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Organic solar cells (OSCs) are a complex assembly of disparate materials, each with a precise function within the device. Typically, the electrodes are flat, and the device is fabricated through a layering approach of the interfacial layers and photoactive materials. This work explores the integration of high surface area transparent electrodes to investigate the possible role(s) a three-dimensional electrode could take within an OSC, with a BHJ composed of a donor–acceptor combination with a high degree of electron and hole mobility mismatch. Nanotree indium tin oxide (ITO) electrodes were prepared via glancing angle deposition, structures that were previously demonstrated to be single-crystalline. A thin layer of zinc oxide was deposited on the ITO nanotrees via atomic layer deposition, followed by a self-assembled monolayer of C60-based molecules that was bound to the zinc oxide surface through a carboxylic acid group. Infiltration of these functionalized ITO nanotrees with the photoactive layer, the bulk heterojunction comprising PC71BM and a high hole mobility low band gap polymer (PDPPTT-T-TT), led to families of devices that were analyzed for the effect of nanotree height. When the height was varied from 0 to 50, 75, 100, and 120 nm, statistically significant differences in device performance were noted with the maximum device efficiencies observed with a nanotree height of 75 nm. From analysis of these results, it was found that the intrinsic mobility mismatch between the donor and acceptor phases could be compensated for when the electron collection length was reduced relative to the hole collection length, resulting in more balanced charge extraction and reduced recombination, leading to improved efficiencies. However, as the ITO nanotrees increased in height and branching, the decrease in electron collection length was offset by an increase in hole collection length and potential deleterious electric field redistribution effects, resulting in decreased efficiency.

RATIONALE Thin, nanoporous films fabricated using Glancing Angle Deposition (GLAD) technology are demonstrated for solid matrix laser desorption/ionization mass spectrometry (SMALDI-MS). GLAD allows facile engineering of nanoporosity, film thickness, post alignment, and material composition, as demonstrated here by the fabrication of Co-GLAD and Si-GLAD films for SMALDI, and by exploration of the SMALDI performance as a function of thickness, post density, and angle of the post relative to surface normal. METHODS GLAD films were prepared by electron beam evaporation onto silicon substrates, using steep angles of incidence for the vacuum deposition, with computer controlled substrate rotation. LDI from the GLAD films was evaluated using an MDS-Sciex time-of-flight (TOF) MALDI mass spectrometer. RESULTS Co-GLAD films give a limit of quantitation of 6 fmol for complex carbohydrate derivatives, and slanted-post Si-GLAD films show up to three times higher sensitivity than vertical post structures. Reproducibility of both Si and Co films is much higher than conventional MALDI methods for m/z below at least 2100 Da. Both reproducibility and detection limits are comparable to or better than other nano-structured materials. Co-GLAD films are significantly better in performance than Co powders or Co thin films on silicon substrates previously evaluated. CONCLUSIONS The flexibility of GLAD for thin film fabrication of LDI materials is demonstrated by the range of nanoporous materials that can be grown, and the fine control over structural conformation, thickness and porosity. Copyright © 2017 John Wiley & Sons, Ltd.

A series of Ni1–xFex hydrous oxide nanoparticles (HO-nps, x = 0–0.5, 1) were prepared by stirring 0.1 M KOH solutions of NiCl2 and FeCl2 under air at room temperature. The resulting HO-nps can be used directly, or washed and isolated without loss of activity. The Ni1–xFex HO-nps are outstandingly active and stable toward the water oxidation reaction (WOR) in base. The Ni0.75Fe0.25 HO-np was the most active mass-normalized WOR catalyst in the series, with onset overpotential = 190 mV, Tafel slope = 24 mV dec–1, overpotential at 10 mA cm–2 = 234 mV, and loadings Ni + Fe = 0.135 mg cm–2. The catalysts were robust under long-term galvanostatic and duty-cycle testing. The Ni0.75Fe0.25 HO-np catalyst has a layered double hydroxide structure, and it appears that Fe enhances the activity of Ni toward the WOR by decreasing its electron density.

