribological techniques. Samples containing SiC single-layer or multi-layer coating on carbon were investigated up to 1000°C. The results of thermal treatments reveals the increase of oxidation resistance with increase of the number of SiC layers. The mechanism of oxidation protection is based on the reaction between SiC and elemental oxygen resulting SiO₂ and CO. The tribological behavior of SiC coatings was evaluated with a tribometer with ball-on-disk configuration from CSM device with 6mm diameter sapphire ball, sliding speed in dry conditions being 0.2m/s, with normal contact loads of 0.5N, 1N, 1.5N and 2N, under unlubricated conditions. The friction coefficient on SiC was compared with the friction coefficient on uncoated carbon layer. Electrical surface resistance of SiC coating on carbon at different temperatures was measured comparing the potential drop on the sample with the potential drop on a series standard resistance in constant mode.

The homogenization of arrays of rods was studied. By means of an asymptotic analysis, a simplified form of the transfer matrix was obtained.

The optical resonances that occur in nanostructured metal layers are modulated in thin film stacks if the nanostructured layer is separated from a reflecting conducting layer by various thicknesses of thin dielectric. We have measured and modeled the optical response of interacting silver layers, with alumina spacer thickness ranging from a few nm to 50 nm, for s- and p-polarized incident light, and a range of incident angles. Standard thin film models, including standard effective medium models for the nanostructured layer, will break down for spacer thickness below a critical threshold. For example, with polarisation in the film plane and some nano-islands, it may occur at around 10 nm depending on spacer refractive index. Of particular interest here are novel effects observed with the onset of percolation in the nanolayer. Hot spot effects can be modified by nearby mirrors. Other modes to consider include (a) a two-particle mode involving a particle and its mirror image (b) A Fano resonance from hybridisation of localized and de-localised plasmon modes (c) a Babinet’s core-(partial) shell particle with metal core-dielectric shell in metal (d) spacing dependent phase modulation (e) the impact of field gradients induced by the mirror at the nano-layer.

In the nonsingular case of optical propagation in a linear, homogeneous, anisotropic, dielectric material, two independent plane waves, with orthogonal polarizations and different phase speeds, can propagate in a given direction. However, in certain dissipative biaxial materials there are particular directions along which these two waves coalesce to form a single plane wave. This coalescent Voigt wave represents the singular case. Most conspicuously, the amplitude of Voigt waves are linearly dependent upon propagation direction. A porous nanostructured thin film which supports Voigt wave propagation was investigated, with a view to possible optical sensing applications. The directions along which Voigt waves propagate can be highly sensitive to the refractive index of a fluid which infiltrates this porous material. Indeed, in our theoretical studies sensitivities which compare favourably to those of surface-plasmon-polariton-based optical sensors were found.

Propagation characteristics of optical fibers are greatly dependent on materials, which the guides are comprised of. Varieties of materials have been developed and investigated for their usage in fabricating optical fibers for specific applications. Within the context, a liquid crystal medium is both inhomogeneous and optically anisotropic, and fibers made of such mediums are greatly useful. Also, liquid crystals exhibit strong electro-optic behavior, which allows alternation in their optical properties under the influence of external electric fields. These features make liquid crystal fibers greatly important for optical applications. The present communication is aimed at providing a glimpse of the efficacy of liquid crystals and/or fibers made of liquid crystals, followed by the analytical investigation of wave propagation through such guides. The sustainment of modes is explored in these fibers under varying fiber dimensions, and the novelty is discussed. The case of tapered liquid crystal fibers is also briefly discussed highlighting the usefulness. Control on the dispersion characteristics of such fibers may be imposed by making the guide even more complex; the possibility of devising such options is also touched upon.

The intensity of Raman scattering can be enhanced by a factor of 10⁶ using Surface Enhanced Raman Spectroscopy (SERS). In this method, molecules are placed within a few nm of a rough/nanostructured metal surface. In this paper we show fabrication and characterisation of an integrated optical waveguide beneath a nano-structured precious metal coated surface. By using a waveguide core, the excitation field comes from underneath and enters the nanostructures at the base. This allows the emission to reach the discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. The nanostructured geometry projects the Plasmon field into free space, thus increasing the cross section of interaction between the analyte molecules and optical fields, thereby increasing device sensitivity. Thin films of silicon oxynitride were deposited using PECVD on to thermal oxide coated 4 inch wafers and annealed at various temperatures to obtain low loss layers suitable for the waveguide core material. Based on the results from our simulations, nanostructured features of various diameters/feature lengths and pitch were etched into the low loss silicon oxynitride layer. The sensor area was coated with a thin layer of gold (25nm) and a variety of optical measurements were completed for many of the processed test chips including broadband reflectrometry, normal incident Raman spectroscopy and waveguide Raman spectroscopy using a Raman probe above the sensor area. The results showed that detection of a Raman active molecule (Benzyl Mercaptan) was possible when excited from the underlying waveguide core with 10⁴ sensitivity.

