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Selective Laser Sintering (SLS) is a widely used additive manufacturing (AM) technique for creating 3D geometries by adding materials in layers. Although neat polymer is mainly used in powder forms...

Recently, semiconductive polymeric materials have attracted attention as an active layer for detecting ionizing radiation because of their excellent properties such as flexibility, easy production, solution processability and low-cost production. This paper presents X-ray detection properties of Poly(3-hexylthiophene) (P3HT):Phenyl C61 butyric acid methyl ester (PCBM) blend structure with different PCBM loading ratios. P3HT:PCBM mixing ratio was changed from 1:0 to 1:2. Top contact of the pure and blend structured device were produced by using a solution based graphite ink. Devices were constructed with vertical bulk resistive architecture within an ohmic electrode structure as ITO/PEDOT:PSS/P3HT:PCBM/Graphite configuration. Graphite electrode was coated on the active layer with the spray coating method. All devices exhibited ohmic current-voltage (I–V) characteristics. The blend structured devices exhibited stable saw-tooth type behaviour in photocurrent responses against the on and off states of X-rays. Saw-tooth type responses could be evaluated as major evidence for a potential usage of organic electronic device technology direct radiation detectors. Although the best sensitivity value to X-ray was obtained with the blend structure with equal ratio, it was observed that the rise and decay times were shortened with the increase in the amount of PCBM in the blend structure from. © 2022 CERN: A5.H1.F5-27; Türkiye Enerji, Nükleer ve Maden Araştırma Kurumu, TENMAK; Istanbul Üniversitesi-Cerrahpasa, IÜC: FBA-2021-35885 This study was supported by Turkish Energy, Nuclear and Mineral Research Agency . Project number:. 2020 TENMAK(CERN)A5.H1.F5-27 and Scientific Research Projects Coordination Unit of Istanbul University-Cerrahpasa . Project number:. FBA-2021-35885 .s

WOS: 000418617000010 In the present work, europium (Eu) has been used as a dopant element in titanium dioxide (TiO2) crystal structure to enhance the photovoltaic performance of the inverted type organic solar cells fabricated with TiO2 thin film as an electron transport layer. Poly(3-hexylthiophene): phenylC61-butyric acid methyl ester (P3HT: PCBM) blend has been used as an active layer and Eu: TiO2 thin films have been fabricated with different Eu concentrations as 0, 1, 5, 7 and 10% (w/w) by sol-gel method. Effect of Eu doping concentration on the photovoltaic performance of the inverted type solar cells has been investigated. Inverted type organic solar cells using Eu doped TiO2 thin films as electron transport layer has been fabricated as a structure of ITO/Eu:TiO2/P3HT: PCBM/Ag. Power conversion efficiency of the fabricated solar cells increased from 1.16% to 2.47% at 5% Eu doping concentration. Electron transport and hole blocking properties of the TiO2 inter layer has been improved by Eu doping. Ahi Evran UniversityAhi Evran University [MMF.A3.16.009] This research is supported by Ahi Evran University Grant no.: MMF.A3.16.009.

In this work, we present a method to increase the performance in solution processed organic field effect transistors (OFET) by using gel as dielectric and molecular doping to the active organic semiconductor. In order to compare the performance improvement, Poly (methylmethacrylate) (PMMA) and Poly (3-hexylthiophene-2,5diyl) P3HT material system were used as a reference. Propylene carbonate (PC) is introduced into PMMA to form the gel for using as gate dielectric. The mobility increases from 5.72 x 10(-3) to 0.26 cm(2) V s(-1) and operation voltage decreases from -60 to -0.8 with gel dielectric. Then, the molecular dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) is introduced into P3HT via co-solution. The mobility increases up to 1.1 cm(2) V s(-1) and the threshold voltage downs to -0.09 V with doping. The increase in performance is discussed in terms of better charge inducing by high dielectric properties of gel and trap filling due to the increased carrier density in active semiconductor by molecular doping.