Ir–Ni oxide nanoparticles were simply prepared by stirring IrCl3 and NiCl2 precursors in aqueous base under air. The activities of a series of IrNiyOx nanoparticles with different Ir-to-Ni ratios were measured toward water oxidation in 0.1 M H2SO4. The Ir-to-Ni ratio was 1:0.125 in the most active catalyst (mass normalized > 140 A g−1 Ir, electrochemically active surface area normalized > 203 A mmol−1Ir). The stabilized potential for the galvanostatic oxidation (1 mA cm−2geometric) was as low as 1.51 VRHE, corresponding to 0.28 V in overpotential. Keywords: Water oxidation, Oxygen evolution, Iridium, Nickel, Water electrolyzer

Exploitation of anodically formed self-organized TiO2 nanotube arrays in mass-manufactured, disposable biosensors, rollable electrochromic displays and flexible large-area solar cells would greatly benefit from integration with transparent and flexible polymeric substrates. Such integration requires the vacuum deposition of a thin film of titanium on the desired substrate, which is then anodized in suitable media to generate TiO2 nanotube arrays. However the challenges associated with control of Ti film morphology, nanotube array synthesis conditions, and film adhesion and transparency, have necessitated the use of substrate heating during deposition to temperatures of at least 300 degrees C and as high as 500 degrees C to generate highly ordered open-pore nanotube arrays, thus preventing the use of polymeric substrates. We report on a film growth technique that exploits atomic peening to achieve high quality transparent TiO2 nanotube arrays with lengths up to 5.1 microm at room temperature on polyimide substrates without the need for substrate heating or substrate biasing or a Kauffman ion source. The superior optical quality and uniformity of the nanotube arrays was evidenced by the high specular reflectivity and the smooth pattern of periodic interferometric fringes in the transmission spectra of the nanotube arrays, from which the wavelength-dependent effective refractive index was extracted for the air-TiO2 composite medium. A fluorescent immunoassay biosensor constructed using 5.1 microm-long transparent titania nanotube arrays (TTNAs) grown on Kapton substrates detected human cardiac troponin I at a concentration of 0.1 microg ml(-1).

Single-crystal indium tin oxide (ITO) nanotrees with engineered trunk and branch orientations are grown using a recently reported technique combining vapor-liquid-solid growth and glancing angle deposition (VLS-GLAD). In this work, three unique capabilities of VLS-GLAD are demonstrated for the first time: (i) nanotrees are aligned without epitaxy, (ii) branches can be placed on select faces of the nanotree trunk, and (iii) branch orientation can be modified along the height of nanotrees. VLS-GLAD uses a collimated obliquely incident vapor flux to place material on desired growth surfaces, resulting in preferential branch growth on the sides of the nanotree trunk exposed to the flux at the time of nucleation. Dynamic control of the azimuthal orientation of the flux relative to a growing nanotree enables the preferential orientation of branches to be modulated along the height of the nanotree, which we have demonstrated with both continuous and discrete substrate rotation schemes. An electron diffraction investigation confirms that the nanotrees can be considered as a single crystal, with continuity of the crystal structure across the trunk-branch interface. Crystal texture of the films is characterized by X-ray diffraction pole figures. By limiting the flux to discrete positions, the films develop both out-of-plane and in-plane crystal alignment (biaxial texture). We interpret the in-plane orientation as the result of competitive growth, which leads to evolutionary selection of similarly oriented structures. Control over in-plane nanotree crystal alignment and height-dependent branch orientation should increase the achievable complexity in three-dimensional nanowire architectures. © 2012 American Chemical Society.

Nb-doped TiO2 (TNO) has been widely explored as an alternative transparent conductor. TNO thin films have been fabricated by various deposition methods, and here we demonstrate fabrication by evaporation of sol–gel synthesized TNO source material. A range of NbxTi1 − xO2 (x = 0, 0.03, 0.06, 0.12, 0.24) compositions were synthesized, pressed into pellets, and deposited as thin films via electron beam evaporation. The thin films were characterized for composition by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy and for crystallinity by X-ray diffraction for the different Nb contents explored. Transparency, conductivity, and Haacke transparent conductor figure of merit values are reported for the evaporated TNO films as a function of Nb content, substrate heating temperature, and post deposition annealing conditions. Glancing angle deposition (GLAD) is used to demonstrate nanostructuring of evaporated TNO based on physical shadowing. Nanostructured GLAD TNO films of increased morphological complexity can be produced using this method, and could lead to unique transparent conductor device architectures.

Metal oxides such as niobium oxides have been demonstrated as alternative support materials for Pt and non-precious metal catalysts in fuel cells. High surface area and columnar niobium oxide catalyst support structures were produced by the glancing angle deposition (GLAD) technique on 5 mm diameter glassy carbon disks. The columnar structures have lengths of about 500 nm, diameters of 50 nm and an areal density of about 10 9 cm −2 . Annealing under different gas mixtures (Ar/H 2 ) led to the formation of various oxides (Nb 2 O 5 , NbO 2 , or NbO + NbO 2 ). Pt catalyst, with a loading of 0.1 mg Pt cm −2 , was deposited onto these structures by magnetron sputter deposition. Rotating disk electrode characterization of the samples, performed in 0.1M HClO 4 electrolyte at room temperature, revealed surface enhancement factors of up to 11 and oxygen reduction specific activities of ≥1 mA cm −2 Pt at 0.9 V (vs. RHE). The impact of annealing on Nb-O phase formation, conductivity, oxygen reduction activity and stability are discussed.