The propagation of a surface plasmon-polariton (SPP) wave can be guided by the interface of a metal and a columnar thin film (CTF). Theory predicts that the angle of incidence on the prism/metal interface in the Turbadar–Kretschmann–Raether prism-coupled configuration required to excite the SPP wave shifts upon infiltration of the CTF by a fluid. Otherwise identical CTFs of different thicknesses were partnered with dense thin films of aluminum in optical experiments. Regardless of the angle between the morphologically significant plane of the CTF and the cross-sectional plane of the prism, the angle of incidence for exciting the SPP wave was found to shift to a higher value when the CTF was infiltrated by a fluid of refractive index in excess of unity. Experimental data indicated that the angle between the morphologically significant plane of the CTF and the cross-sectional plane of the prism should not exceed about 45°◦ for high sensitivity.

We have investigated feasibility of waveguide-mode sensors, which is sensitized by a nanocolumnar SiO₂ waveguide layer deposited by an oblique angle deposition technique. Because the effective refractive index of nanocolumns and fluid composites (n₁) depends on that of fluid (n₂), sensitivity of the waveguide-mode sensors is expected to be improved. In fact, the resonant angle of incidence of the waveguide-mode sensors, which have various combinations of layer thicknesses, changes significantly depending on the analytes of air (n₂ = 1.00), H₂O (n₂ = 1.33) and C₂H₅OH (n₂ = 1.36). The effective refractive indices of the waveguide layer immersed in these fluid are estimated at 1.28 for air, 1.41 for H₂O and 1.42 for C₂H₅OH. The effective refractive index of the waveguide layer is understood by Bruggeman’s effective medium model. Therefore, the nanocolumnar waveguide layer is quite useful to improve sensitivity of the waveguide-mode sensors. In order to improve sensing sensitivity, more porous layer is desirable.

We have developed a new type of thin film composite material comprised of Mo:Al₂O₃ consisting of conducting metal nanoclusters embedded in an insulating Al₂O₃ matrix. These nanocomposite thin films were prepared by atomic layer deposition (ALD). Quartz crystal microbalance (QCM) experiments performed with various Mo cycle percentages revealed that the Mo ALD inhibits the Al₂O₃ ALD and vice versa. Despite this inhibition, the relationship between Mo content in the films and cycle percentage was close to expectations. Depth profiling X-ray photoelectron spectroscopy (XPS) showed that the Mo:Al₂O₃ films were uniform in composition and contained Al, O, and metallic Mo as expected, but also included significant F and C. Cross sectional TEM revealed the composite film structure to be metallic nanoparticles (2-3nm) embedded uniformly in an amorphous Al₂O₃ insulating matrix. The resistivity of these composite films could be tailored in the range of 10⁴ -10¹² Ohm-cm by adjusting the Mo ALD cycle percentage. These nanocomposite films have been used as resistive coatings in microchannel plate (MCP) fabrication and as charge-drain coatings in micro-electron-optical devices. Here we report the ALD growth characterization, and application of these of Mo:Al₂O₃, films.

Considering luminescent TiO₂ films whose surface was imprinted with a 2D square shaped photonic crystal with different pattern depths (from 20 to 61 nm), we demonstrate the possibility to use simple absorption measurements to evaluate the efficiency of light extraction. Absorption spectra of the patterned systems show absorption peaks, evidencing the coupling between the photonic crystal structure and light guided within the film, in good agreement with 2D-RCWA simulations. The deeper the pattern depth, the stronger the coupling between the guided light and the photonic crystal. Using RCWA simulations, we show that it is possible to evaluate the extraction length, characteristic of the efficiency of light extraction, from the absorption spectra, in good agreement with direct measurements reported elsewhere.

