Crystal Quartz Substrates Research Articles

Molecular recognition of Langmuir–Blodgett polymer films containing uracil groups

Novel copolymers, poly(acryroyloxymethyluracil-co-hexylacrylamide)s (poly(AU-co-HAAm)s), have been synthesized by radical copolymerization with different monomer ratios. The poly(AU-co-HAAm)s formed stable monolayers at the air–water interface and could be deposited on solid substrates as Y-type films by the vertical dipping method. The molecular structure of poly(AU-co-HAAm) LB films was determined by reflection absorption and transmission FT-IR, and X-ray diffraction measurements. Evidence for preferential orientation of both the AU and HAAm units was found. The LB films deposited on quartz crystal microbalance substrates adsorbed adenosine molecules, and the adsorbed amounts increased with higher contents of uracil groups in poly(AU-co-HAAm)s. Some morphology changes of LB films were also observed by atomic force microscopy (AFM) after the molecular recognition.

Investigation of Novel Surface Acoustic Wave (SAW) Gas Sensor Used in Sensor Network

Mobile communications, e.g., cellular phones, have become very widespread. A new concept called \Sensor Network has been proposed with the development of such commu- nications system. Sensed signals from many sensor nodes installed in a wide area are gathered to a center node by technology similar to that used in mobile communications. Home/o-ce circum- stance control, environment monitoring and protection can be conducted based on the collected data. We propose a new SAW subtle-gas sensor, which can be used in these sensor nodes. The new sensor structure removes a limited selection for piezoelectric crystal substrates, while only Quartz crystal substrates have been used in conventional SAW gas sensors. The sensing dynamic range was widely extended by utilizing both fundamental and 3rd-harmonic frequency SAWs. Moreover, our sensors are also designed to be combed with 2.4-GHz ZigBee, which has been regulated by IEEE802.15.4, and ZigBee Alliance as a wireless-communications medium for the \Sensor Network. It is predicted that our network system will possibly provide hydrogen-gas leakage sensing for future fuel-cell cars and environmental-pollution gas sensing.

Fabrication of a novel 1,3-bis(p-hydrazonobenzoicacid)indane Langmuir–Blodgett film and organic vapor sensing properties

Abstract A novel 1,3-bis( p -hydrazonobenzoicacid)indane (HBI) molecule was synthesised for the study of monolayer properties at the air–water interface, the fabrication of a Langmuir–Blodgett film, and the investigation of organic vapor sensing properties. Langmuir properties of HBI were studied by taking an isotherm graph. Two different surface pressures were selected for the fabrication of multilayer LB films that were deposited onto glass and quartz crystal substrates. UV–vis spectroscopy and a quartz crystal microbalance (QCM) measurement system were employed to monitor the deposition quality under the two selected deposition pressures. Our results showed that a uniform and high quality LB film with a transfer ratio of 0.96 occurred using the HBI material at a deposition pressure of 22.5 mN m −1 . The LB film deposited onto the quartz crystal was used to study the interaction of the HBI material with different organic vapors such as chloroform, benzene, toluene, ethyl alcohol and isopropyl alcohol. Our results show that the HBI material is suitable to produce an organic thin LB film. Our results indicate that the HBI LB film is highly sensitive to chloroform vapor with a fast and reversible response. This new HBI material could be used as a vapor sensing material.

Technique and results of measuring surface-acoustic-wave reflection coefficients with the use of laser sounding

A technique of measuring the surface-acoustic-wave (SAW) reflection with the use of a laser sounding facility containing a reference diffraction grating is described. The characteristics of the SAW reflections from the edges of YX-cut quartz-crystal substrates with the end faces beveled at various angles are measured. In addition, the frequency dependence of the magnitude of the SAW reflection coefficient for reflection from periodic gratings in the form of lithium niobate metal strips are measured.

