Interdigitated Electrode Substrates Research Articles

Vertically aligned mesoporous Ce doped NiO nanowalls with multilevel gas channels for high-performance acetone gas sensors

In recent years, the potential use and development of acetone gas sensors in health monitoring and self-diagnostic applications has attracted increasing attention. Thus, accurate sensing of acetone is of crucial importance in the non-invasive diagnosis of diabetes. However, challenges remain in the detection of acetone, such as high concentrations detection limit, high operating temperature and slow response dynamics. Herein, vertically aligned Ce-doped mesoporous NiO nanowalls are prepared on Ag-Pd interdigitated electrode substrate using an in-situ growth method. The gas sensing performances show that the as-made 4 mol% Ce-doped NiO nanowalls has excellent gas response value (3.2) to 10 ppm acetone at a lower operating temperature (175 ℃) with fast adsorption and desorption equilibrium (13 s/7 s). Vertically aligned mesoporous NiO nanowalls doped by Ce element could pave the way for ultra-sensitive and low power consumption acetone gas sensors for breath gas detection.

Dual-Function Smart Windows Using Polymer Stabilized Cholesteric Liquid Crystal Driven with Interdigitated Electrodes.

In this study, we present an electrically switchable window that can dynamically transmit both visible light and infrared (IR) light. The window is based on polymer stabilized cholesteric liquid crystals (PSCLCs), which are placed between a top plate electrode substrate and a bottom interdigitated electrode substrate. By applying a vertical alternating current electric field between the top and bottom substrates, the transmittance of the entire visible light can be adjusted. The cholesteric liquid crystals (CLC) texture will switch to a scattering focal conic state. The corresponding transmittance decreases from 90% to less than 15% in the whole visible region. The reflection bandwidth in the IR region can be tuned by applying an in-plane interdigital direct current (DC) electric field. The non-uniform distribution of the in-plane electric field will lead to helix pitch distortion of the CLC, resulting in a broadband reflection. The IR reflection bandwidth can be dynamically adjusted from 158 to 478 nm. The electric field strength can be varied to regulate both the transmittance in the visible range and the IR reflection bandwidth. After removing the electric field, both features can be restored to their initial states. This appealing feature of the window enables on-demand indoor light and heat management, making it a promising addition to the current smart windows available. This technology has considerable potential for practical applications in green buildings and automobiles.

Investigation of conduction mechanism and UV light response of vertically grown ZnO nanorods on an interdigitated electrode substrate.

Vertically aligned zinc oxide nanorod (ZnO-NR) growth was achieved through a wet chemical route over a comb-shaped working area of an interdigitated Ag-Pd alloy signal electrode. Field-emission scanning electron microscopy images confirmed the formation of homogeneous ZnO-NRs grown uniformly over the working area. X-ray diffraction revealed single-phase formation of ZnO-NRs, further confirmed by energy-dispersive X-ray spectroscopy analysis. Temperature-dependent impedance and modulus formalisms showed semiconductor-type behavior of ZnO-NRs. Two electro-active regions i.e., grain and grain boundary, were investigated which have activation energy ∼0.11 eV and ∼0.17 eV, respectively. The conduction mechanism was investigated in both regions using temperature-dependent AC conductivity analysis. In the low-frequency dispersion region, the dominant conduction is due to small polarons, which is attributed to the grain boundary response. At the same time, the correlated barrier hopping mechanism is a possible conduction mechanism in the high dispersion region attributed to the bulk/grain response. Moreover, substantial photoconductivity under UV light illumination was achieved which can be attributed to the high surface-to-volume ratio of zinc oxide nanorods as they provide high density of trap states which causes an increase in the carrier injection and movement leading to persistent photoconductivity. This photoconductivity was also facilitated by the frequency sweep applied to the sample which suggests the investigated ZnO nanorods based IDE devices can be useful for the application of efficient UV detectors. Experimental values of field lowering coefficient (βexp) matched well with the theoretical value of βS which suggests that the possible operating conduction mechanism in ZnO nanorods is Schottky type. I-V characteristics showed that the significantly high photoconductivity of ZnO-NRs as a result of UV light illumination is owing to the increase in number of free charge carriers as a result of generation of electron-hole pairs by absorption of UV light photons.