The efficiency of thin film solar cells can be improved by various known and extensively studied light trapping techniques such as textured interfaces, nano-particles, and so on. But all these methods are not expected to improve the efficiency of the solar cells with by same amount. In this paper, textured interfaces and nano-particles are simulated and their respective effect on the absorption of the active layer, aSi : H in this case, is observed. The nano-particles are silver nano-particles and for the interface simulations, different AFM scans are used. For the nano-particles simulations different position in the layer stack is simulated. To achieve this, Maxwell's equations are solved with Finite Difference Method(FDM) and Finite Integration Technique(FIT) and special scheme that accounts for the negative permittivity of silver. To accurately simulate the silver nano-particles the simulation is done with a fine discretization and run on high performance machines with a highly parallel iterative scheme.

Roughness structures are essential for a variety of functional surfaces, for example surfaces with extreme wetting behavior like superhydrophobicity or superhydrophilicity. On the other hand, roughness also gives rise to light scattering, and thus limits the usability of such surfaces for optical applications. Our approach is based on using small-scale intrinsic roughness components of thin film coatings to achieve the desired functional properties while keeping the light scattering at acceptable levels. A comprehensive measurement and analysis methodology for effectively predicting, defining and controlling the structural and wetting properties of stochastically rough superhydrophobic surfaces is presented. Power Spectral Density (PSD) functions determined from atomic force microscopy data are used for thorough roughness analysis as well as to predict the wetting and light scattering properties. Dynamic contact angle analysis is performed by measuring advancing, receding, roll-off, and bounce-off angles. Examples of natural and technical superhydrophobic surfaces like the Lotus leaf and thin film coatings with stochastic nanoroughness are given. These surfaces reveal high advancing contact angles, low contact angle hysteresis, low roll-off angles, and, consequently, the effect of self-cleaning.

The equivalent electromagnetic parameters of a three-layered system Air/ Ta₂O₅ NRA (165nm)/ SiO₂ NRA (133nm)/ Ag NRA(130nm) /BK7, fabricated by glancing angle deposition, are derived. The equivalent optical constants are used to estimate the optical performance that is achieved when additional films are deposited upon the NRA. First, the Ag NRA is deposited at a deposition angle of 89deg. An SiO₂ NRA is then deposited at a deposition angle of -89deg. Finally a Ta₂O₅ NRA is deposited upon the SiO₂ NRA at a deposition angle of 80deg. The reflectance and transmittance of the three-layered system Air/ Ta₂O₅ NRA (165nm)/ SiO₂ NRA (133nm)/ Ag NRA(130nm) /BK7 glass are measured and compared with the theoretically estimated reflectance. At a wavelength of 568nm, the theoretically estimated p-polarization reflectance is 21.75%, which is close to the measured reflectance of 20.3%. A suitable arrangement of dielectric thin films upon a metamaterial thin film is demonstrated to induce p-polarized transmission.

α-sexithiophene was deposited on KCl (100) by hot wall epitaxy technique at different substrate temperatures (60 °C 135 °C). The morphological investigation was performed by AFM and optical microscopy, revealing terraced islands and needle-like anisotropic structures. Structural investigations were performed by specular XRD scans. Upright standing molecules have been detected, which could be related to the terraced islands ((100) crystal contact plane). Furthermore, (010) and (-411) crystal planes have been observed, which explains the observed nano-needles (flat lying molecules). The texture was investigated by XRD pole figures, showing that all three crystal types exhibit a well defined azimuthal alignment with respect to KCl high symmetry directions. Interestingly, the epitaxial orientation of the islands could be explained by ledge directed epitaxy, which describes the nucleation of crystallites on existing topographic features on the substrate (nano-needles). A real space model of the crystallites was developed with the help of XRD pole figures and single crystal data. Surprisingly, the azimuthal orientation of the long moleculear axis is exactly the same for needles with (010) and (-411) contact planes. This observation represents a hint that the adsorption geometry of single molecules seems to be decisive for the organic crystal nucleation. Additionally, the substrate surface symmetry is nicely reflected by the multiplicity of formed needle orientations.