A study of PVDF Langmuir‐Blodgett thin film using quartz crystal microbalance

AbstractPoly(vinylidene fluoride) (PVDF) was deposited onto a quartz crystal microbalance (QCM), using a standard Langmuir–Blodgett (LB) thin film deposition procedure. QCM technique was used to monitor the reproducibility of the LB film monolayer, and the fabricated QCM sensor was employed to detect the dimethyl methyl phosphonate (DMMP) vapor, a simulant of nerve agents. The results show that PVDF was successfully deposited from the water surface onto the quartz crystal substrate. The PVDF LB film is found to be highly sensitive to DMMP vapor, and frequency shifts are linear to the concentrations. The response of the sensor against DMMP is fast, large, and reversible. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

PLD-grown Yb-doped Sesquioxide Films on Sapphire and Quartz Substrates

This paper focuses on the fabrication and characterization of crystalline Yb-doped sesquioxide films (Yb2O3, Yb:Lu2O3, Yb:Sc2O3) grown by pulsed laser deposition on single crystal sapphire (α-Al2O3) and quartz (α-SiO2) substrates as well as on lutetia (Lu2O3) and scandia (Sc2O3) substrates. Such ytterbium doped active films can be promising for use in a thin-disk laser setup. X-Ray diffraction measurements show that the films grow highly textured along <111> direction. The ω-scan (rocking curve) shows deviation of the crystallite orientation ∼4° in case of Lu2O3 and Yb2O3 films and <1° for Sc2O3 films. Yb2O3 films reveal no luminescence at room temperature and the well known Yb3+ emission in the 975-980 nm region (zero-phonon line) can only be observed at temperatures below 20 K. A similar effect is observed in a bulk Yb2O3 crystal. Ytterbium emission and excitation spectra measured at room temperature for Yb(5%):Lu2O3 and Yb(4%):Sc2O3 films resemble those of the bulk crystal very closely. Luminescence decay lifetimes are also comparable to those measured in a bulk crystal. This indicates a high quantum efficiency of the Yb3+-emission and allows application of such films as active media for thin disk lasers.

Water adsorption on lubricated fullerene-like CN x films

Humidity influences the tribological performance of the head–disk interface in magnetic data storage devices. In this work we compare the uptake of water of amorphous hydrogenated carbon (a-CHy) an ...

High-tone bulk acoustic resonators on sapphire, crystal quartz, fused silica, and silicon substrates

High-tone bulk acoustic resonators (HBARs) have been fabricated on four types of substrates: c-axis sapphire, AT-cut crystal quartz, fused silica, and ⟨100⟩ single crystal silicon. Quality factors of the HBARs on the four substrates have been compared. Temperature effect on the Q and resonant frequency of the four types of HBARs has been investigated. This paper reports that acoustic absorption in fused silica decreases with increased temperature. Acoustic absorptions in the other three substrates increase with increased temperature. Also, temperature coefficients of frequency of HBARs on sapphire, crystal quartz, fused silica, and silicon have been investigated. Finally, acoustic velocities in the four substrates have been extracted by measuring the frequency difference between two successive resonances of the HBAR on the corresponding substrate, and their dependences on temperature have been investigated.

A study of Langmuir–Blodgett thin film for organic vapor detection

In this work, arachidic acid was deposited onto a quartz crystal using a standard Langmuir–Blodgett (LB) thin film deposition procedure. Quartz Crystal Microbalance (QCM) technique was used to monitor the reproducibility of the LB film monolayer and was employed to study the organic vapor sensing properties of chloroform, toluene, benzene, ethyl alcohol and isopropyl alcohol. QCM results show that arachidic acid monolayer was successfully organised and deposited from the water surface onto a quartz crystal substrate. This LB film is found to be highly sensitive and selective to chloroform vapor than other vapors. The response of the sample against chloroform is fast, large and reversible.

Temperature Characteristics of Substrates for Lamb-Wave-Type Acoustic Wave Devices

In this study, we examined the temperature characteristics of a Lamb wave propagating on a thin quartz crystal substrate. Consequently, we found a new cut where frequency hardly changes with temperature. The steady frequency–temperature characteristics show a quadric curve and the third curve. The analytical results and experimental results for the temperature characteristics of a Lamb wave propagating on an AT cut quartz are compared and discussed in this study. The agreement between the theoretical and experimental results shows that the analytical results of this study were reliable.

Femtosecond laser assisted etching of quartz: microstructuring from inside

In quartz crystal substrates, microchannels were made by femtosecond laser assisted etching, i.e., irradiation of focused femtosecond laser pulses followed by wet etching. By the use of wet etching, the laser irradiated region was selectively etched out, and a microchannel was formed inside the quartz substrate. The laser irradiated region was found to be amorphous by transmission electron microscopy. Anisotropy in the etching rate inside the quartz was observed.