Resistive type NO2 gas sensing in polymer-dispersed liquid crystals with functionalized-carbon nanotubes dopant at room temperature

The embedding of liquid crystal (LC) droplets into polymer matrices yields polymer-dispersed liquid crystals (PDLCs), which play an important role in the formation of mechanically resistant films for flexible photonic devices. Despite the fact that PDLCs respond to a variety of physical and chemical stimuli, LCs have had limited success in detecting environmental pollutants due to a lack of reactive functional groups in their structures. In this work, we execute the idea of integrating functionalized carbon nanotubes (f-CNTs) into PDLCs to accelerate the absorption of gas molecules at room temperature (RT). The proposed f-CNT-PDLC sensor device was prepared by depositing the composite mixture onto an interdigitated electrode substrate and carrying out phase separation under UV light exposure. Compared to the pure PDLC device, the proposed device exhibited a response of ~12.9 % and 1 % for 100 and 5 ppm of NO 2 gas, and a linear relationship was obtained with gas concentrations. Furthermore, this device displayed a good reproducibility over five cycles, exhibiting an excellent selectivity against other interfering gases, such as H 2 S, CO, H 2 , and NH 3 . The boosted response was attributed to charge transport between the NO 2 gas molecules and the f-CNTs, which was detected by measuring the change in electrical resistance caused by the f-CNTs, in addition to the orientational phase modulation of the f-CNTs and the LCs within a droplet. Our experimental results revealed that the proposed f-CNT-doped PDLCs are promising candidates for sensing various physical and chemical stimuli. • An f-CNT-doped PDLC sensor device was developed for NO 2 gas detection. • The f-CNT dopant significantly improved the sensing performance of the PDLC device. • A difference in the droplet configuration was identified with NO 2 gas molecules. • A fast and specific sensing response was achieved with proposed f-CNT-PDLC sensor.

An Investigation of the Ammonia-Sensing Mechanism of α-MoO3-Based Chemi-Resistive Sensors

Chemi-resistive ammonia sensors based on alpha-phase molybdenum trioxide (α-MoO3) are a simple and selective technology for measuring the concentration of gaseous ammonia for applications such as human breath sensing and monitoring selective catalytic reduction (SCR) systems [1-7]. The basic operating principle of these sensors is the correlation between the electrical resistance of the sensor and the concentration of ammonia to which the sensor is exposed. Typically, the sensor consists of an interdigitated electrode substrate covered with the α-MoO3 film [1-7]. The electrical resistance of the α-MoO3 film changes as a function of ammonia concentration. This change in resistance of the α-MoO3 film is commonly attributed to the alteration of the charge depletion layer (Λ) of the α-MoO3 particles through the reaction of ammonia with adsorbed oxygen species [5-9]. For α-MoO3, the charge depletion layer model predicts that the resistance of the film should decrease with increasing ammonia concentration. In addition to the charge depletion layer model, other sensing mechanisms have been suggested, such as the partial reduction by ammonia of the surface of the α-MoO3 film [1,2] and the formation of oxygen vacancies in the α-MoO3 lattice [3].The α-MoO3 film can be fabricated by a variety of methods, including sol-gel synthesis, ion beam deposition, hydrothermal synthesis, and flame spray pyrolysis [1-6]. In this work, the α-MoO3 film is fabricated using Reactive Spray Deposition Technology (RSDT) followed by annealing to develop crystallinity. The RSDT is a flame-based process that can be used for the fabrication of α-MoO3 films at a commercial scale. The initial development of ammonia sensors with RSDT-fabricated α-MoO3 films of varying morphology was presented at the 236th ECS Meeting as an oral presentation, “Ammonia-Sensing Properties of α-MoO3 Fabricated by Reactive Spray Deposition Technology (RSDT).” From these initial sensors, the sensor with the strongest response to ammonia was selected for further testing at concentrations between 0.1 ppm and 5 ppm ammonia in dry air at 400°C. These sensing results and the materials characterization of the sensor by SEM and XRD before and after 80 hours of continuous testing are reported in Ebaugh et al. [7] and are shown in Figures 1-3. In Figure 1, the sensing results among the three test cycles comprising the 80 hours of testing are quite repeatable; however, the results consistently depart from the prediction of the charge depletion layer model between 3 ppm and 5 ppm.To better explain this unexpected sensing behavior, additional electrochemical testing and materials characterization is needed. Specifically, normal pulse voltammetry (NPV) can be used to provide data pertaining to the electronic path through the α-MoO3 film and the reaction and transport of chemical species adsorbed on the α-MoO3 film. TEM analysis of the α-MoO3 can show the nanoscale morphology of the sensing material. It is well established that the nanoscale morphology of the metal-oxide film impacts its sensing behavior [8-10]. XPS can also be used to investigate the possible reduction of the surface of the α-MoO3 particles and the formation of oxygen vacancies in the α-MoO3 lattice. Data from the materials characterization of the sensing film (XRD, SEM, TEM, and XPS) will be used in conjunction with sensing results and NPV data to develop an explanation for the sensor behavior observed in [7]. An understanding of the ammonia-sensing mechanism will help to guide the optimization of the RSDT-fabricated α-MoO3 film to improve the performance of the sensor for a wide range of applications.References A. K. Prasad, et al. Thin Solid Films. 436 2003 pp. 46-51.P. Gouma, et al. IEEE Sensors Journal. 10 (1) 2010 pp. 49-53.A. K. Prasad, et al. Sensors and Actuators B: Chemical. 93 2003 pp. 25-30.P Gouma, et al. Journal of Breath Research. 5 2011 p. 037110.A. T. Güntner, et al. Sensors and Actuators B: Chemical. 223 2016 pp. 266-273.D. Kwak, et al. ACS Applied Materials & Interfaces. 11 2019 pp. 10697-10706.T. A. Ebaugh, et al. ACS Applied Materials & Interfaces. Under review.C. S. Rout, et al. Nanotechnology. 18 2007 p. 205504.M. E. Franke, et al. Small. 2 (1) 2006 pp. 36-50.N. Barsan, et al. Fresenius Journal of Analytical Chemistry. 365 1999 pp. 287-304. Figure 1

