Metal containing diamond like carbon coatings (Me-DLC) are well known for their excellent tribological properties. They have a great potential in the field of wear and friction reduction on precision components. The importance of this coating material is increasing continuously in a wide range of applications. However, the wear resistance of standard Me-DLC coatings is still markedly lower than that of pure diamond like carbon (DLC). Today, the deposition of pure DLC in an industrial scale as well as its adhesion are still on research. On the contrary, dc magnetron deposition techniques for Me-DLC coatings show excellent adhesion and have reached a high technological level. The aim of our work was to close the quality gap between Me-DLC and DLC, especially with respect to wear resistance. The preparation of the Me-DLC coatings were performed in an industrial batch coater by reactive dc magnetron sputtering in an argon acetylene mixture using Ti, W and WC/Co targets. A comparison of the deposition rates, wear and adhesion of the coatings deposited using the different targets is presented. Besides the coating properties, aspects like process stability and target costs will be discussed.

Heterostructures formed from III-V semiconductors with the 6.1 angstroms lattice spacing (InAs, GaSb, AlSb and related alloys) have attracted significant interest because of their potential to define a new `state of the art' in applications including 100 GHz high-speed logic circuits, terahertz transistors, sensitive infrared detectors and mid-infrared semiconductor lasers. In this paper, we describe the ongoing work at the Naval Research Laboratory to develop the materials growth and fabrication technology for a variety of 6.1 angstroms-based devices which have the potential to revolutionize infrared optoelectronics and low-power, high- speed electronics.

Optical lithography is one of the key enabling technologies in semiconductor microcircuit fabrication. As the demand for devices with higher performance and speed continue, the need for patterning circuits with finer features is driving optical microlithography to shorter and shorter wavelengths (248 nm yields 193 nm yields 157 nm). This is because the resolution with traditional Cr masks, that either block or pass light for imaging, is limited by optical diffraction. At any wavelength, however, phase-shift masks can enhance resolution beyond the wavelength-imposed diffraction limit. Phase-shift masks work by employing destructive optical interference to enhance contrast. This paper discusses a novel, systematic materials approach--optical superlattices- -to design embedded attenuating phase-shift masks, the most versatile and common type phase-shift mask, for any optical wavelength. These superlattices are comprised of alternating, ultrathin (< 10 nm) layers of an optically transparent compound multilayered with an optically absorbing one, e.g., Si₃N₄ and TiN. Film structure, optical properties, etching, chemical stability, and radiation durability are discussed.

Composite aerogels are nanoscale mesoporous materials that retain both the meso- and nanoscopic properties of each component. Colloidal metal-silica aerogels (in which the colloidal metal is Au or Pt) exhibit both the transparency and porosity of silica aerogel and the optical behavior of the metal colloid. The silica aerogel essentially acts as a transparent matrix for the isolated metal colloids, which remain accessible to external reagents. Sensing elements adsorbed to the surface of the metal in colloidal Au-silica aerogels are also addressable. For dyes with absorption spectra complementary to that of the metal plasmon resonance, spectral changes due to alteration of the dye environment may be optically monitored. By dispersing the metal colloids in an about-to-gel silica sol, the properties of the metal colloid (i.e. size, which determines the position and FWHM of the plasmon resonance) can be tailored prior to immobilization. The ability to modify the colloidal metal surface either prior to or following gelation in the silica matrix coupled with gentle processing conditions permit modification of the metal surface with, for example, temperature-sensitive biomolecules. Composite colloidal metal-silica aerogels therefore provide a novel method for the nanoscale engineering of optical sensors with rapid response times due to the high mesoporosity of the silica matrix.