Traditional optical thin films exhibit low absorption when light is incident obliquely because the optical path decreases with increasing angle of incidence [1]. A thin film absorber is also a challenge to perform high absorption at oblique incidence. Under the condition of total reflection, a thin metal film with thickness around 40nm in a Kretschmann configuration (prism / metal film / air) enables to absorb light at an extremely small angle range by exciting surface plasmon at the interface of metal/air [2]. In this work, a metamaterial thin film composed of aluminum nanorods is fabricated and used to absorb light in high efficiency. An aluminum nanorod array (Al NRA) deposited obliquely is arranged in a prism-coupling system to observed the reflection under the condition of total reflection of the system: BK7 prism/ Al NRA/ Air. The Al NRA is 184nm thick and tilted at an angle of 35° with respect to the surface normal. The deposition plane defined by the directions of rod and surface normal is orientated at angles of φ=0° and φ=180° with respect to the plane of incidence to measure the reflectance versus incident angles from 45° to 70° and wavelengths from 400nm to 700nm. The definition of the NRAs orientation is shown in Fig. 3. When the deposition plane is the same with the plane of incidence, the reflectance spectra indicate that the Al NRA exhibits strong absorptance over 80% at angles of incidence from 45° to 55° for both p-polarization and s-polarization. The enhanced p-polarized absorptance is extended from 45° to 70°. At φ=90°, the absorptance is weaker at angles of incidence from 55° to 70° compared with other two cases measured at φ=0° and φ=180°°.

The spectral control of thermal radiation is demonstrated using an array of sprit-ring resonators as plasmonic metasurface. Thermally excited plasmonic resonant modes in a meta-atom are found to enhance thermal radiation at specific wavelengths. From numerical simulations, the emissivity at the resonance can be tuned to blackbody level by tuning the coupling between a sprit-ring and a metal substrate. Since the thickness of the metasurface is significantly small compared to the wavelength, these devices are promising candidates for extremely thin film thermal emitters or efficient frequency-converters for wide range of the frequency from infrared to visible.

The fabrication by nanoimprint lithography of large-area plasmonic and photonic sensing platforms is reported. The plasmonic nanostructures have the shape of split–ring resonators and support both electric dipole and quadrupole modes. They carry the spectral signature of Fano resonances. Their near-field and far-field optical properties are investigated with an analytical model together with numerical calculations. Fano-resonant systems combine strong nanoscale light confinement with a narrow spectral line width, which makes them very promising for biochemical sensing and immunoassays. On the other hand, chemical sensors based on resonant gratings are obtained by patterning a sol-gel material, evaporating a high refractive index semiconductor and coating with a chemically sensitive dye layer. By exposition to a liquid or an invisible gas such as ammonium, the change in absorption is detected optically. An analytical model is introduced to explain the enhancement of the signal by the resonant grating, which can be detected with the naked eye from a color change of the reflected light.

Surface Enhanced Raman Spectroscopy (SERS) allows the intensity of Raman scattering to be enhanced by a factor of 10⁶ by placing molecules within a few nm of a rough metal surface. In this paper we continue our investigation into a completely different configuration for a SERS sensor platform, incorporating an optical waveguide beneath a nanostructured precious metal coated surface. The nanostructured geometry projects the Plasmon field into free space, thus increasing the cross section of interaction between the analyte molecules and optical fields, thereby increasing device sensitivity. In this arrangement the excitation field comes from underneath and enters the nanostructures at the base. This allows the emission to reach the discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. Using Finite Difference Time Domain (FDTD) modelling methods the waveguide coupled SERS nanostructures were fully analyzed and their theoretical performance simulated by using frequency domain power monitors around the nanostructures. The model investigates efficiency of coupling between the waveguide and surface plasmons, but also investigates spatial localization around sharp features of the geometry. Simulations were completed using different types of etched nanostructures (pyramidal, circular, square) and dimensions to determine a suitable sensor area which would allow for maximum field intensity within the features when excited from underneath. The simulations suggested that a pitch of 2500nm, a circular feature length of 500nm and an etch depth of 400nm showed more field intensity within the nanostructured pits.