We tailored nanostructured morphology and crystal texture of iron nanocolumns by engineering the inclination and azimuthal directions of the collimated flux characteristic of glancing angle deposition (GLAD). Under continuous substrate rotation, the flux is azimuthally isotropic within one rotation. With large substrate rotation speeds, we can deposit vertical nanocolumns with a faceted, tetrahedral apex, BCC crystal structure and 111 fiber texture. Designing the flux to have an azimuthal 3-fold symmetry, which reflects the symmetry of the tetrahedral apex, allows us to induce both an in-plane and out-of-plane texture (biaxial texture) by evolutionary selection. In-plane crystal orientation is accompanied by a preferential azimuthal nanocolumn orientation, where the sides of tetrahedral apex are directed toward the flux direction. This work demonstrates the flux engineering technique, which can orient in-plane crystal texture and morphology of crystalline nanocolumns on amorphous substrates. This control is a useful addition to vapor–solid, physical self-assembly with the potential to improve the performance of porous thin film architectures as biaxial buffer layers, and in a variety of device applications such as photovoltaics and energy storage.

Fabrication of interdigitated organic photovoltaic (OPV) devices commonly involves filling a nanostructured thin film using solution-based methods. In these cases, the sensitivity of the nanostructured films to the solvents used needs to be studied in order to optimize the interface. Here, we study the ability of chlorobenzene (CB) and dichlorobenzene (DCB) to dissolve and recrystallize zinc phthalocyanine (ZnPc) thin films, while fabricating interdigitated active layers composed of ZnPc and [6,6]-phenyl-C 61 butyric acid methyl ester (PCBM). Using glancing angle deposition (GLAD), we are able to construct slanted nanorod arrays of ZnPc, with nanorod diameters of nominally 40 nm and lengths up to 450 nm. We find that these films are recrystallized upon direct exposure to CB and DCB, regardless of initial morphology, yielding a variety of possible nanoscale formations. The crystallinity and absorbance of these recrystallized films changes as well, depending on solvent choice and exposure time. Through control of initial ZnPc film morphology and solvent choice for PCBM casting, we exploit the sensitivity of ZnPc to these organic solvents to optimize the photovoltaic performance of ZnPc/PCBM devices. Optimal OPV device performance is achieved with a 30 nm thick GLAD-textured ZnPc film while using DCB as the PCBM solvent. In this case, power conversion efficiencies are up to 3.0%, compared to an average of 2.3% when using CB as the solvent on the same film, and 2.3% also for bilayer devices when using DCB as the solvent. A higher degree of material mixing at the ZnPc/PCBM interface is shown when using DCB over CB as the PCBM solvent, which may be the primary mechanism for the photovoltaic improvements seen in these devices. © 2011 Elsevier B.V. All rights reserved.

Ultrathin-layer chromatography (UTLC) provides the high sensitivities and rapid separations over short distances desirable in many analytical applications. The dependence of these performance benefits on UTLC layer microstructure motivates continued stationary phase engineering efforts. A new method of modifying the elution behaviours of nanostructured thin film UTLC stationary phases is investigated in this report. Macroporous normal phase silica thin films ~5μm thick were fabricated using glancing angle deposition (GLAD). Reactive ion etching (RIE) and a subsequent annealing treatment modified stationary phase morphology to tune migration velocity, analyte retention, and overall separation performance. Combining this technique with a RIE shadow mask enabled fabrication of adjacent concentration and separation zones with markedly different elution properties. Although produced using an entirely new approach, GLAD UTLC concentration zone media behaved in a manner consistent with traditional thin-layer chromatography (TLC) and high-performance TLC (HPTLC) concentration zone plates. In particular, these new media focused large volume, low concentration dye mixture spots into narrow bands to achieve high-quality separations. The described approach to modifying the morphology and resultant elution behaviours of nanostructured stationary phases expands the capabilities of the GLAD UTLC technique. © 2011 Elsevier B.V.

The structural color of mesoporous photo­nic crystals (PCs) is highly sensitive to environmental changes, making them ideally suited as optical sensors. Here, this effect is exploited in the nanofabrication and characterization of an optimized PC design for humidity sensing. The sensor performance is excellent and the new quantitative analysis methods developed will be useful for future color‐based sensor design.

