Sensitive Thin Film Research Articles

Study of the electrical properties of the thin film (SnO2 )1-X(Bi2O3)X Preparation by Vacuum evaporation system

In this study, bismuth element was added to the weight ratio of (0,1,3,5)% to tin element using powdered technology method. The thin film of (SnO2)1-X(Bi2O3)X have been prepared with a vacuum evaporation system and oxidized him in oven with temperature at 350° C for 30 min. Results (I-V) Characters with temperature showed that the thin film had a negative thermal resistance factor, while the results showed that the resistance value of the thin film increased from 1KΩ at (0%) to 7.5 KΩ at (5%). The thin film 's sensitivity to heat has also improved significantly. The energy activation decreased from 0,08eV at the addition (0%) to 0,03 eV at the addition of (3%)while increased to 0.087 eV at the addition of (5%) .

Detection of Amines in Lamb Spoilage by Optical Waveguide Sensor Based on Bromophenol Blue-Silicon Composite Film

We herein report the development of a bromophenol blue(BPB)-silicone composite film/K+-exchange glass optical waveguide(OWG) sensor for the detection of amines produced during the spoilage of lamb. The optical and structural properties of the sensitive thin film were studied by ultraviolet -visible(UV-Vis) spectroscopy, and the light source of the OWG detecting system was selected. Gas sensing measurements showed that the sensor exhibited a good selectivity, high sensitivity, and short response-recovery time towards volatile amine gases in the 0.00117— 11.72 mg/g range. The as-prepared optical waveguide device was subsequently applied in the determination of gases (namely trimethylamine, dimethylamine, and ammonia) emitted from the lamb samples(5 g) stored at room temper ature( 25 °C) and in a refrigerator(5 °C) for 0—4 d, and the total volatile basic nitrogen(TVB-N) contents were detected by UV-Vis spectroscopy, and the results were compared with those obtained using our detector. It was found that the sensing element was capable of detecting mixed gases produced by the decomposition of lamb samples in a refrigerator for 0.5 h, where the TVB-N content was lower than 35 μg/g.

The response of (GeS2)x(Sb2S3)(1-x) thin films to illumination and annealing

Amorphous (GeS2)x(Sb2S3)(1-x) films where 0.29 < x < 0.94 were prepared by thermal evaporation from previously synthetized bulk glass. The response of virgin and annealed states of films to the slightly over-band gap illumination with respect to the shift of the optical band gap (Egopt) and the slope of the optical absorption edge (B1/2) was studied. The magnitude of photo-bleaching and photo-darkening varied with the molar fraction of GeS2 (x) (the average coordination number CN) while a maximum of photo-sensitivity was observed, with respect to the experimental error of chemical composition determination, at CN ≈ 2.6 (x ≈ 0.80). The spectral sensitivity of photo-darkening was studied for the annealed state of the most sensitive thin film.

Layer by layer deposition of alternate carbon nanotubes and Ni films for efficient multilayer thin film temperature gauges

This study reports a novel approach for growing multilayer thin films consisting of alternate layers of carbon nanotubes (CNT) and nickel on Si (1 0 0) substrates and justifies their use in thin film temperature sensors. A low pressure chemical vapor deposition system was employed for synthesizing CNT films, while Ni films were deposited by electrodeposition. Porous-Si was used as substrate to increase adhesion between the layers of the multilayer structure. The structure of the multilayer films and the quality of the CNT grown were analyzed using several characterization methods, including scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray auger electron spectroscopy and Raman spectroscopy. The electrical characteristics were investigated using a van der Pauw setup and the effect of the increasing number of CNT layers in the multilayer structure was studied. The sensitivity of the multilayer film was found to increase with increasing number of CNT layers, despite the decrease of the temperature coefficient of resistance. On the other hand, the initial resistance was found to increase. Results indicated that these multilayer structures are appropriate for fabricating highly sensitive thin film gauges that can detect lower heat fluxes with more accuracy.

Silk fibroin and ultra-long silver nanowire based transparent, flexible and conductive composite film and its Temperature-Dependent resistance

A transparent, conductive, smooth, and temperature sensitive thin films was fabricated and characterized in this paper. Silk fibroin could be processed into transparent thin films, which can act as ideal opto-electronic substrates. As pure silk fibroin film is nonconductive, ultra-long silver nanowires coating and platinum sputtering were used to strengthen its conductivity. Ultra-long nanowires were used to reduce the junctions between wires, and platinum was to improve the conductivity of the film. The new nanowire-metal-organic composite film possesses excellent conductivity and good transmittance. The composite films containing different silver nanowires exhibit conductivities of as low as 6.9 Ω/sq, and transmittance of 60–80% in the visible light range. The films also showed potentials in practical applications as their resistance is almost linearly temperature-dependent. It also can transfer power to electrical devices. The new composite films could be expected to function in wearable electronics or implantable devices and sensors.