Formation of Langmuir–Blodgett thin film of a novel N-dodecylphthalimide

Abstract The aim of this work is to investigate the Langmuir–Blodgett (LB) thin film preparation of a novel N -dodecylphthalimide (NDP). Langmuir properties of this new molecule are studied at the air–water interface recording isotherm graph. Atomic Force Microscopy and Quartz Crystal Microbalance measurement systems are employed to study the LB film deposition process. This newly synthesized NDP molecule can be used as an LB film material and a uniform LB film monolayer at the water surface can be transferred with a transfer ratio of over 0.90 onto a glass or quartz crystal substrates.

Rotating ring-disk electrochemical quartz crystal microbalance: a new tool for in situ studies of oxide film formation

A rotating ring-disk electrode has been made by sputter depositing the disk and ring materials onto a quartz crystal substrate through masks. The design provides for separate electrical leads to ring and disk on the quartz surface. The collection efficiency determined experimentally with ferricyanide was not significantly affected by the presence of the leads. The new RRD electrode design permits the development of a a rotating ring-disk electrochemical quartz crystal microbalance electrode (RRD/EQCM) device for the simultaneous measurement of the disk current, the frequency shift of the quartz crystal and the ring current. The collection efficiency for oxygen was studied with gold disk and ring electrodes and was found to be significantly lower than that for ferricyanide. Using a titanium disk in combination with a gold ring, potential sweep experiments using the RRD/EQCM were carried out on the anodization of titanium in sulfuric acid. Above a potential of 3 V a mass loss was observed at the disk and oxygen was detected at the ring.

A cryogenic post dielectric resonator for precise microwave characterization of planardielectric materials for superconducting circuits

A novel dielectric resonator operating at cryogenic temperatures (14–85 K)at a frequency of 10 GHz for measurements of permittivity and loss tangentof dielectric substrates for HTS microwave circuits is presented. We havefabricated a prototype post dielectric resonator, with superconducting(DyBa2Cu3O7) end plates and silver-plated copper sidewalls to improve the sensitivity andresolution of loss tangent measurements. Also a numerical technique forcalculations of permittivity and loss tangent from the resonant frequency and theQ-factor is presented in the paper. For verification of the technique, measurements of the realpart of the permittivity of a single crystal quartz substrate have been performed and a verygood agreement with published data using the whispering gallery mode technique has beenobtained.

Mathematical models of a biosensor

This paper studies mathematical models of a biosensor that serves for the measurement of small amounts of certain substances in liquids. The device works as follows: acoustic shear waves are excited due to an alternate voltage applied to electrodes deposited on a quartz crystal substrate; the waves are transmitted into a thin isotropic guiding layer in contact with a liquid containing molecules to be detected; these molecules adhere to a specific receptor, aptamer, immobilized on the surface of the guiding layer; the arising mass loading causes a phase shift in the electric signal which is measured on output electrodes. We state a three-dimensional mathematical model that describes a composite structure consisting of three coupled layers: two solid layers with different elastic and electric properties and a liquid layer treated as a weakly compressible viscous fluid. The full coupling between deformations and the electric field is assumed. A two-dimensional model is derived from the three-dimensional one by neglecting the non-homogeneity in x 2 -direction. Another two-dimensional model is derived by the averaging of the three-dimensional model in x 3 -direction under the assumption of an exponential attenuation of waves in the liquid and the substrate. The models are implemented numerically with finite elements. Computer simulations exhibit a good agreement with physical experiments.

Na 0.5 K 0.5 NbO 3 thin films for voltage controlled acoustoelectric device applications

Perovskite Na0.5K0.5NbO3 (NKN) thin films have been prepared on Y+36° cut single crystal quartz substrates using the pulsed laser ablation technique. X-ray diffraction θ–2θ and ω-scan data demonstrate almost perfectly c-axis oriented film textures with narrow mosaic broadening. Radio frequency dielectric spectroscopy showed that the films possess relatively high dielectric permittivities, low dielectric losses, and low frequency dispersions. Capacitance–voltage (C–V) measurements for a 2 μm slot NKN/quartz interdigital capacitor yield 23.1% tunability by applying 40 V bias at 1 MHz, while C–V hysteresis indicates polarization reversal. The considerable voltage tunability with superior crystallinity in piezoelectric NKN films on quartz substrates suggests their potential use for novel voltage tunable acoustoelectric devices.