The porous nature of high surface area and large aspect ratio nanorods arrays make them strong candidates for a range of applications from catalyst supports to energy scavenging devices. The glancing angle deposition (GLAD) technique is a straightforward and flexible method for ensuring control of morphology and porosity in nanorod arrays. Quantifying the porous nature of nanostructured columnar arrays, fabricated using the GLAD technique, is critical for understanding and optimizing the performance of devices fabricated using this method. The mesoporosity and pore volume of these GLAD nanorod arrays have thus been characterized using gas adsorption (krypton adsorption at 87.3 K) and scanning electron microscopy (SEM) image analysis techniques. To characterize the obliquely deposited amorphous titanium dioxide (TiO 2 ) and silicon dioxide (SiO 2 ) samples, top-down SEM images of the films were also analyzed which allowed us to determine the mean distance between columns. SEM image analysis permitted for estimation of inter-column porosity of films deposited at angles from 65° to 85°, while krypton analysis allowed for the identification of mesoporosity in films from 45° to 85°. Our results provide a comprehensive characterization of GLAD film porosity which will be vital for the design of devices for a diverse set of applications from photonics to sensing to microfluidics.

Relative humidity sensors with a nanostructured titanium dioxide sensing layer were fabricated using glancing angle deposition. Such sensors exhibit very quick response times and high sensitivity but are prone to aging. In previous work, ultraviolet irradiation has been shown to regenerate and improve the sensor performance. Here, the effect of ultraviolet wavelength and power on sensor performance, aging, and regeneration was studied. In order to quantify the change in sensor response a figure of merit (FOM) was defined as the integrated area between the sensor response curves before and after regeneration or aging. FOM values ranged from 2.1 to 61 for treatment with a mercury vapor lamp. Treated sensors aged at an average rate of -0.43 FOM/day. Regeneration of sensors using commercial ultraviolet light-emitting diodes was demonstrated, resulting in FOMs significantly larger than irradiation with comparable mercury vapor lamp wavelengths.

Nanopillar metal oxide thin films offer versatility as ultra high surface area supports and conductors. Metal oxide properties (e.g. stability, conductivity) can be tuned via phase and composition control to achieve desired application-specific functionality. Here we demonstrate phase control of high surface area thin films grown by glancing angle deposition and transformed to desired phases through high temperature annealing in a reducing environment. The post-annealed properties such as stoichiometry, phase, and morphology are shown to be largely dependent on initial film structure and hydrogen forming gas flow rate. Initially amorphous films of approximate stoichiometry Nb 2 O 5 are transformed to NbO 2 or NbN x O 1− x through annealing. Transformation to oxygen-deficient phases is more easily achieved for films of higher initial porosity. Higher forming gas flow rates result in both increased oxygen removal and significantly less physical degradation of nanostructures. A phase map is included as a guide to phase formation and morphology control in annealed nanopillar niobium oxide films.

We investigate the performance of highly anisotropic nanostructured thin film ultrathin-layer chromatography (UTLC) media with porosity and architecture engineered using the glancing-angle deposition (GLAD) process. Our anisotropic structures resemble nanoblades, producing channel-like features that partially decouple analyte migration from development direction, offering new separation behaviours. Here we study GLAD-UTLC plate performance in terms of migration distance, plate number, retention factor and a figure of merit specific to GLAD-UTLC, track deviation angle. Migration distances increase with porosity by a factor of two for all feature orientations (up to a maximum of 22. mm) over the range of porosities considered in this study. Plate numbers approaching 1100 are observed for GLAD-UTLC plates when the nanoblade features are aligned with the development direction. We present a theoretical model describing mobile phase flow in anisotropic GLAD-UTLC media, and find good agreement with experimental results. Our plates provide channel features that reduce transverse spot broadening while providing the wide pores required for rapid migration and high separation performance. These improvements may enable a greater number of parallel separations on miniaturized GLAD-UTLC plate formats. Their small sizes should also make them compatible with the Office Chromatography concept in which office peripherals (inkjet printers and flatbed scanners) replace conventional TLC instruments. Equipped with a better understanding of the unique GLAD-UTLC elution behaviours, we expect to further improve performance in the future. © 2010 Elsevier B.V.