Achieving sensitive and stable indium oxide thin films for gamma radiation monitoring

Indium oxide thin films of thickness 600 nm prepared by thermal evaporation in vacuum were annealed at different temperatures from 350 to 550 °C. The impact of the post-deposition thermal annealing on the structural evolution of the films, including the growth of grains, was investigated by XRD and SEM. The annealed films were also evaluated by X-ray photoelectron and photoluminescence spectroscopy. The gamma radiation dose dependences of the optical energy band gap for the as-deposited and annealed thin films were investigated using transmittance measurements. The band gap decreases with increase of dose for the as-deposited and thermally treated films up to certain level and then increases. Coplanar devices were fabricated using the as-deposited films and films annealed at different temperatures. After exposing them to different gamma radiation doses, DC conductivity measurements were carried out. The gamma radiation sensing property of the indium oxide thin films annealed at 400 °C exhibits the highest sensitivity in comparison to the as-deposited films and films annealed at other temperatures. The annealing at temperatures higher or lower than 400 °C causes an increase of electrical resistivity and decrease in sensitivity of the films. Also, the stability of the sensor devices was studied for about 8 months. The results showed that the sensors made of the as-deposited films were stable for about 2 months and lost about 52% of their sensitivity in about 8 months whereas the sensors made out of the films annealed at 400 °C were stable for about 4 months and lost about 26% of their sensitivity in about 8 months. This study presents a key idea of using the post-deposition thermal annealing to achieve highly sensitive and stable In2O3 film as gamma radiation sensor.

Highly UV sensitive polycrystalline zinc selenide thin film grown by chemical bath deposition technique

In this communication, we report a significantly high UV sensitivity of polycrystalline zinc selenide thin films prepared by chemical bath deposition technique. A three order of magnitude of photo current to dark current ratio is obtained for the as-deposited film under UV exposure. However, the photosensivity is found to decrease sharply upon open air isochronal annealing of the sample. The variation of the photocurrent to dark current ratio with annealing temperature is attributed to shrinking diameter of nano-wire like structures exhibited by the films, variation of the band gap energy and a decrease in the grain boundary charge density of the material which collectively enhance the free carrier concentration in the band leading to a substantial loss in the photosensitivity of annealed films compared to the as-deposited film.

List of abstracts

. Results obtained in the analysis of single layer and multilayered carbon stacks produced by PLD at low temperature will be presented. The mechanical properties of carbon single layers deposited at various laser pulse fluences, like hardness and elasticity, were determined by means of nano indentation measurements. It will be shown that a wide variety of mechanical properties can easily be adjusted by adapting the process parameters.

Sensitivity enhancement experimental demonstration using a low cutoff wavelength SMS modified structure coated with a pH sensitive film

The multimode interference (MMI) effect in a single mode-multimode-single mode (SMS) can be used for development of wavelength shift detection based sensors. In this work, the focus is centered on obtaining wavelength shifts with low cutoff single mode fibers, which allows exploring the wavelength range from 600 to 1000 nm, where optical sources and detectors are less expensive than at longer wavelengths. In addition, the application of a reduction in the fiber diameter of the SMS structure by means of HF etching, combined with the deposition of a thin-film, enables to enhance the sensitivity of the devices at the same time the objective mentioned before is achieved. In this sense, the effect of the deposition of a pH sensitive thin-film on SMS structures with different diameters allowed attaining a maximum sensitivity of 15 nm per pH unit in the range from pH 4 to pH 6, which improves by a factor of 3 the sensitivity of SMS sensors without etching operating at longer wavelengths.

A Comprehensive Study of a Micro-Channel Heat Sink Using Integrated Thin-Film Temperature Sensors.

A micro-channel heat sink is a promising cooling method for high power integrated circuits (IC). However, the understanding of such a micro-channel device is not sufficient, because the tools for studying it are very limited. The details inside the micro-channels are not readily available. In this letter, a micro-channel heat sink is comprehensively studied using the integrated temperature sensors. The highly sensitive thin film temperature sensors can accurately monitor the temperature change in the micro-channel in real time. The outstanding heat dissipation performance of the micro-channel heat sink is proven in terms of maximum temperature, cooling speed and heat resistance. The temperature profile along the micro-channel is extracted, and even small temperature perturbations can be detected. The heat source formed temperature peak shifts towards the flow direction with the increasing flow rate. However, the temperature non-uniformity is independent of flow rate, but solely dependent on the heating power. Specific designs for minimizing the temperature non-uniformity are necessary. In addition, the experimental results from the integrated temperature sensors match the simulation results well. This can be used to directly verify the modeling results, helping to build a convincing simulation model. The integrated sensor could be a powerful tool for studying the micro-channel based heat sink.