A novel Love-mode device based on a ZnO/ST-cut quartz crystal structure for sensing applications

A novel Love-mode surface acoustic wave (SAW) sensor with ZnO guiding layer and 90° rotated ST-cut quartz crystal substrate will be presented. Analysis of this device with different thicknesses of ZnO films was undertaken. It will be shown that this novel structure offers distinct advantages over previously fabricated Love-mode structures. These advantages include significantly high sensitivity, small temperature coefficient of frequency and high electromechanical coupling coefficient.

Hydrothermal Liquid Phase Epitaxy of Gallium Orthophosphate on Quartz Crystal Substrates

Gallium orthophosphate (GaPO 4 ) layers for surface acoustic wave (SAW) and sensor applications have been grown on quartz crystal substrates with sizes of about 30 x 30 mm 2 by hydrothermal liquid phase epitaxy (HLPE). The growth of epitaxial GaPO 4 layers is difficult because of a strong tendency for twinning. Besides, a retrograde solubility and an intense chemical aggressiveness of the solution has to be considered. Nevertheless, we found an effective crystal growth technique to deal with these problems using large and qualitatively good substrate crystals of quartz. The most important step of the epitaxy is the formation of an interlayer between the quartz substrate and the GaPO 4 deposit. Epitaxial layers with thickness up to 500 μm were obtained and characterised by means of X-ray techniques.

Cholesterol biosensors prepared by layer-by-layer technique

The analysis of formation, deposition and characterization of cholesterol oxidase (COX) layer-by-layer films were performed. Initially, a layer of polyanion, poly(styrene sulfonate) (PSS) was adsorbed followed by a layer of polycation, poly(ethylene imine) (PEI) on each solid substrate from aqueous solutions. The alternating layers were formed by consecutive adsorption of polycations (PEI) and negatively charged proteins (COX) and cholesterol esterase (CE). A strong interaction between protein and polyelectrolyte improves the stability of the alternating multilayer; however, it can change a native protein conformation and impair the protein activity. The PSS/PEI/COX, PSS/PEI/COX/PEI/CE, PSS/PEI/COX-CE/PEI etc. layered structures were prepared on the surface of a platinum electrode, ITO coated glass plate, quartz crystal microbalance, quartz plates, mica and silicon substrates. Optical and gravimetric measurements based on an ultraviolet-visible absorption spectroscopy and a quartz crystal microbalance revealed that the enzyme multilayers thus prepared consist of molecular layered of the proteins. The surface morphology of such bilayer films was investigated by using atomic force microscopy. The electrochemical redox processes of the enzyme-layered films deposited either on platinum or ITO coated glass plate were investigated. The response current of cholesterol oxidase electrode with concentration of cholesterol was investigated at length.

Vapor-Phase Fuming Sulfuric Acid-Doped Poly(p-phenylene vinylene) as a Potential Humidity Sensor

Vapor-phase doping of poly(p-phenylene vinylene) (PPV) with fuming sulfuric acid has been investigated using the quartz crystal microbalance. Thin films of PPV were obtained on quartz crystal substrates by spin casting a precursor polymer, which is thermally converted to give the PPV product. Dopant mass uptake and the resistance of the film were recorded in situ during doping. A decrease in the resistance and therefore an increase in the conductivity of the film from the insulating to the metallic regime was observed. Mass uptake information was used to determine the dopant concentration at the maximum conductivity, the doping rate, and the diffusion coefficient of the polymer. The dopant concentration results were verified by Rutherford backscattering spectrometry and elemental analysis. The observation that the doped material tends to lose its metallic properties upon exposure to moisture in the atmospheric air has been used to investigate its potential as a humidity-sensing device. The golden metallic appearance of the film changes as well. The conductivity can be returned by application of a dynamic vacuum. Fuming sulfuric acid-doped films were exposed to a range of relative humidities, from 4 to 75%. A rapid and significant linear response (over four orders of magnitude) to all percent humidities was observed. Fuming sulfuric acid-doped PPV may have the potential for applications as a humidity sensor or as a disposable shut-off switch in moisture-sensitive devices. © 2001 The Electrochemical Society. All rights reserved.