We report on the optimization of nanostructured copper phthalocyanine (CuPc) thin films for idealized organic photovoltaic (OPV) architectures using advanced substrate motion and periodic seeding. Oblique angle deposition (OAD), a subset of glancing angle deposition (GLAD), has recently been used to enhance small molecule OPV device photoconversion efficiency by increasing the surface area of metal phthalocyanine (MPc) thin films. Here we report a detailed study of how to direct MPc film growth towards the ideal donor morphology using the techniques available to GLAD. Porous films of columnar CuPc nanostructures were achieved with strong control over the diameter, spacing and height of the columns. Special emphasis was placed on limiting column broadening as the film thickness, and resulting light absorption, was increased. Columns were grown on PEDOT:PSS coated ITO substrates to hundreds of nanometers in length while maintaining diameters of 40-50 nm and crystal grain sizes of 15-30 nm. Additionally, we provide the first demonstration of periodically seeded organic nanocolumn growth. These methods enable fabrication of uniform columnar MPc films engineered specifically for the short exciton diffusion lengths in these materials, making them suitable for ideal OPV device geometries. © 2011 The Royal Society of Chemistry.

Porous structured films grown with the glancing angle deposition technique have been widely studied for thin film optical device applications. We report the use of ion assistance to modify the structural and optical properties of porous silicon dioxide and titanium dioxide columnar thin films grown at deposition angles of 70° and 85°. Optical characterization studies show that tilted columnar structures will undergo an increase in tilt angle and film density with increasing ion dose. These two trends contrast with unassisted films where film density and column tilt angle are primarily controlled by the deposition angle. Thus, a regime of film structures simultaneously exhibiting high film density and large column tilt angle is enabled by incorporating an ion-assisted process. The phisweep substrate motion algorithm for minimizing columnar anisotropy used in conjunction with ion-assisted deposition provides additional control over film morphology and expands the utility of this modified fabrication process.

Glancing angle deposition (GLAD) was used to deposit controlled-porosity TiO 2 thin films of varying pore size and shape. Hybrid materials were fabricated by infiltrating the TiO 2 films with poly(3-hexylthiophene) (P3HT) using a spin casting process, which were either employed as-cast or subjected to thermal processing. Photovoltaic devices fabricated using these hybrid materials were characterized as a function of TiO 2 pore size and shape, and thermal processing. It was found that the optimum pore size was dependent on the thermal history of the sample. When as-cast hybrid materials were employed conversion efficiencies decreased with increasing pore size. When hybrid materials annealed above the melting point of P3HT were employed the trend was reversed, with conversion efficiency increasing with increasing pore size. Trends in conversion efficiency were found to correlate with P3HT crystallinity, demonstrating that optimum pore sizes for hybrid devices of this type are dependent on sample processing.

Glancing angle deposition (GLAD) was used to fabricate nanostructured silicon (Si) thin films with highly controlled morphology for use in laser desorption/ionization mass spectrometry (DIOS-MS). Peptides, drugs and metabolites in the mass range of 150–2500 Da were readily analyzed. The best performance was obtained with 500 nm thick films deposited at a deposition angle of 85°. Low background mass spectra and attomole detection limits were observed with DIOS-MS for various peptides. Films used after three months of dry storage in ambient conditions produced mass spectra with negligible low-mass noise following a 15 min UV-ozone treatment. The performance of the Si GLAD films was as good as or better than that reported for electrochemically etched porous silicon and related materials, and was superior to matrix-assisted laser desorption/ionization (MALDI)-MS for analysis of mixtures of small molecules between 150–2500 Da in terms of background chemical noise, detection limits and spot-to-spot reproducibility. The spot-to-spot reproducibility of signal intensities (100 shots/spectrum) from 21 different Si GLAD film targets was ±13% relative standard deviation (RSD). The single shot-to-shot reproducibility of signals on a single target was ±19% RSD (n = 7), with no indication of sweet spots or mute spots. Copyright © 2010 John Wiley & Sons, Ltd.

A cationic and water-soluble polythiophene [poly[3-(6-pyridiniumylhexyl) thiophene bromide] (P3PHT + Br - )] is synthesized and used in combination with anionic poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) (PEDOT:PSS) - to produce hybrid coatings on indium tin oxide (ITO). Two coating strategies are established: i) electrostatic layer-by-layer assembly with colloidal suspensions of (PEDOT:PSS) - , and ii) modification of an electrochemically prepared (PEDOT:PSS) - film on ITO. The coatings are found to modify the work function ofITO such that it could act as a cathode in inverted 2,5-diyl-poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) polymer photovoltaic cells. The interfacial modifier created from the layer-by-layer assembly route is used to produce efficient inverted organic photovoltaic devices (power conversion efficiency ~2%) with significant long-term stability in excess of 500 h.