Metal-Organic Framework Thin Film Coated Optical Fiber Sensors: A Novel Waveguide-Based Chemical Sensing Platform.

Integration of optical fiber with sensitive thin films offers great potential for the realization of novel chemical sensing platforms. In this study, we present a simple design strategy and high performance of nanoporous metal-organic framework (MOF) based optical gas sensors, which enables detection of a wide range of concentrations of small molecules based upon extremely small differences in refractive indices as a function of analyte adsorption within the MOF framework. Thin and compact MOF films can be uniformly formed and tightly bound on the surface of etched optical fiber through a simple solution method which is critical for manufacturability of MOF-based sensor devices. The resulting sensors show high sensitivity/selectivity to CO2 gas relative to other small gases (H2, N2, O2, and CO) with rapid (<tens of seconds) response time and excellent reversibility, which can be well correlated to the physisorption of gases into a nanoporous MOF. We propose a refractive index based sensing mechanism for the MOF-integrated optical fiber platform which results in an amplification of inherent optical absorption present within the MOF-based sensing layer with increasing values of effective refractive index associated with adsorption of gases.

Design a sensitive optical thin film sensor based on incorporation of isonicotinohydrazide derivative in sol–gel matrix for determination of trace amounts of copper (II) in fruit juice: Effect of sonication time on immobilization approach

A new selective and sensitive optical sensor based on the incorporation of new synthesized N′-(2-hydroxy-5-iodobenzylidene) isonicotinohydrazide (HIBIN) as an effective reagent into the nanoporous of a transparent glass like material through the sol–gel process was developed which was suitable for the determination of copper (II) ions in aqueous solutions. The thin film sensors were constructed by spin-coating of prepared sol onto glass plate and their surface morphology were studied by field emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM) technique. Influence of sonication time on immobilization of HIBIN into silica matrix was investigated through calculation of leaching percentage. The Results shown that sonication time of 35 min is suitable to give more stable thin films without fluctuation in sensitivity and response time of presented sensor for a long period of time. The proposed optical sensor can be used for determination of copper (II) ions in the range of 9.1 × 10−8–1.12 × 10−5 mol L−1with a detection limit of 1.8 × 10−8 mol L−1. It also showed relative standard deviation 3.4 and 0.72% for reproducibility and repeatability respectively, along with a fast response time about of 2 min. The constructed optode is stable in wet conditions and could be stored for at least 6 weeks without observing any change in its sensitivity. The developed sensor was successfully applied to the determination of copper (II) in fruit juice and water samples which results were confirmed by atomic absorption spectrometry method.

Cryoconcentration of flavonoid extract for enhanced biophotovoltaics and pH sensitive thin films.

Flavonoids are important value added products for dye sensitized solar cells biosensors, functional foods, medicinal supplements, nanomaterial synthesis, and other applications. Brassica oleracea contains high levels of anthocyanins in leaf sap vacuoles, and there are many viable extraction techniques that vary in terms of simplicity, environmental impact, cost, and extract photochemical/electrochemical properties. The efficiency of value added biotechnologies from flavonoid is a function of anthocyanin activity/concentration and molecule stability (i.e., ability to retain molecular resonance under a wide range of conditions). In this paper, we show that block cryoconcentration and partial thawing of anthocyanin from B. oleracea is a green, facile, and highly efficient technique that does not require any special equipment or protocols for producing enhanced value added products. Cryoconcentration increased anthocyanin activity and total phenol content approximately 10 times compared with common extraction techniques. Cryoconcentrated extract had enhanced electrochemical properties (higher oxidation potential), improved chroma, and higher UV absorbance than extract produced with other methods for a pH range of 2-12, with minimal effect on the diffusion coefficient of the extract. As a proof of concept for energy harvesting and sensor applications, dye sensitized solar cells and pH-sensitive thin films were prepared and tested. These devices were comparable with other recently published biotechnologies in terms of efficacy, but did not require expensive/environmentally detrimental extraction or concentration methods. This low cost, biorenewable, and simple method can be used for development of a variety of value added products. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:206-217, 2018.

Synthesis of highly selective and sensitive Cu-doped ZnO thin film sensor for detection of H2S gas

Copper (Cu) doped zinc oxide (ZnO) thin films were successfully prepared by a simple sol-gel spin coating technique. The effect of Cu doping on the structural, morphology, compositional, microstructural, optical, electrical and H2S gas sensing properties of the films were investigated by using XRD, FESEM, EDS, FTIR, XPS, Raman, HRTEM, and UV–vis techniques. XRD analysis shows that the films are nanocrystalline zinc oxide with the hexagonal wurtzite structure and FESEM result shows a porous structured morphology. The gas response of Cu-doped ZnO thin films was measured by the variation in the electrical resistance of the film, in the absence and presence of H2S gas. The gas response in relation to operating temperature, Cu doping concentration, and the H2S gas concentration has been systematically investigated. The maximum H2S gas response was achieved for 3at% Cu-doped ZnO thin film for 50ppm gas concentration, at 250°C operating temperature.