We analyze microstructure, linear and nonlinear optical properties of planar waveguides produced by implantation of MeV Ag ions into LiNbO₃. The linear optical properties include spectrum of propagation modes, and optical absorption spectrum. The nonlinear properties include optical spectrum of nonlinear refractive index. Operation of the implanted crystal as an optical waveguide is due to modification of the linear refractive index of the implanted region. The samples as implanted do not show any light guiding. Heat treatment of the implanted samples makes planar light guides on the implanted surface. High- resolution electron microscopy reveals recrystallization of the host between the surface and the nuclear stopping region in the form of randomly oriented micro crystals. They make up a light guiding layer isolated from the bulk crystal by the low index nuclear stopping layer. Optical absorption has a peak at 430 nm. This peak is due to the surface plasmon resonance in metal nanoclusters formed in the host after implantation. Heat treatment of the silver implanted samples shifts the absorption peak to 550 nm. Relatively strong third order nonlinearity of the samples is due to the three orders of magnitude enhancement of the intrinsic intraband and interband electron component of polarizability in the vicinity of the surface plasmon resonance. The nonlinear refractive index of the samples (of the order of 10^-10 cm²/W) was measured with the Z-scan technique using a picosecond laser source. Possible applications of the waveguides include ultra-fast photonic switches and modulators.

The intensities of electro- (EL) and photoluminescence (PL) in graded-bandgap semiconductor structures operating in the double injection mode are calculated. The cases of the band- to-band radiative recombination and radiative recombination via centers are considered. The dependencies of the intensity of luminescence on current and incident radiation intensity for different lengths of the base and energy bands gradients are analyzed. It is shown that linear, quadratic or cubic dependencies for the EL intensity on current with smooth transitions between them are possible for the band- to-band radiative recombination case. In the dependence of the PL intensity on incident radiation intensity, besides the linear term, there is a quadratic one getting sharper with an increase in the current.

This paper provides a basic introduction into the electromagnetics of complex materials. It is shown how Maxwell's differential equations must be supplemented by constitutive relations which describe the specific electromagnetic properties of a complex material. Field equations will be derived and a solution representation in terms of dyadic Green functions is given. Finally, special emphasis is put on materials which exhibit a microstructure that is rotationally nonhomogeneous. Various types of thin films and, in more generality, helicoidal bianisotropic mediums, provide the most prominent representatives of such materials. A closed-form solution for the dyadic Green functions of a helicoidal bianisotropic medium is given when the coordinate dependence is restricted to the helicoidal axis only.

The concept of nanoscopic-to-macroscopic homogenization of a sculptured thin film (STF) into a unidirectionally nonhomogeneous continuum is presented. The global constitutive properties of linear STFs are connected to the so-called local or reference constitutive properties by rotation dyadics. The local properties are obtained using the Bruggeman formalism for dielectric as well as bianisotropic STFs. Limitations of the presented approach are discussed, and some avenues for further theoretical research are suggested.

We describe experimental measurements of the optical scattering properties of metallic surfaces with nanometer- scaled roughness. The surfaces are fabricated using microlithographic techniques and are fully characterized with surface profilometry. The surface roughness is carefully designed so that when illuminated with laser light, surface plasmon polaritons are strongly excited; these are then again scattered by the roughness and converted into diffuse light escaping from the surface. In the diffuse scatter, unusual features are observed that are attributed to the plasmon polariton excitation. For example, backscattering enhancement arising from constructive interference between polariton-related scattering processes dominates the scattering distribution in some cases. Also discussed are experimental results for second harmonic generation from rough metal surfaces, where the consequences of polariton excitation at both the fundamental and harmonic frequencies are observed. If the surface producing strong fundamental plasmon excitation lead to stronger harmonic generation and quite different scattering distributions. Finally, experiments with quasiperiodic surfaces, both in the linear and second-harmonic cases, produce effects that are shown to be related to those observed with rough surfaces.

More than 10 years ago, birefringent films of metal oxides were formed by oblique vapor deposition and investigated with a view of their application to optical retardation plates. The retardation function of the films was explained in terms of the birefringence caused by the characteristic anisotropic nanostructure inside the films. These films are now classified in the genre of the so-called sculptured thin films. However, the birefringent films thus prepared are not yet industrialized even now due to the crucial lack of the durability and the yield of products. In this review paper, we describe the present status of application process of the retardation films to the information systems such as compact disc and digital versatile disc devices with a special emphasis on the uniformity of retardation properties in a large area and the stability of the optical properties of the obliquely deposited thin films. Finally, further challenges for wide application of the obliquely deposited thin films are also discussed.