In this work, we have demonstrated how the intrinsic properties of a conjugated polymer can influence the electro-optical characteristics of photo sensitive organic field - effect transistors (Photo-OFETs). Photo-OFETs fabricated with three batches of poly2-methoxy,5-(3',7'-dimethyl-octyloxy)-p-phenylene vinylene (MDMO-PPV) were investigated in the scope of our work. Photo-OFETs were fabricated with the polymers, than electrically and electro-optically characterized. It was observed that the channel current and the field-effect mobility increase with increasing polymer molecular weight. Interestingly, the electro-optical characteristics and photo switching properties of the transistors were found to depend on the polydispersity (PDI) of the polymer as well. These results are explained in terms of influences of chain packing, ordering and trap density on the FET switching properties and transistor parameters. Display Omitted Photo-OFETs fabricated with three batches of poly2-methoxy,5-(3',7'-dimethyl-octyloxy)-p-phenylene vinylene (MDMO-PPV)Photo-OFETs were fabricated with the polymers, than electrically and electro-optically characterizedIt was observed that the channel current and the field-effect mobility increase with increasing polymer molecular weightThe electro-optical characteristics and photo switching properties were found to depend on the polydispersity (PDI)

In this study, a new approach was introduced for Photo-OFETs as a multi-layer structure. Poly(3-hexylthiophene-2,5-diyl) regioregular (P3HT) and Copper(II) phthalocyanine (CuPc) thin films were used as two different active photo-absorber layers in the same device structure. Poly(methyl methacrylate) (PMMA) was used as a dielectric layer and all devices were fabricated with a top-gate bottom-contact configuration. In order to investigate the effect of the location of each layer on the Photoresponsive organic field-effect transistors (Photo-OFET) performance, five different devices in various structures were produced and analyzed. Surface properties of active layers have been investigated via Atomic Force Microscopy (AFM) and effects of surface roughness on device performance have been discussed. P3HT/CuPc/P3HT multi-layered structure exhibited the best performance in terms of photoresposivity(as 45 mA/W) and photosensitivity (~ 2 × 10 3 ). Photo-OFET based on a multi-layer structure demonstrated superior performance with wider absorbance spectrum region compared to conventional single component devices of P3HT or CuPc. The proposed multi-layer structure can be a model to improve the realization of high performance Photo-OFETs. © 2019 Elsevier B.V.

We investigated the impedance parameters of cobalt titanium (Co-Ti) multilayer thin films deposited on native oxidized Si (100) substrate under ultra-high vacuum (4 x 10(-8) mbar) by magnetron sputtering at room temperature. Electrical properties of Co/Ti/Co multilayer films were analyzed depending on the thickness of Ti spacer layer with the impedance spectroscopy as a function of frequency. Co/Ti multilayer films exhibited dielectric relaxation in both real and imaginary part of dielectric constants at the kilohertz frequency region and piezoelectric properties at the megahertz frequency region. We determined that the fabricated multilayer films have complex and super imposed type behavior when DC conductivity is used at lower frequency, resonance event and relaxation properties. (C) 2014 Elsevier Ltd. All rights reserved.

WOS: 000349827200059, In this work, dense arrays of pure and Pd doped zinc oxide (ZnO) nanorods (NRs) were fabricated by an electrochemical growth. Pure and Pd doped ZnO NRs were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and optic spectroscopy. Structural studies confirmed that pure and doped ZnO NRs present the hexagonal wurtzite crystal structures. The optical properties of pure and doped ZnO NRs were found to present redshift by increasing doping concentration. The diameters of the NRs increase with increasing Pd doping concentration under same condition. Compared with pure ZnO NRs, the Pd doped ZnO NRs presents improved optical properties in terms of bandgap energy from 3.24 eV to 1.97 eV. These bandgap values were obtained by optical absorption using a UV-Visible spectrophotometer. In addition, Pd doping concentration in ZnO affects the active species on the surface such as oxygen deficiencies and hydroxyls. The electrochemically growing mechanism is also discussed in detail in the scope of this work. (C) 2015 The Electrochemical Society. All rights reserved., TUBITAK [113F403, 113M935], The authors thank KUYTAM at Koc University and Dr. Baris Yagci for SEM measurements. This research is supported by TUBITAK grant no.: 113F403 and grant no.: 113M935.