The strong dependence of separation behavior on ultrathin-layer chromatography (UTLC) stationary phase microstructure motivates continued UTLC plate design optimization efforts. We fabricated 4.6-5.3 mum thick normal phase silica UTLC stationary phases with several types of in-plane macropore anisotropies using the glancing angle deposition (GLAD) approach to engineering nanostructured thin films. The separation behaviors of two new media, isotropic vertical posts and anisotropic bladelike films, were compared to that of anisotropic chevron media. Channel-like structures within the anisotropic media introduced preferential mobile phase flow directions that could be exploited to give separation tracks diagonal to the development direction. Extraction of chromatograms from these angled tracks required the development of a new analytical approach that involved a commercial flatbed film scanner and custom numerical image analysis software. GLAD stationary phase performance was quantified using the Dimethyl Yellow dye separated from a lipophilic dye mixture over migration distances less than approximately 10 mm. The limits of detection were 10 +/- 4 ng for the vertical posts and 11 +/- 3 ng for the bladelike media. We obtained theoretical plate heights that varied with film microstructure between 12 and 28 mum. Unoptimized separation performance was comparable to that of other planar chromatography media. Macropore anisotropies engineered by GLAD may expand the capabilities of future UTLC stationary phases.

The glancing angle deposition (GLAD) technique is used to fabricate nanostructured thin films with high surface area. Quantifying this property is important for optimizing GLAD-based device performance. Our group has used high-sensitivity krypton gas adsorption and the complementary technique of cyclic voltammetry to measure surface area as a function of deposition angle, thickness, and morphological characteristics for several metal oxide thin films. In this work, we studied amorphous titanium dioxide (TiO(2)), amorphous silicon dioxide (SiO(2)), and polycrystalline indium tin oxide (ITO) nanostructures with vertical and helical post morphologies over a range of oblique deposition angles from 0 to 86 degrees. Krypton gas sorption isotherms, evaluated using the Brunauer-Emmettt-Teller (BET) method, revealed maximum surface area enhancements of 880 +/- 110, 980 +/- 125, and 210 +/- 30 times the footprint area (equivalently 300 +/- 40, 570 +/- 70, and 50 +/- 6 m(2) g(-1)) for vertical posts TiO(2), SiO(2), and ITO. We also applied the cyclic voltammetry technique to these ITO films and observed the same overall trends as seen with the BET method. In addition, we applied the BET method to the measurement of helical films and found that the surface area trend was shifted with respect to that of vertical post films. This revealed the important influence of the substrate rotation rate and film morphology on surface properties. Finally, we showed that the surface area scales linearly with film thickness, with slopes of 730 +/- 35 to 235 +/- 10 m(2) m(-2) microm(-1) found for titania vertical post films deposited at angles from 70 to 85 degrees. This characterization effort will allow for the optimization of solar, photonic, and sensing devices fabricated from thin metal oxide films using GLAD.

We fabricate 2D–3D photonic crystal heterostructures based on the silicon [001]-diamond:1 square spiral geometry using glancing angle deposition. We compare the normal incidence reflection properties of the fabricated 2D–3D heterostructures to simulated spectra generated using finite-difference time-domain calculations. Reflection peaks are observed, resulting from the presence of a photonic band gap, and defect modes are created by the 2D layer. Deterioration of the reflectance peaks with increased number of vertical spiral periods is observed. A series of square spiral structures are fabricated with a varying number of vertical periods to quantify the degradation of reflection peaks. At normal light incidence, a maximum reflection peak is observed from the film with three vertical periods. Beyond three spiral rotations, deterioration of the substrate-plane periodicity causes scattering losses.

We have studied the optical properties of nanostructured TiO 2 films and demonstrated the ability to tune the refractive index of the material over a wide range. The nanostructured films are fabricated using glancing angle deposition, which provides the ability to precisely control the density of the deposited film. Film morphology was examined using scanning electron microscopy and the films were optically characterized by polarized-reflectance measurements. A simple isotropic homogeneous model, which is shown to be a good approximation of the film, is used to determine the optical constants from the reflectance measurements. Improvements to the model are suggested.

Two unique fluorene monomers (PTE and MTE) and polyfluorene-based homopolymers (PPTE and PMTE) containing covalently linked aromatic ether (AE) moieties were synthesized via microwave Ni(0)-mediated Yamamoto coupling reactions. The monomers and polymers demonstrated thermal stabilities, as determined by TGA, much higher than status quo poly(9,9′-dioctylfluorene) (PFO) (i.e., greater than 100 °C), and most importantly, the spectral emission remained stable after annealing in ambient and inert atmospheres. PPTE and PMTE were annealed in an N2 atmosphere at 200 °C for 72 h and at 150 °C in ambient atmosphere for 1 h showing no evidence of green emission, in stark contrast to PFO. The results show that PFs with AE moieties present in the 9-position exhibit stable blue emission.