When thin films are deposited from plasma with a significant a degree of ionization or under ion bombardment, the energy of the incident ions can be used as an effective means for engineering microstructures. Ion energy has been increasingly used as a deposition parameter. The introduction of plasma immersion ion implantation has made ion-assisted processes more amenable for industrial implementation because it has diminished the complexity of hardware, and allowed larger areas and complex shapes to be treated. Here we discuss the impact of energetic particles on the microstructure and properties of films produced by filtered cathodic arc (FCA) and magnetron sputter (MS) deposition with ion assist. Amorphous hard carbon films with high content of sp3-hybridization were prepared using both techniques under optimum ion bombardment conditions to maximize the content of tetrahedral-bonded carbon. Techniques for controlling film properties by altering the nano-structure are presented. The effect of energetic particles on conventional and sculptured thin-films is also discussed and examples of metallic and ceramic films are presented and discussed in light of atomic mechanisms.

Unique thin film microstructures have been fabricated with the Glancing Angle Deposition (GLAD) technique. These porous, thin films can be engineered with a variety of different morphologies to sub-micron dimensions, including helical, post, and chevron or zigzag microstructures. This paper reports some recent results in study and application of films deposited using GLAD, namely: the use of low pressure, long throw sputtering to produce porous titanium films; deposition of porous, structured ZrO₂ films for use as thermal barriers; and measurement of the mechanical response of chiral or `microspring' thin films.

Sculptured thin films (STFs) are columnar thin films in which the growth direction is altered instantaneously by variations in the vapor incidence angle. By fixing the orientation of the substrate-surface to a glancing angle (approximately 1-30° from the substrate plane) where atomic self-shadowing effects are enhanced, and then rotating around the plane normal, it is possible to engineer a wide range of STF nanostructural shapes which have been classified generally as thin film helicoidal bianisotropic mediums (TFHBMs). If the column size remains constant with increasing film thickness (i.e. matchstick morphology), then the TFHBMs will have constant density with evolution, and existing theories can describe their optical behavior. Furthermore, many practical applications will require constancy with evolution. In this paper we show that essentially constant column size (widths are typically 10 - 100 nm) is obtained for simple motions of the substrate for TFHBM growth, whereas more complex motions involving rapid and abrupt changes in the angular velocity result in column size increases with evolutionary development (widths up to 200 - 500 nm for film thicknesses of 2 - 4μm). As the column sizes approach optical wavelengths, the assumption that the STF is a rotationally non-homogeneous continuum is invalid and will lead to complicated optical behavior and modeling. A classification scheme is proposed to understand the underlying mechanisms for column expansion, and it is based upon the deposition parameters of column growth rate in the column direction, angular rotation rate, and the vapor incidence angle, and their combined effects on the anisotropy of the atomic self-shadowing process. Approaches to controlling and possibly eliminating this column expansion are discussed and include ion bombardment during growth and its effects on the shadowing processes.

A class of hydrogels with microstructural surface arrays has been synthesized. The sputter-depositing method is used to imprint the surface of an N-isopropylacrylamide (NIPA) gel with a square array of a gold thin film. The periodicity of the array is about 20 μm and can be varied as a function of temperature or electric field. As the periodicity of the gel surface pattern changes in responsive to the external stimuli, the light diffraction pattern changes accordingly. It is demonstrated that the deformation of a gel under external force can be easily monitored using the gel with the periodic surface array. The temperature-responsive NIPA polymer gel is also deposited on the surface of another non- responsive gel using the method of photosensitized solution polymerization. The patterned area can be rendered invisible reversibly by switching the temperature above or below the low critical solution temperature of the NIPA gel. Furthermore, the patterned area can also change its hydrophilicity with the environment. The gels with engineered microstructural surface patterns may find applications in sensor and display technology.

Surface scattering of Si to enhanced absorption particularly in the IR spectral region has been extensively investigated. Previous research chiefly examined approaches based on geometrical optics. These surface textures typically consist of pyramids with dimensions much larger than optical wavelengths. We have investigated a physical optics approach that relies on surface texture features comparable to, or smaller than, the optical wavelengths inside the semiconductor material. Light interaction at this are strongly dependent on incident polarization and surface profile. Nanoscale textures can be tuned for either narrow band, or broad band absorptive behavior. Lowest broad band reflection has been observed for triangular profiles with linewidths significantly less than 100 nm. Si nanostructures have been integrated into large (approximately 42 cm²) area solar cells. Internal quantum efficiency measurements in comparison with polished and conventionally textured cells show lower efficiency in the UV-visible (350 - 680 nm), but significantly higher IR (700 - 1200 nm) efficiency.