In this study, the hydrogen (H2) sensing properties of vertically aligned zinc oxide (ZnO) nanorods were investigated depending on annealing, Pd coating, temperature and electrode structure. ZnO nanorods were fabricated by using hydrothermal method on a glass substrate and an indium tin oxide (ITO) coated glass substrate. In order to determine the effects of annealing on the H2 sensor performance, the nanorods were heated at 500 C in dry air. H2 sensing measurements were done in the temperature range of 25-200 C. It was found that, the sensor response of Pd coated ZnO nanorods were much higher than the un-coated nanorods due to the catalytic effect of Pd thin film. Moreover, the un-annealed samples showed better sensor response than the annealed samples due to the number of oxygen deficiency. In addition, the lateral electrode structure showed higher sensor response than the sandwich electrode structure. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 64. 111M261 This study was supported by Scientific and Technological Research Council of Turkey (TUBİTAK) entitled “Development of Automotive Gas Sensors Based on Nano-Metal-Oxide Semiconductor with increased Selectivity, Sensitivity and Stability” (Project Number: 111M261). The authors thank to Dr. Anıl Gunay-Demirkol for SEM measurements.

Graphene-based sensors are mostly studied in terms of their responses to inorganic gases such as various nitrogen oxides or ozone. In this work, chemically derived graphene (CDG) is assessed in terms of its gas sensing properties at room temperature for a selected set of volatile organic compounds (VOCs) representing different chemical classes. CDG was coated on gold interdigital electrodes on a glass substrate by drop casting. Structural and morphological analyses were realized by surface electron microscopy and energy-dispersive X-ray spectroscopy techniques. Among the nine test analytes, the highest sensor sensitivities were observed for chlorobenzene, tetrachloroethylene, and triethylamine. The results show that CDG sensors arc not only sensitive to rather reactive inorganic gases, but can also be used in the detection of a wide range of VOCs.

In this study, zinc oxide (ZnO) nanorods were fabricated by using hydrothermal method and resistive type nitrogen dioxide (NO 2 ) sensing properties of the nanorods were investigated depending on temperature, NO 2 concentration, electrode position and the dimension of the nanorods. To produce ZnO seed layer, zinc acetate solution was coated on a glass substrate by using spin-coater. ZnO nanorods were grown by changing concentration of solution at 90 °C for 3 h onto seed layer coated substrate. ZnO nanorods were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was observed that the diameters of ZnO nanorods were approximately 30 nm, 60 nm and 120 nm depending on solution concentration. For gas sensing measurements, interdigitated Au electrodes were coated on top or bottom of ZnO nanorods by using thermal evaporator. All samples were tested against to NO 2 in dry air ambient depending on concentration (100 ppb–1 ppm) in the temperature range of 25–200 °C. The highest sensor response was observed for ZnO nanorods that were 60 nm in diameter. The response and recovery times for all sensors decreased with increasing temperature and the sensors were fully recovered above temperature of 100 °C.

ZnO nanorods were synthesized directly on the mass sensitive transducer elements, namely the quartz crystal microbalance (QCM), by electrochemical deposition techniques. Besides, vanadium pentaoxide (V2O5) thin films were evaporated on the ZnO nanorods using a thermal evaporation system. The fabricated chemical gas sensors were exposed to different levels of various volatile organic compounds (VOCs). The VOCs sensing measurements were realized at room temperature. The application of an additional V2O5 layer on the ZnO nanorods was found to improve the sensing performance of the nanorods. The highest responses were obtained for the analyte DMMP and the DMMP sensitivities of the sensors are at least three times higher than the sensitivities for the other tested VOCs. ZnO nanorods are considered excellent sensing materials on the QCM allowing selective detection of DMMP and other analytes at room temperature. (c) 2017 The Electrochemical Society. All rights reserved.

In this study, the electrical and nitrogen dioxide (NO2) sensing properties of a series liquid-crystalline octakisalkylthiophthalocyanine (C6S)8PcM [M = 2H, Ni, Cu, Zn] thin film were investigated. The thin films were coated on to the Interdigital Transducer (IDT) with gold electrodes, using jet-spray technique in an inert ambient from a solution of phthalocyanines in chloroform. The electrical properties of liquid-crystalline phthalocyanines were studied within wide temperature range from 293 to 423 K under the high purity nitrogen (N2) flow and in the frequency range from 500 Hz to 1 MHz for ac electrical measurements. It was observed that the I–V curves of all phthalocyanines showed a significant hysteresis at low temperature and the maximum dc conductivity obtained for (C6S)8PcZn thin film. The ac conduction mechanism of all thin films could be explained with quantum-mechanical tunneling (QMT) model. The NO2 gas sensing measurements were done in the concentration range of 1–10 ppm at the temperatures of 100 °C and 150 °C. The maximum sensor response (%) was obtained as approximately 10,000 and the response time was observed to be a few seconds for (C6S)8PcH2 thin film at 150 °C.