Zinc Oxide Sensing Devices for Meat Spoilage Detection

Introduction In North America, over 20% of the initial production of meat is lost due to waste. Losses and waste in industrialized regions are highest at the end of the food supply chain due to high per capita meat consumption and large amounts of waste generated by retailers and consumers [1]. Smart materials and devices can reduce this waste by detecting meat spoilage in the early stages. When meat proteins begin to degrade, they release biogenic amines (e.g. putrescine, NH2(CH2)4NH2). Detection of these amines can lead to an early indication of meat spoilage [2-4]. Gas sensing semiconductors such as ZnO can be used for this detection by measuring a change in electrical resistance due to charge transfer caused by the amine molecule on the surface. In this work, a chemiresistive response to amines is tested for by utilizing model test gases, including methylamine (NH2CH3) and dimethylamine (NH(CH3)2), with novel, synthesized ZnO nanomaterials optimized for this application. Sensor Fabrication and Testing ZnO nanostructures are synthesized directly onto interdigitated electrode substrates via a two-step hydrothermal process. ZnO nanomaterial deposition on the substrate surface is first seeded from solution, followed by nanostructure growth from a second solution at elevated temperatures. The morphology of the ZnO nanostructure deposits is controlled by adjusting the pH of the growth solution and by adjusting the point at which the seeded substrates are immersed into the growth solution. Different metal catalyst nanoparticles are deposited onto the ZnO via a wet chemical method to optimize the device response to amines and lower the operating temperature [5]. The ZnO nanostructures are characterized by SEM, TEM, and XPS (Figure 1).The sensor response to amines is tested using a home built apparatus. The amine test gas is diluted in air through mass flow controllers and then flowed over the device under test while the device resistance is monitored. The device temperature is set by a resistive heater and thermocouple located near the device and a closed loop controller. The entire apparatus is controlled by a central computer through a LabView script. Interference from moisture is tested for by flowing water saturated air over the device under test and monitoring for changes in resistance. Results and Conclusions A strong chemiresistive response to methylamine is found using the ZnO nanostructures, with a large increase in sensitivity occurring after decorating the nanostructures with Pd catalyst particles (Figure 1) [6]. The morphology of the ZnO nanostructure is optimized during synthesis as described above and is found to have a strong impact on the sensor response. The optimal response is found from a flower-like nanostructure morphology with a high surface area, large aspect ratios, and a percolated electrical network connectivity, as shown in Figure 1. Optimization of the morphology and the catalyst loading leads to a decrease in the operating temperature of the device and the observance of room temperature sensing. Experiments are underway to further characterize these responses and optimize the devices for high sensitivity, room temperature (or low temperature) operation. Interferences from moisture in the air would lead to issues with adoption of the technology and therefore tests are underway to check for such interferences. The ZnO materials have been successfully doped with Ga and Al, and experiments are planned to optimize the device response via this doping, as well as by UV exposure of the ZnO.

