Optical and electrochemical properties of optically transparent,boron-doped diamond thin films deposited on quartz

The optical and electrochemical properties of transparent, boron-doped diamond thin film, deposited on quartz, are discussed. The films were deposited by microwave-assisted chemical vapor deposition, for 1-2 h, using a 0.5% CH4/H2 source gas mixture at 45 Torr and 600 W of power. A high rate of diamond nucleation was achieved by mechanically scratching the quartz. This pretreatment leads to the formation of a continuous film, in a short period of time, which consists of nanometer-sized grains of diamond. The thin-film electrode was characterized by cyclic voltammetry, atomic force microscopy, and UV-visible absorption spectrophotometry. The film's electrochemical response was evaluated using Ru(NH3)6(3+/2+) in 1 M KCl, Fe(CN)6(3-/4-) in 1 M KCl, and chlorpromazine (CPZ) in 10 mM HClO4. The film exhibited a low voltammetric background current and a stable and active voltammetric response for all three redox systems. The optical transparency of the polycrystalline film in the visible region was near 50% and fairly constant between 300 and 800 nm. The optical and electrical properties were extremely stable during 48-h exposure tests in various aqueous (HNO3, NaOH) solutions and nonaqueous (e.g., chlorinated) solvents. The properties were also extremely stable during anodic and cathodic potential cycling in harsh aqueous environments. This stability is in stark contrast to what was observed for an indium-doped tin oxide thin film coated on quartz. The spectroelectrochemical response (transmission mode) for CPZ was studied in detail, using a thin-layer spectroelectrochemical cell. Thin-layer voltammetry, potential step/ absorption measurements, and detection analytical figures of merit are presented. The results demonstrate that durable, stable, and optically transparent diamond thin films, with low electrical resistivity (approximately 0.026 omega x cm) laterally through the film, can be deposited on quartz.     

Optical properties of europium thin films

The optical conductivity of europium was studied between 1.6 and 6.2 eV under static ultrahigh vacuum. It is shown that the total conductivity σ(ω) results from a coupling between frequency-dependent intraband, interband and structure terms. The maxima which are displayed near 2.12 and 4.58 eV are explained by two different mechanisms. The joint density of states is obtained from energy band calculation. In the ultraviolet range the observed peaks agree with the experimental absorption band which is assigned to interband transitions. In the infrared region the structure in the conductivity is thickness dependent and is correlated with granular effects which are explained by means of a refined Maxwell Garnett theory.     

Optical properties of vanadium thin films

The optical constants of vanadium thin films of different thicknesses were determined in the spectral range of 2.5 to 8.5 m. These optical constants were used to evaluate some microcharacteristics of vanadium thin films such as the free charge concentration, the relaxation time, the static conductivity, the electron velocity at the Fermi surface, the mean free path and the specularity parameter.The determination of the microcharacteristics were carried out in conjunction with Drude's theory of free charge carriers as well as with anomalous skin effect theory.     

Optical properties and instrumental performance of thin gold films near the surface plasmon resonance

The optical properties of very thin gold films have been evaluated by Fresnel analysis, with optical boundary conditions pertaining to the surface plasmon resonance (SPR) at the gold-water interface. The experimental SPR characteristic was evaluated in the angular interrogation mode. Film morphology was characterized by high resolution transmission electron microscopy. The magnitude of the resonance, i.e., the SPR signal, sensitively depends on, and is affected by film thickness and morphology. A sharply defined thickness of 55 ± 5 nm is required, to achieve optimum SPR excitation conditions, and instrumental sensitivity. With decreasing film thickness, below 40 nm, the resonance angle starts to shift to larger values. A substantial increase of the intrinsic resonance broadening parameter is observed below 70 nm, associated with an increasingly asymmetric SPR line shape. A similar effect occurs in the presence of a very thin chromium adhesion layer. Surface roughness and film thickness modulations determine the experimentally observed line broadening parameter. Instrumental noise levels largely depend on accuracy and quality at which the resonance angle can be determined. Substantial improvement and instrumental sub-pixel resolution is achievable by optimum fitting routines, accounting for drastic noise reduction and improved instrumental sensitivity, up to two orders of magnitude over the inherent geometric sensor pixel resolution.     

Mammalian cell cultures on micropatterned surfaces of weak-acid, polyelectrolyte hyperbranched thin films on gold

A four-step soft lithographic process based on micro-contact printing of organic monolayers, hyperbranched polymer grafting, and subsequent polymer functionalization results in polymer/n-alkanethiol patterns that direct the growth and migration of mammalian cells. The functional units on these surfaces are three-dimensional cell "corrals" that have walls 52+/-2 nm in height and lateral dimensions on the order of 60 microm. The corrals have hydrophobic, methyl-terminated n-alkanethiol bottoms, which promote cell adhesion, and walls consisting of hydrophilic poly(acrylic acid)/poly(ethylene glycol) layered nanocomposites that inhibit cell growth. Cell viability studies indicate that cells remain viable on the patterned surfaces for up to 21 days, and fluorescence microscopy studies of stained cells demonstrate that cell growth and spreading does not occur outside of the corral boundaries. This simple, chemically flexible micropatterning method provides spatial control over growth of IC-21 murine peritoneal macrophages, human umbilical vein endothelial cells, and murine hepatocytes.     