Yttrium (Y) doped ZnO thin films with concentrations of 1 at.%, 5 at.% and 10 at.% Y concentrations were deposited on glass substrates by using sol–gel dip coating method. The electrical properties of the films were measured dependence on temperature to identify the dominant conduction mechanism. It was found that thermally activated band conduction was the dominant conduction mechanism at high temperatures whereas, in the low temperature region, the dependence of the dc conductivity on temperature followed Mott’s variable range hopping (VRH) model. The temperature dependence of both the ac conductivity and the frequency exponent are reasonably well interpreted by the correlated barrier hopping (CBH) model. The imaginary part of the impedance at different temperatures shows a relaxation peak and its position shifts to higher frequency with increasing temperature. This suggests a temperature-dependent relaxation. As an application, the NO2 sensing properties of the films were investigated at 200 Ci n the concentration ranges of 100 ppb–1 ppm. The response characteristics of Y-doped ZnO films have shown a high sensitivity to NO2 at this temperature and the highest sensor response were observed for 1 at.% Y-doped ZnO film.

ZnO thin films were fabricated using the spin coating method, ZnO nanowires by cathodically induced sol–gel deposition by the means of an anodic aluminum oxide (AAO) template, and ZnO nanorods with the hydrothermal technique. For thin film preparation, a clear, homogeneous and stable ZnO solution was prepared by the sol–gel method using zinc acetate (ZnAc) precursor which was then coated on a glass substrate with a spin coater. Vertically aligned ZnO nanowires which were approximately 65 nm in diameter and 10 μm in length were grown in an AAO template by applying a cathodic voltage in aqueous zinc nitrate solution at room temperature. For fabrication of the ZnO nanorods, the sol–gel ZnO solution was coated on glass substrate by spin coating as a seed layer. Then ZnO nanorods were grown in zinc nitrate and hexamthylenetetramine aqueous solution. The ZnO nanorods are approximately 30 nm in diameter and 500 nm in length. The ZnO thin film, ZnO nanowires and nanorods were characterized by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). The NO 2 gas sensing properties of ZnO thin films, nanowires and nanorods were investigated in a dark chamber at 200 °C in the concentration range of 100 ppb–10 ppm. It was found that the response times of both ZnO thin films and ZnO nanorods were approximately 30 s, and the sensor response was depended on shape and size of ZnO nanostructures and electrode configurations.

In this study, the hydrogen sensing properties of nanoporous Pd–Ag and Pd–Cu alloy films based on anodic aluminum oxide (AAO) templates were investigated at various temperatures (25–100 °C) and hydrogen with concentrations in the range between 250 and 5000 ppm in high purity nitrogen to determine the temperature–sensitivity relationship. A hexagonally shaped AAO template of approximately 50 nm in diameter and 10 μm in length was fabricated as a substrate for supporting a nanoporous Pd alloy film with an approximate thickness of 80 nm. The morphologies of the AAO template and the Pd alloy films were studied by scanning electron microscopy (SEM). The hydrogen sensing properties of the nanoporous Pd–Ag and Pd–Cu alloy films were measured using a transient resistance method. The sensor responses of the nanoporous Pd–Ag and Pd–Cu films on the AAO template were better than the traditional Pd–Ag and Pd–Cu thin film sensors; the sensitivities of the sensors were approximately 1.6% and 1.2%, respectively, for 1000 ppm H 2 , and the detection limit was 250 ppm at room temperature. The highest sensitivity was measured at room temperature for all alloy nanoporous sensors, and the sensitivity of the Pd–Ag nanoporous alloy was higher than that of the Pd–Cu nanoporous alloy.