Improvement in NO2 Gas Sensing Performance Using Igzo Film Sensor

Nitrogen dioxide (NO2) and many other nitrogen oxides species (NOx) have an adverse health effect on human health. Exposure to these gases for a long time can alter the lung function as well as other respiratory conditions. Globally, it is estimated that 13% of children’s under 1-18 years have a new asthma related respiratory problem due to NO2 gas pollution [1]. Further, NO2 related health effect occurs where the concentration of NO2 are higher than 21 ppb according to WHO guidelines. Therefore, detection and monitoring of NO2 gas are very essential.In this study, Indium-Gallium-Zinc-Oxide (IGZO) films are grown using magnetron sputtering process for the detection NO2 gas. The IGZO films with a thickness of 50 nm were deposited on interdigitated electrode substrates in IGZO with 2:2:7 ratios sputtering target and annealed at 300 °C for 1 hr in O2 atmosphere. The sensor characteristics were studied at room temperature and higher working temperatures in NO2 environment with various concentrations. The sensor response (Rair/Rgas) of 1114 % was obtained for 100ppm NO2 concentration at 150 °C operating temperature as shown in Fig.1. Further to investigate the temperature effect on sensor properties, the sensor was annealed at 400 and 500 °C and also the selectivity of the sensor were examined with various gases.Reference : 1. P. Achakulwisut, M. Brauer, P. Hystad, S. C. Anenberg, Global, national, and urban burdens of paediatric asthma incidence attributable to ambient NO₂ pollution: estimates from global datasets, Lancet Planet Health 3, 166–78, (2019). Acknowledgment This research was supported by the MOTIE (Ministry of Trade, Industry & Energy (10048536) and the KSRC (Korea Semiconductor Research Consortium) support program for the development of future semiconductor devices. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning(NRF-2015M3A7B7045563). Figure 1

Proposal of a Sensing Mechanism of α-MoO3 Chemi-Resistive Sensors for Gaseous Ammonia in Air