Phase composition of gas sensitive thin films of tin oxide operating at near room temperature

We have studied the phase composition of thin polycrystalline tin oxide films deposited on silicon substrates by reactive RF magnetron sputtering. The films are sensitive to ethanol vapors at 38°C. They consist of SnO2 crystallites with the average grain size of about 7 nm, covered with a nanodimensional layer of amorphous SnO phase. It was found that the volume fraction of the former phase is about 95% and that of the latter phase is about 5%. Calculations of the film texture indicate the predominant growth of SnO2 crystals along 〈110〉, 〈211〉, and 〈310〉 crystal directions perpendicular to the substrate.

Fabrication of Chitosan-Polyethylene Oxide Polymeric Thin Film Using Electrochemical Deposition for Detection of Volatile Organic Compounds

This study focused on the fabrication of chitosan-polyethylene oxide sensitive thin film. The polyethylene oxide was used as an additive to enhance the electrical properties of chitosan towards ethanol and methanol gases. The chitosan-polyethylene oxide sensitive film was fabricated using electrochemical deposition technique to deposit a thin film of the sensitive blend on the printed circuit board surface. The sensitive blend electrical (I-V) properties were tested using a specific developed test chamber. Ethanol and methanol volatile organic compound gases were chosen in this work to study the thin sensing properties of the chitosan-polyethylene oxide film. The analyzed data demonstrated that chitosan-polyethylene oxide sensitive film was capable to detect the VOC gas molecules and showed that the sensitive blend was significantly selective to ethanol over methanol gas with output values of 0.31 µA and 0.023 µA respectively. Atomic force microscopy test was used to characterize the morphology and roughness of the pure chitosan and chitosan-polyethylene oxide sensitive films.

Morphology and inner structure of ethanol sensitive thin films of tin oxide operating at near room temperature

Thin tin oxide films were fabricated by reactive RF magnetron sputtering. It was shown that the films possess gas sensitivity to ethanol vapor at 38°C. Measurements of the morphology and cleavage inner structure of the samples by atomic-force and scanning electron microscopy demonstrate that the films are composed of nanodimensional rod-like grains oriented normally to the substrate. The grains are separated by pores piercing the whole film. It was found that the grain diameter distribution is normal logarithmic one with several centers related as small integers, which indicates that the grains coalesce. The minimum grain size of 6 nm might correspond to the critical nucleus size under the used conditions of film deposition.

Surface plasmon resonance refractive index sensor based on ultraviolet bleached polymer waveguide

In this paper, a compact refractive index (RI) sensor based on the resonant interaction between surface plasmon polaritons (SPP) mode and polymer waveguide mode is demonstrated. The hybrid plasmonic waveguide consists of ultraviolet (UV) sensitive SU-8 polymer and thin gold film on a silica layer. The SPP mode field is theoretically confirmed to be sensitive to the RI of analyte on the metal film surface. UV light bleaching method is adopted to fabricate the channel waveguide, which is covered by a 35 nm-thick gold layer. Microfluidic channel is used to flow organic solutions with RI of 1.52–1.60 through the sensing area. The experimental result indicates that the device has a sensitivity of 1023dB/RIU, corresponding to a resolution of 1×10−6 refractive index units (RIU) at 1550nm. The advantages of inherent feature and simple fabrication promise its potential for a portable, compact, and easily-produced refractometer.

Interferometrically stable, enclosed, spinning sample cell for spectroscopic experiments on air-sensitive samples.

In experiments with high photon flux, it is necessary to rapidly remove the sample from the beam and to delay re-excitation until the sample has returned to equilibrium. Rapid and complete sample exchange has been a challenge for air-sensitive samples and for vibration-sensitive experiments. Here, a compact spinning sample cell for air and moisture sensitive liquid and thin film samples is described. The principal parts of the cell are a copper gasket sealed enclosure, a 2.5 in. hard disk drive motor, and a reusable, chemically inert glass sandwich cell. The enclosure provides an oxygen and water free environment at the 1 ppm level, as demonstrated by multi-day tests with sodium benzophenone ketyl radical. Inside the enclosure, the glass sandwich cell spins at ≈70 Hz to generate tangential speeds of 7-12 m/s that enable complete sample exchange at 100 kHz repetition rates. The spinning cell is acoustically silent and compatible with a ±1 nm rms displacement stability interferometer. In order to enable the use of the spinning cell, we discuss centrifugation and how to prevent it, introduce the cycle-averaged resampling rate to characterize repetitive excitation, and develop a figure of merit for a long-lived photoproduct buildup.

基于表面温敏薄膜的锥形双包层光纤温度传感器

基于表面温敏薄膜的锥形双包层光纤温度传感器