Propyl ammonium bromide C3, carbazole-linked and naphtalen-linked ammonium bromides CBz and Nap, and PbBr₂ Pb were dissolved in dimethylformamide (DMF) at the molar ratio of C3:CBz:Pb and C3:Nap:Pb = 2:0:1, 4:2:3, 1:1:1, 2:4:3, and 0:2:1. The thin films were prepared on fused quartz substrates by spin-coating from the DMF solutions. Super layer structure, where organic dielectric layer, inorganic semiconductor layer, and organic semiconductor are assembled in order, was successfully constructed by a simple spin-coating with the solution in which propyl ammonium bromide C3, carbazole-linked propyl ammonium bromide CBz, naphthalene-linked ammonium bromides Nap and PbBr₂ Pb (the molar ratio;C3 : CBz : Pb and C3 : Nap : Pb= 4 : 2: 3) were dissolved .

n-Type transparent conducting indiuim galium zinc oxide (IGZO) films were successfully grown on glass sub- strates at room temperature by rf magnetron sputtering . Structural, optical, morphological and electrical properties of IGZO films deposited at different rf power were investigated.Composition of the film was confirmed by EDAX measurement which shows that percentage of Zn increased with the rf power. Structural studies by X-ray diffraction showed that as deposited IGZO films were amorphous. The roughness of the film was increased with increase in rf power and smooth film of average roughness 0.75nm was obtained at 40W rf power. The average transmission in the visible range was greater than 80% and the transmission in the higher wavelength re- gion decreased with increase in RF power. Refractive index of IGZO film calculated by Swanepoel technique was 1.92. The carrier concentration in IGZO films can be controlled by controlling rf which can vary Zn/(Ga+In+Zn) ratio. The bottom gate structured transparent TFTs fabricated using n-type IGZO active layers operated in enhancement mode with field effect mobility 2.5 cm²/Vs and threshold voltage 20V.

This study presents a GaN thin film light-emitting diode (TF-LED) on an electroplated flexible copper substrate to improve thermal conduction effect of the LED. The optoelectronic characteristics and stress effect of the GaN TF-LEDs on the electroplated flexible copper prepared by laser lift-off technique was examined. The surface of the peeled GaN TF-LED after laser lift-off process demonstrated a pore array. The GaN pore array surface was etched by photo-electrochemical method to form hexagonal pyramid hillocks on the surface using KOH solution. Then, freestanding peeled GaN TF-LEDs with the front surface protected by wax were immersed into 3M KOH solution at 10, 20, 30min under ultraviolet illuminations to perform the photo-electrochemical etching. Surface morphologies with and without photo-electrochemical etching were observed by field emission scanning electron microscope (FESEM) (LEO 1530).

To construct a solar cell with maximal efficiency it is necessary to minimise the remittances of the cell across the solar spectrum. Thin-film solar cells allow for production of solar cells with reduced cost, weight and rare mineral consumption; furthermore, engineering at the nanoscale may achieve the high levels of solar absorption attainable with traditional, thicker cells. Columnar thin films (CTFs) have the potential to fulfil these requirements, as by infiltrating the voids between the column with a fluid and by tailoring the shape of the columns, the optical properties can be tuned. Here we present a mathematical framework for calculating the absorptance of such an infiltrated CTF. Also presented are some preliminary numerical results, based on a titanium oxide CTF. These simulations imply that by decreasing the columnar angle (the angle between the column and the substrate) much higher levels of absorption can be achieved, as compared to a CTF with columns oriented normal to the substrate.

In this work, three different aluminum (Al) / silicon-dioxide (SiO₂) / aluminum (Al) nanosandwich films (SWFs) with different sizes are deposited using glancing angle deposition (GLAD) with continuous azimuthal rotation. The SWF comprises an SiO₂ layer that is sandwiched between Al nanopillars. The thickness of SiO₂ is fixed at 45nm. The thicknesses d of the top and bottom Al nanopillar is varied from 188nm to 233nm. The equivalent electromagnetic parameters of each film are derived from the reflection coefficients and transmission coefficients that are measured by walk-off and polarization interferometers. The equivalent optical parameters revealed that it has a negative real equivalent permittivity and a negative real equivalent permeability. The effect of size of the Al / SiO₂ / Al SWFs on their optical properties is also examined. As the thickness d increases from 188nm to 233nm, the equivalent refractive index is negative and its average magnitude decreases from -1.703 to -1.247. Similarly, the real part of the equivalent permittivity varies from -1.193 to -0.824 as the thickness increased. The SWFs are simulated to analyze the magnetic field in the SiO2 layer by finite-difference time-domain (FDTD) method. The result of the simulation shows that the negative permeability arises from the reversal of the magnetic resonance within the SiO2 layer. The reversed magnetic field becomes weaker as the thickness d increases.