Chemi-resistive ammonia sensors based on α-MoO3 are a simple and selective technology for measuring the concentration of gaseous ammonia [1-4]. Typically, the sensor consists of an interdigitated electrode substrate covered with the α-MoO3 film [2-4]. The measured electrical resistance of the α-MoO3 film on the substrate changes as a function of gaseous ammonia concentration to which the film is exposed. α-MoO3 is a n-type semiconductor [4], meaning that the electrical conductivity of α-MoO3 is dominated by free electrons as opposed to holes. The mechanism of ammonia sensing by n-type semiconducting metal oxides is commonly attributed to the alteration of the charge depletion layer (Λ) of the metal oxide particles through the reaction of ammonia with adsorbed oxygen species [4-10]. For n-type semiconducting metal oxides, the charge depletion layer model predicts that the resistance of the sensing film (α-MoO3) decreases with increasing concentration of reducing gas, such as ammonia, to which the sensor is exposed. In addition to the charge depletion layer model, other sensing mechanisms have been suggested, such as the partial reduction by ammonia of the surface of the MoO3 film and the formation of oxygen vacancies in the MoO3 lattice [1, 2, 11].It is generally understood that the sensitivity of the sensor can be tailored based on the particle size and morphology of the metal oxide film [5-10]. Therefore, as initial work, sensors with α-MoO3 films of varying morphology on gold-interdigitated electrodes with alumina substrate (DropSens P/N: IDEAU200) were fabricated by Reactive Spray Deposition Technology (RSDT) and tested for sensitivity to ammonia in synthetic air at 400ºC. This work was presented at the 236th ECS meeting as an oral presentation, “Ammonia-Sensing Properties of α-MoO3 Fabricated by Reactive Spray Deposition Technology (RSDT).” From these sensors, the sensor with the strongest response to ammonia was selected for further testing in ammonia and synthetic air at 400ºC with constant 1V DC bias across the sensor. This additional testing consisted of three 12-hour cycles, in which six ammonia concentrations were tested: 0.1, 0.3, 0.5, 1, 3, and 4.9ppm. Between each concentration, the sensor was flushed with synthetic air. Between each 12-hour cycle, the sensor was held at 400ºC in synthetic air for approximately 12 hours. For each ammonia concentration in each cycle, the sensing response (S) was calculated as S=Rgas/Rair where Rgas is the resistance of the sensor for a particular concentration of ammonia and Rair is the resistance of the sensor for the air flush immediately before the particular concentration of ammonia. Sensing results are shown in Figure 1. The results from cycle to cycle are quite repeatable; however, the results consistently depart from the prediction of the charge depletion layer model between 3ppm and 4.9ppm. In an attempt to assess whether these unexpected results could be attributed to morphological or crystallographic changes in the MoO3 film, SEM images and XRD plots were compared before and after the three 12-hour test cycles. SEM images were taken on both the gold and alumina portions of the electrode. Figures 2 and 3 show the SEM images and XRD plots, respectively. Neither SEM nor XRD results suggest that the unexpected sensing behavior may be attributed to morphological and/or crystallographic changes of the MoO3 film.To better explain the sensing behavior, additional testing, including electrochemical impedance spectroscopy (EIS) and X-Ray photoelectron spectroscopy (XPS), will be performed on the sensor. XPS has been reported to provide information regarding the partial reduction of the surface of the MoO3 film [1]. EIS can be used to develop equivalent circuits that are representative of the sensor. It has been shown that different properties of the sensing film, such as grain size and particle contact, correspond to different equivalent circuits [12]. Therefore, EIS data at varying ammonia concentrations can help to develop an understanding of the film properties involved in the sensing mechanism. Results from EIS, XPS, SEM, and XRD, along with an understanding of the charge depletion layer model, will be used to propose a thorough ammonia sensing mechanism for α-MoO3.

Improvement in NO2 Gas Sensing Performance Using Igzo Film Sensor

In this study, Indium-Gallium-Zinc-Oxide (IGZO) films are grown using magnetron sputtering process for the detection NO2 gas. The IGZO films with a thickness of 50 nm were deposited on interdigitated electrode substrates using polycrystalline IGZO target (In2O3:Ga2O3:ZnO = 2:2:7 mol. %) target and annealed for 1 hr in O2 atmosphere at temperature 300, 400 and 500 °C respectively. The sensor characteristics were studied from room temperature to 250 °C working temperatures. The maximum sensor response (Rair/Rgas) of 33.6, 27.9, 11.3 and 5.53 were obtained for 100 ppm NO2 concentration at 250, 200, 150 and 100 °C operating temperature respectively for IGZO sample annealed at 300 °C. The selectivity of the sensor was examined with various gases.

Optical anisotropy in electroactively elongated single-walled carbon nanotubes agglomerates

A thin layer of single-walled carbon nanotubes (SWCNTs) exhibiting optical anisotropy is prepared by electroactively elongating SWCNT agglomerates. SWCNTs are doped into a reactive mesogen (RM) solution, and the composite solution is spin-coated on an interdigitated-electrode substrate. The spherical shaped SWCNT agglomerates observed in the solution of thin layers are electroactively elongated and aligned along the direction of the external electric field. After elongating the SWCNT agglomerates, the transparency of RM-SWCNT thin composite layers increases by about 14%. In addition, the elongated SWCNT agglomerates present significant optical anisotropy such that an incident light with a polarization direction parallel and perpendicular to the elongated direction of SWCNTs is absorbed and transmitted, respectively. The electroactively elongating strategy adopted to realize the optical anisotropy of SWCNT agglomerates suggests a new way to fabricate an optically anisotropic SWCNT thin layer.