In this paper, we introduce a simple single-step method for creating spatially graded helical nanostructured thin films. The films mimic some of the interesting polarization and coloration properties found in nature and enhance the application prospects for helically structured thin films. Our helical nanostructures, fabricated using a variant of the glancing angle deposition technique (GLAD), are spatially graded with thicknesses that vary by several microns across substrate lengths of several tens of centimeters. These thickness gradations are predicted by simulation and verified by scanning electron microscopy (SEM). The resultant films act as Bragg multilayers and can be employed as optical filters which not only preferentially transmit one handedness of circularly polarized light, but also allow for spatially determined frequency tunability. Through spectroscopic measurements, we demonstrate that when appropriate deposition conditions are chosen these nanostructures exhibit strong polarization selectivity, concurrent with excellent frequency tunability. The preferentially transmitted peak wavelength can be changed from approximately 620 to 690 nm by translating the film over a spatial distance of 30 mm. These graded nanostructures can be incorporated into photonic and sensing devices. The grilled helical nanostructures may also be useful for providing a graded scaffolding to support liquid crystals.

Columnar titanium structures were fabricated on smooth glassy carbon (GC) disks using the glancing angle deposition (GLAD) physical vapour deposition technique. This catalyst support consists of 500 nm long posts with a nominal cross-sectional diameter of 100 nm. They have a number density of about 10 billion per cm2 which increases the effective surface area of the GC disks by a factor of 13. Platinum films ranging from 10 to 90 nm in thickness (planar equivalent) were deposited onto these posts by magnetron sputtering. The oxygen reduction activity and H2O2 release of these electrocatalysts were measured by the rotating ring-disk electrode method in O2-saturated 0.1 M HClO4 at room temperature. The electrochemical surface area of the catalysts, obtained from Hupd cyclic voltammograms, is about 10–15 times higher than smooth Pt films. The supports can be fabricated from most vacuum-compatible materials and should be stable over a wide range of processing, annealing, and operating conditions.

Glancing angle deposition was used to fabricate TiO 2 thin film relative humidity sensors. These sensors have been shown to have an extremely high capacitive response along with sub-second response times. However, the thin film morphology that gives rise to the strong performance also renders the film vulnerable to ageing processes which can degrade sensor performance over a period of days. In this paper, the evolution of sensor response in time was studied. The response of our sensors to ultraviolet irradiation was investigated, and shown to not only reverse the ageing of our sensors, but also increase the overall device response.

We have developed a range of thin film coatings that are transparent in the visible, electrically conducting, adjustably birefringent and capable of aligning calamitic liquid crystals. The coatings were fabricated from indium tin oxide by oblique or glancing angle deposition, and a wide range of microstructures such as helices, chevrons, uniaxial posts and biaxial slabs were produced. Under many deposition conditions, these structures showed optical transmittance and electrical conductivity comparable to standard indium tin oxide, yet a strong form birefringence (Δn > 0.07 at 589 nm) was also measured. In addition, many coatings were found to be capable of aligning liquid crystals along a common director, leading us to conclude that the technology may be useful in liquid crystal displays and other lightwave applications.

Traditional liquid crystal alignment techniques influence mesogen alignment at the substrate alone, and rely on interactions between molecules to extend that alignment throughout a device's thickness. An alternative approach is the use of a nanostructured host that provides a large surface contact area with a guest liquid crystalline material and can extend for micrometres beyond the substrate. This permits a greater degree of control over the mesogens and allows alignment control throughout the thickness of the nanostructured host. We present the realization and experimental results using hosts fabricated through a specialized thin film process known as glancing angle deposition.

Thin films were fabricated by glancing angle deposition (GLAD), a technique providing accurate control of the nanoscale geometry in the film. We demonstrate the ability of GLAD to create structures with a sinusoidal refractive index variation in the direction normal to the film surface. The structural periodicity prevents the transmission of light over a wide optical spectrum, creating a photonic stopband. By changing the parameters of the GLAD technique, a set of titanium dioxide films have been created exhibiting stopbands in desired spectral locations. Films with a predefined defect in the periodicity have also been designed and fabricated using the GLAD technique. Optical measurements of these samples have shown that the incorporation of a uniaxial defect layer into the film leads to the appearance of a transmittance peak within the stopband. We have performed finite-difference time-domain simulations of light transmission through the optical filters and calculated the photonic dispersion relation of idealized structures. By changing the geometry of the defect, the ability to control the location and width of the transmittance peak in the spectrum has been demonstrated. The theoretical results obtained demonstrate very good agreement with experimental measurements and allow one to make accurate predictions of the optical properties of GLAD fabricated thin films.