Composite dye/superconductor sensors which can discriminate different wavelengths of light in the visible and near- infrared regions have been fabricated. By lithographically patterning 1500 angstroms thick films of the superconductor YBa2Cu3O7_-δ on MgO substrates, arrays of microbridges have been created. A layer of dye dispersed in a polymeric matrix is deposited on top of each bridge to create the wavelength selective light absorbing element. Each meandering path bridge is approximately 20 μm wide and approximately 10 mm long. The device functions in a different manner to traditional semiconductor-based light sensing technologies in which a dye structure serves the role of a filtering agent. Here, the response of the hybrid dye/superconductor element is amplitude at wavelengths strongly absorbed by the dye laser. Such devices represent the initial steps towards a larger structure capable of simultaneously sensing wavelength bands from the visible through to the infrared. In addition to dye sensitization method, another approach to adding wavelength selectivity to detectors is described here in which interference effects in micromachined microbolometers are exploited.

Clusters of CdS were prepared inside the framework voids of zeolites NaX and chabazite by multistage ion exchange chemical reaction. It was observed that each stage of reaction affects the structure of zeolites crystals. Aluminum atoms change their coordination state at the first stage because of hydrolytic decomposition of some Al-O tetrahedral bonds. Partially reversible relaxation of aluminum atoms of zeolite framework occurs during the second stage of chemical reaction. This spontaneous transition of the coordination number of aluminum atoms took place without changing of their positions of framework atoms. Such kind of the interaction between framework atoms of alumosilicates and doping ions, which are precursors of the clusters in the zeolite hosts, give indirect information about mechanism of the `ship-in-the-bottle' synthesis of semiconductor materials.

Glancing angle deposition (GLAD), developed recently by Robbie and Brett, is an advanced technique of thin film deposition that can produce porous thin films with columnar microstructural features controllable on a ten nanometer scale. GLAD combines highly oblique angle deposition with computer controlled substrate motion to allow engineering of thin film microstructure for a diverse range of applications. Of particular promise for optical applications are chiral thin film morphologies, including films fabricated by GLAD possessing helical microstructure. Previous optical characterization has demonstrated rotation of the plane of polarization in these films. In this work, circularly polarized spectroscopic transmission measurements on helical GLAD films have shown selective reflection/scattering of the circular polarization which matches the handedness of the film, with the helical pitch controlling the peak wavelength. The geometric properties of films fabricated with GLAD, such as film density, helical rise angle, and helical radius can be controlled independently and easily allowing optical properties to be tailored as desired.

Thin film form birefringence depends on the shape or bunching of nanostructural columns and on the difference in the refractive indices of the columns and the surrounding voids. When moisture from the atmosphere enters the nanostructure the linear form birefringence may decrease by a large amount, of the order of 50%. However, current data refers to tilted-columnar films. We report here on moisture penetration effects in films fabricated by serial bideposition and engineered for large linear form birefringence or large circular form birefringence. As well, we consider post-deposition processes that may retard the uptake of moisture. Vacuum deposition results in oxygen deficient surfaces which rapidly absorb oxygen from the atmosphere either in the form of O₂ or H₂O. In order to retard water uptake this deficiency must be reduced, possibly by annealing samples in an oxygen rich atmosphere subsequent to deposition. Alternatively, surface oxide and hydroxyl groups can be rendered hydrophobic via reaction with silane derivatives. Both methods have been tested for their effectiveness in retarding water uptake.

As sculptured thin films (STFs) have a nano-engineered morphology (comprising 3 - 5 nm clusters) STFs with desired electromagnetic properties in the optical, infrared, millimeter wave and even microwave regimes can be tailored. With the development of specialized fabrication techniques on the upswing, device-oriented studies on STFs are gaining impetus. We focus on five possible applications of STFs: (1) laser mirrors and notch filters, (2) rugate-like filters, (3) optical gas concentration sensors, (4) optical interconnects, and (5) ultra-low permittivity barriers.