Trianglamine hydrochloride crystals for a highly sensitive and selective humidity sensor

In this work, we present a highly sensitive and selective capacitive humidity sensor. Trianglamine hydrochloride is used as the sensing material, which is synthesized by a [3+3] cyclocondensation reaction between terpthaldehyde and 1R,2R-cyclohexanediamine followed by addition of hydrochloric acid and vapor diffusion of acetone. The crystalline trianglamine hydrochloride salts are dispersed in acetonitrile and then coated on interdigitated electrode substrates by drop casting. The sensor response is characterized for relative humidity (RH) ranging from 5% to 95%. The sensor has a nonlinear response, where the sensitivity increases with an increase in RH. The sensor demonstrates, on average, normalized sensitivities of 0.015 and 6.9 per percent of RH below and above 65% RH, respectively. In addition, the sensor is characterized for hysteresis, long-term stability, effect of temperature, and selectivity. The hysteresis of the sensor is a maximum of about 20% RH and is stable for over 25 days. Temperature analysis of the sensors shows that the sensitivity decreases with increase in temperature. The material is shown to be highly selective with respect to volatile organic compounds (VOCs) and toxic/corrosive gasses. Overall, trianglamine hydrochloride is a promising material for developing a highly sensitive and selective capacitive transduction-based humidity sensor.

A Comparative Study of Interdigitated Electrode and Quartz Crystal Microbalance Transduction Techniques for Metal⁻Organic Framework-Based Acetone Sensors.

We present a comparative study of two types of sensor with different transduction techniques but coated with the same sensing material to determine the effect of the transduction mechanism on the sensing performance of sensing a target analyte. For this purpose, interdigitated electrode (IDE)-based capacitors and quartz crystal microbalance (QCM)-based resonators were coated with a zeolitic–imidazolate framework (ZIF-8) metal–organic framework thin films as the sensing material and applied to the sensing of the volatile organic compound acetone. Cyclic immersion in methanolic precursor solutions technique was used for depositing the ZIF-8 thin films. The sensors were exposed to various acetone concentrations ranging from 5.3 to 26.5 vol % in N2 and characterized/compared for their sensitivity, hysteresis, long-term and short-term stability, selectivity, detection limit, and effect of temperature. Furthermore, the IDE substrates were used for resistive transduction and compared using capacitive transduction.

Atmospheric Pressure Plasma Polymerization Synthesis and Characterization of Polyaniline Films Doped with and without Iodine.

Although polymerized aniline (polyaniline, PANI) with and without iodine (I2) doping has already been extensively studied, little work has been done on the synthesis of PANI films using atmospheric pressure plasma (APP) deposition. Therefore, this study characterized pure and I2-doped PANI films synthesized using an advanced APP polymerization system. The I2 doping was conducted ex-situ and using an I2 chamber method following the APP deposition. The pure and I2-doped PANI films were structurally analyzed using field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS) studies. When increasing the I2 doping time, the plane and cross-sectional SEM images showed a decrease in the width and thickness of the PANI nanofibers, while the AFM results showed an increase in the roughness and grain size of the PANI films. Moreover, the FT-IR, XPS, and ToF-SIMS results showed an increase in the content of oxygen-containing functional groups and C=C double bonds, yet decrease in the C–N and C–H bonds when increasing the I2 doping time due to the reduction of hydrogen in the PANI films via the I2. To check the suitability of the conductive layer for polymer display applications, the resistance variations of the PANI films grown on the interdigitated electrode substrates were also examined according to the I2 doping time.

TOF-SIMS study on nano size conducting polymer prepared by simple atmospheric pressure plasma polymerization technique for display applications

ABSTRACTWe had previously reported on a surface analysis investigation of newly atmospheric pressure plasma (APP) polymerized conducting polymers films, both plasma-polymerized polyaniline and polypyrrole (pPPy). In this study, time of flight secondary ion mass spectrometry (ToF-SIMS) has been used to characterize nano size conducting polypyrrole films between the conventional and novel APP source under room temperature. Specific negative and positive ions from pPPy were effective in monitoring the change in the pPPy content at the surface of the composites. This ToF-SIMS analysis clearly demonstrates that novel APP polymerization source is effective in increasing the surface polymer content and thus confirms previously published X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS) data based on some necessary assumptions. To check the suitability of the conductive layer for the display application, the resistance variations of the pPPy grown on the interdigitated electrode substrates are examined by doping with iodine.