Glancing angle deposition was used to produce approximately 150-nm-thick silver nanoparticle films, which were evaluated as localized surface plasmon resonance (LSPR) biosensors. The films have a strong extinction peak around 368 nm in air due to LSPR. As the refractive index of the surrounding environment is increased, the extinction peak red-shifts with a linear dependence. The films were functionalized with 11-amino-1-undecanethiol and rabbit immunoglobulin G (rIgG) to allow for the detection of anti-rIgG binding. Binding of biomolecules to the nanoparticle surface increases the local refractive index and results in a red-shifting of the extinction peak. The wavelength shift at varying concentrations of anti-rIgG was measured and fit to the Langmuir isotherm. This yielded approximate values for the saturation response, Delta lambda max = 29.4 +/- 0.7 nm, and the surface confined binding constant, Ka = (2.7 +/- 0.3) x 10(6) M(-1). The response to nonspecific binding was also investigated.

This contribution highlights correlation between the surface concentration of a chemisorbed organophosphorous probe (flavin mononucleotide) and the relative hydroxyl surface coverage of nanostructured ITO electrodes, which can be tuned during post-deposition reductive annealing. The resulting modified electrodes are very stable in aqueous solution, highly hydrophilic and fully-accessible to the bulk solution.

Glancing Angle Deposition (GLAD) was used to prepare 500 nm long Ni nanopillars directly on glassy carbon disc electrodes (Ni GLAD /GC). Ni GLAD {Pt}/GC core-layer nanopillars were prepared by depositing Pt on the Ni GLAD substrate via a novel rotating disc electrode galvanostatic deposition, where a stationary blackened Pt counter electrode served as the Pt source. Scanning electron microscopy, cyclic voltammetry, and inductively-coupled mass spectrometry were employed to characterize the deposits. Results indicated that the Pt was deposited in a conformal manner on the Ni GLAD giving a loading of 11.6 μg. The Ni GLAD {Pt}/GC electrode was ca. three fold more active than a {Pt}/GC (made with the same deposition in the absence of Ni) towards the oxygen reduction reaction (ORR) in 1.0 M KOH. As well, long term potentiostatic ORR studies showed the Ni GLAD {Pt}/GC deposit was more durable than the {Pt}/GC, with the former completely retaining its initial performance after 5000 s polarization at 0.85 V vs. RHE, while {Pt}/GC lost 38% of its activity. Subsequent control experiments in the absence of O 2 showed that such decay was not due to loss of Pt over the prolonged ORR.

Ultrathin and nanostructured stationary phases potentially enable faster separations over shorter distances with higher sensitivity than that possible with thin-layer chromatography (TLC) or high-performance thin-layer chromatography (HPTLC). The strong dependence of planar chromatography performance on microstructure motivates investigation of new sorbent layers. This chapter surveys innovative stationary phases prepared from monolithic silica gels, monolithic polymers, electrospun nanofibrous polymer mats, nanostructured columnar thin films, and structures templated onto carbon nanotubes. General fabrication approaches and merits are summarized for each method. Implications of these new layers on instrumentation and other techniques are also described. The chapter concludes with a discussion of the future prospects of ultrathin and nanostructured media in planar chromatography.

In this Letter, reflection-mode optical resolution photoacoustic microscopy (OR-PAM) using glancing angle-deposited (GLAD) nanostructured Fabry–Perot interferometers (FPI) for in vivo applications is reported. GLAD is a single-step physical vapor deposition (PVD) technique used to fabricate porous nanostructured thin films. Using titanium dioxide, a transparent semiconductor with a high refractive index (n=2.4), the GLAD technique can be employed to fabricate samples with tailored nano-porosity, refractive index periodicities, and high Q-factor reflectance spectra. The OR-PAM in vivo images of chorioallantoic membrane (CAM) of 5-day chicken embryo model are demonstrated. The phantom study shows lateral resolution and signal-to-noise ratio better than 7 μm and 35 dB, respectively. The sensitive GLAD FPI allows photoacoustic imaging down to a few-nJ pulse energy. To the best of our knowledge, this is the first time that a FPI-based reflection mode optical resolution photoacoustic imaging technique is demonstrated for in vivo applications.