The purpose of the present work was to study antiviral activity and the structure of two medical preparations (collargol and protargol) containing silver particles and clusters. Optical properties, particle size distribution and oxidation state of silver particles were investigated by means of the diffuse reflectance electron spectroscopy, high resolution electron spectroscopy, small angle x-ray scattering, auger-electron spectroscopy and x-ray diffraction. Investigation of both preparations in vitro showed that antiviral activity calculated per one gram of silver for collargol is higher than that for one protargol by coefficient ca. 1.5. These two preparations showed significant difference in particle size distribution and small cluster contribution. In protargol, small silver clusters with size ca. 1 nm predominate, while in collargol the size of predominant particles is essentially higher. In collargol, silver is predominantly in metallic state while in protargol either in metallic or oxidized states. Fast oxidation of small silver clusters in protargol was observed in aqueous solution. It is suggested that the silver clusters do not play the leading role in antiviral action of the preparations. Possible mechanism of antiviral activity of the silver particles is discussed.

We propose the molecules B₁₂N₁₂, B₂₄N₂₄ and B₆₀N₆₀ (named us as fulborenes) in the capacity of boron nitride analogues of the fullerenes. Ten possible crystals built from these molecules (named us as fulborenites) are predicted, including `superdense diamond', and their lattice parameters and densities are calculated. Comparison with explosive experiments allow us to identify the simple cubic fulborenite B₁₂N₁₂ with intermediate phase of BN. Multiwalled BN-nanotubes are produced by carbothermal synthesis, and their structure are studied by TEM, x-ray spectral microanalysis and molecular dynamic techniques.

By using femtosecond time-resolved pump-probe technique we have observed three kinds of coherent phonons (0.30 THz, 1.90 THz, and 3.75 THz) in silver nanoparticles embedded in BaO thin films. The generation of 0.3 THz coherent phonons is attributed to the resonant excitation of localized surface plasmon of silver nanoparticles, and the resonant impulsive stimulated Raman scattering in silver aggregates is responsible for the generation of 1.90 THz and 3.75 THz coherent phonons. But in another area in the same Ag-BaO thin film we only observe 0.3 THz coherent phonons. The space dependence of coherent phonons is attributed to the inhomogeneous distribution of (Ag)_n aggregates.

Compositions of highly ordered trans-nanopolyacetylene (trans-NPA) were prepared in the form of solutions, films and plates. They are characterized by the high stability and vibrational structure of the cis and trans bands in UV-Vis absorption spectra. There are five basic features that distinguish the Raman scattering by the trans-NPA compositions from the Raman scattering by the standard trans-PA modification. (1) Extremely low intensity of fluorescence at excitation in visual region. (2) The weak frequency dispersion of polyene C=C and C-C stretching bands, which is evidence for the narrow length distribution of conjugation chains. (3) The occurrence of long sequences of overtones and combination bands in room- temperature resonance and off-resonance Raman spectra. (4) High intensities of the anti-Stokes lines of the fundamentals v₁ and v₃ of the polyene chain. (5) Extremely high intensities of the v₁ and v₃ fundamentals of the polyene chain.

The silica antireflective film doped PEG (polyethylene glycol) and siloxane into aged base-catalyzed colloidal SiO₂ suspension has been formed. It is illustrated that its laser induced damage threshold and scratch-resistant capability have been improved, and the film can be also used for a longer time in practical applications. By means of investigation of the surface structure, transmission spectrum and laser damage threshold of the film. The role of the siloxane is analyzed.

The properties of anisotropic coatings fabricated in vacuum by serial bideposition are described. With appropriate choice of deposition parameters the technique can be used to engineer large linear form birefringence in films that have nanostructural columns aligned perpendicular to the surface of the substrate. Conversely, the biaxial films can be engineered so that all principal axes are inclined to the substrate, or the target of engineering can be large circular form birefringence. Several general and specific applications are discussed, including the fabrication of waveplates, linear polarizers, and a double-layer anisotropic antireflection coating used to select the polarization direction of an open cavity HeNe laser.