Tin oxide-based thin films prepared by pulsed laser deposition for gas sensing

Thin tin dioxide films were prepared by large-area pulsed laser deposition, a ceramic target in oxygen atmosphere was used. The layers were structured on interdigitated electrode substrates using a two-side trenched silicon shadow mask. The influence of the oxygen background pressure during deposition on the electrical and morphological properties was investigated using four-point probe measurements, scanning electron microscopy, X-ray diffraction, and X-ray photo spectroscopy investigations. Pd was introduced into the films by DC magnetron sputtering. It was found that the resistive response to CO is increased for the Pd-doped samples. Cross-sensitivity to the oxidizing gas NO2 was investigated and the sensor showed high signals for this gas at lower temperatures.

19.6L: Late‐News Paper: How to Fabricate Much Brighter AC Electroluminescent Lamps: Optimizing the Alignment of the Emitting ZnS:Cu Phosphor Particles to the AC Field

AbstractThe photoluminescence and electroluminescence of loose ZnS:Cu crystals scattered on an interdigitated electrode substrate have been studied under 366nm UV light excitation and or under an applied AC field. From the response of the ZnS:Cu crystals to the AC field and their movement in the field it is shown that a greater understanding of the factors affecting ACEL panel performance can be gained. The findings light the way to the fabrication of very bright panels and a suggestion can be made to the expected luminescence of optimised ACEL lamps

Co-planar bi-metallic interdigitated electrode substrate for spin-coated organic solar cells

A bulk heterojunction organic solar cell with co-planar interdigitated electrodes was fabricated and tested. The co-planar electrodes had a separation distance of 1–3 μm and were fabricated from aluminum and nickel on a heavily oxidized silicon wafer using photolithography. The device was prepared by spin-coating MEH-PPV:PCBB in a 1:3 wt ratio with a total donor:acceptor solution concentration of 2.44%. The device demonstrated a strong photovoltaic response under AM1.5 illumination of 80 mW/cm 2 with an open circuit voltage of 0.704 V. The co-planar electrode design offers advantages in terms of electrode material selection and reliability as well as simplified device fabrication.

Response time of nanostructured relative humidity sensors

Capacitive relative humidity (RH) sensors were fabricated by coating countersunk interdigitated electrode substrates with nanostructured TiO 2 films produced using glancing angle deposition. Areal capacitance increased from ∼ 1 nF cm −2 to ∼ 800 nF cm −2 as relative humidity was increased from ∼ 2 % RH and 95% RH. For films deposited at 81 ° and with a thickness below 4 μ m, response time was ( 162 ± 4 ) ms μ m −1. Response times increased from 64 ms to 1440 ms as film thickness increased from 280 nm to 8.5 μ m. The linear dependence of response time with film thickness indicates that device response time is dominated by surface adsorption. Response time decreased with increasing deposition angle, with a slope of ( − 15.2 ± 1.6 ) ms degree −1 for the adsorption data, and ( − 17.3 ± 2.5 ) ms degree −1 for the desorption data. The optimum operating range of the sensors depends on deposition angle, and can be tuned to different ranges to match application needs.

Gas sensitive Langmuir–Blodgett films based on erbium bis[octakis(octyloxy)phthalocyaninato] complex

A new kind of sandwich-like erbium bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] complex Er[Pc ∗] 2 ( Pc ∗= Pc (OC 8H 17) 8; R=OC 8H 17) is used as film-forming material. The behaviors of pure Er[Pc ∗] 2 monolayer and Er[Pc ∗] 2 and stearic acid-mixed monolayer on pure water and 10 −4 M Cd 2+ subphases are investigated. Langmuir–Blodgett (LB) films based on Er[Pc ∗] 2 were deposited onto quartz substrate and planar interdigitated electrode substrate, and the characteristic and gas-sensing property of LB films are studied. It is found that a mixture of 1:6 Er[Pc ∗] 2/cadmium stearate (CS) forms an excellent material for the fabrication of gas-sensing LB films, giving uniformly deposited multilayers by Y-type deposition, transfer ratio is close to 1. The sensitive property of Er[Pc ∗] 2/CS mixed LB films to nitrogen dioxide (NO 2) gas is monitored by the change of conductivity during gas exposure. Erbium bis[phthalocyaninato] complex-based LB films are very sensitive to the change of NO 2 gas. The response time of 11-layer LB film to 100 ppm NO 2 is 20 s at room temperature.