Magnetic properties of permalloy/permalloy-oxide multilayer thin films

Magnetic properties of permalloy/permalloy-oxide multilayer thin films are investigated. These thin films are prepared by a repeat of sputter deposition of permalloy thin film, followed by oxidation of the film surface. The total thickness of the permalloy thin films before oxidation is about 100 nm. The number of layers is one to twenty. The oxide layers are formed by oxidation in dry air. The estimated oxide layer thickness is about 2 nm. The oxide NiFe₂O₄ is identified by RHEED. The film coercivity decreases linearly with increasing layer numbers. The saturation magnetization and magnetoresistivity decrease as the number of layers increase. The coercivity decrease is due to grain growth suppression and magnetic separation by oxide film of permalloy layer, and magnetoresistivity decrease is due to electrical resistivity increase originating into electron scattering by the oxide layer.     

Optical properties of AgGaSe2 thin films

AgGaSe₂ films were grown using the flash evaporation technique on glass substrates at various substrate temperatures. The optical absorption of these films in the energy range 1.4–1.9 eV was studied and the films were found to possess direct band gap material. The photoconductivity of the AgGaSe₂ films was studied as a function of (i) light intensity, (ii) temperature and (iii) response times. The photoconductivity response spectra of the AgGaSe₂ films were utilized to determine the band gap energies as a function of the substrate temperature. The implications are discussed.     

Optical properties of Langmuir-Blodgett polydiacetylene thin films

The colour phase transition of Langmuir-Blodgett polydiacetylene (LB PDA) films is investigated as a function of annealing temperature. A new reversible colour change is observed for a short annealing time. Such a reversible property has not previously been reported in LB PDA films. The X-ray diffraction patterns show that the reversible property is closely related to the layer structure of the LB films. Furthermore, the ratio of the line intensities of the Raman peaks due to C≡C and C=C stretch modes changes with the annealing temperature. The colour phase transition of the LB PDA films is correlated with this ratio. Such phase transitions have also been observed in laser-annealed points of LB PDA films. From these results, a new optical device based on LB PDA films is proposed. Furthermore, the electrical properties of ion-irradiated LB PDA films are briefly reported.     

Optical properties of CulnSe2 thin films

The optical constants of vacuum-deposited CulnSe₂ films were determined from the measured transmittance and reflectance at normal incidence of light in the wavelength range 500 to 2000 nm. The analysis of the experimental points of the absorption coefficient revealed the existence of two optical transition processes: an allowed direct transition withE _g=1.03±0.01 eV and a forbidden direct transition withE _f=1.254±0.001 eV. The optical constants of the films were independent of the substrate temperature.On leave to the Kingdom of Saudi Arabia.     

Optical properties and structure of thin SiOx films

The optical properties of SiO_x films of variable composition obtained by reactive r.f. sputtering of silicon were investigated.The experimental results show that the films have a single-phase structure consisting of a continuous random network with a dominance of six-membered molecular rings of Si-(Si_yO_4-y tetrahedra, where 0⩽y⩽4, joined together by bridging oxygen atoms. The difference between the films investigated and those obtained by vacuum evaporation is determined by the dominance of four-membered rings in the evaporated films.Analysis of the IR spectra reveals that the shift in the absorption band with varying structure is connected with a variation in the central force constant.     

Optical properties of porous helical thin films

Porous dielectric thin films, composed of isolated helical columns, are fabricated by the glancing angle deposition technique. The selective reflection of circularly polarized light and the optical rotation of linearly polarized light are investigated as a function of film material and helical morphology. The strongest chiral optical response is observed for titanium-dioxide films because of its large refractive index. Optical rotatory powers as high as 4.5 degrees are observed in 830-nm-thick helical films. By tailoring the pitch of the helical columns, the wavelength dependence of the circular reflection band is tuned to preferentially reflect red, green, or blue light, a promising quality for display applications.     

Review Composite and multilayer ferroelectric thin films: processing, properties and applications

This paper reviews recent developments in processing, properties and applications of composite and multilayer ferroelectric thin films. Methods such as physical vapor deposition, chemical vapor deposition and sol-gel, for the processing of composite and multilayer ferroelectric films are described. Among the techniques reviewed for the fabrication of multilayer ferroelectric films, molecular beam epitaxy and atomic layer metal-organic chemical vapor deposition are the most suitable techniques for the deposition of superlattices with atomically sharp interface. As an efficient and quick way, pulsed-laser deposition has been widely used for the preparation of ferroelectric multilayers and heterostructures. Superior dielectric properties have been reported for sol-gel-derived micrometer-thick ceramic/ceramic composite ferroelectric films. Properties of multilayer ferroelectric films vary as a function of periodicity, which can be exploited for the development of various electronic devices. Enhanced characteristics of composite and multilayer films with selected examples from recent literature and the origin of enhancement are discussed and summarized. Finally, applications of the materials for the development of various electronic devices are also presented.     

Interfacial energy induced microstructure of thin magnetic iron/gold multilayer films

Magnetron sputtered iron/gold multilayers are investigated by cross-sectional transmission electron microscopy. Thermodynamic considerations can explain the different observed microstructures near the substrate and near the top of the multilayers.     

Optical properties of amorphous, erbium-doped yttrium alumino-borate thin films

In this paper, we report on the optical characterizations of erbium-doped yttrium alumino-borate glassy thin films prepared by the polymeric precursor and sol-gel routes and the spin-coating technique. High quality planar waveguides were produced by a multilayer processing of Y_1−xEr_xAl₃(BO₃)₄ compositions with x = 0.02, 0.05, 0.10, 0.30, and 0.50. Their optical properties were investigated using transmission, photoluminescence, and m-lines spectroscopy, whereas high resolution scanning electron microscopy (HR-SEM) was applied to check film thickness and surface homogeneity. The refractive indices determined from transmission and m-lines spectroscopy are in good agreement just like the film thickness measured by HR-SEM and transmission spectroscopy. We observed low propagation losses, together with efficient photoluminescence emission for polymeric precursor thin films, involving low cost and environment friendly reactants.