MgxZn1-xO (x=0.01-0.3) nanoparticles were synthesized by the sol-gel technique using solutions of Mg and Zn based organometalic compounds. The electrical properties of Mg doped zinc oxide (ZnO) were studied within wide temperature range from 300 to 500 K under the N2 gas flow (flow rate: 20 sccm) and in the frequency range from 40 Hz to 1 MHz for ac electrical measurements. The dc conductivities and the activation energies were found to be in the range of 10-9-10-6 S/cm at the room temperature and 0.26-0.86 eV respectively depending on doping rate of these samples. The ac conductivity was well represented by the power law Aωs. The conduction mechanism for all doped ZnO could be related to correlated barrier hopping (CBH) model. The complex impedance plots (Nyquist plot) showed the data points lying on a single semicircle, implying the response originated from a single capacitive element corresponding to the nanoparticle grains. The crystal structures of the MgxZn1-xO nanoparticles were characterized using X-ray diffraction. The calculated average particle sizes values of Zn1-xMgxO samples are found between 29.72 and 22.43 nm using the Sherrer equation. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study, vertically oriented ZnO nanowires have been fabricated using an Anodized Aluminum Oxide (AAO) template by a cathodically induced sol–gel electrodeposition method at room temperature. For fabrication of the AAO template anodization of Al was carried out in 0.3 M H2C2O4 solution under a constant voltage of 40 V. Electrodeposition of ZnO nanowires in the AAO template was carried out in aqueous Zn(NO3)2 solution. AAO template and ZnO nanowires were characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). It was observed that the ZnO nanowires were approximately 70 nm in diameter and 10 μm in length with high aspect ratio. ZnO nanowires were fabricated in a relatively large area of about 5 cm2.

In this study, hydrogen sensing properties of nanoporous Pd films based on Anodic Aluminium Oxide (AAO) templates grown on a silicon substrate have been investigated at various temperatures (25–100°C) and hydrogen concentrations (100–1000 ppm) to determine the temperature-sensitivity relationship. For this purpose, a hexagonally shaped AAO template of approximately 50 nm in diameter and 700 nm in length with 80 nm interpore distances was fabricated using two-step anodization of an Al film deposited on an n-type (100) oriented oxidized Si substrate. Then, the nanoporous surface of the AAO template was used as a substrate for supporting a nanoporous Pd film of an approximately thickness of 60 nm. The morphologies of the AAO template and Pd film coated on the AAO template were studied mainly by Scanning Electron Microscopy (SEM). Hydrogen sensing properties of the nanoporous Pd film were measured using a resistance transient method. It was found that the sensor response of the nanoporous Pd films on the AAO template was better than the traditional Pd thin film sensors, the sensitivity of the sensor was approximately 1.8% for 1000 ppm H2, and the detection limit was lower than 100 ppm at room temperature. The highest sensitivity was measured at room temperature.

In this study, the effect of oxidizing gases, such as oxygen (0 2 ), nitrogen dioxide (NO 2 ), and ozone (0 3 ), on a liquid-crystalline copper octakisalkylthiophthalocyanine[(C 6 S) 8 PcC U ] thin film was investigated in the temperature range of 25-150°C. Starting from a chloroform solution of (C 6 S) 8 PcCu, a jet-spray technique in an inert ambient atmosphere was used to coat the thin film of the compound on to an Interdigital Transducer (IDT) with gold electrodes. The concentration ranges for N0 2 and 0 3 exposed to the (C 6 S) 8 PcCu thin film were 1-10 ppm and 50 ppb-50 ppm, respectively. The response time in N0 2 measurements was observed to be approximately 1 min at room temperature, and it decreased to a few seconds with increasing temperature. A good sensor response of 2000% ppm -1 was observed when the sensor was exposed to 1 ppm N0 2 at room temperature. The oxidizing gases were found to be desorbed by annealing the thin film.

In this study, thin anodic aluminum oxide (AAO) templates both on silicon substrates (AAO template/SiO2/Si) and Ti-coated silicon substrates (AAO template/Ti/SiO2/Si) were developed for design of magnetic, electronic and optoelectronic devices, chemical sensors and chip-scale lithium-ion rechargeable microbatteries. Two types of AAO template were prepared by using a two-step anodization procedure. The templates were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The obtained thin AAO templates were approximately 50 nm in diameter and 700 nm in length with 80-nm interpore distances in a relatively large area of 6 cm2. A barrier layer of the AAO templates was removed by a cathodic polarization method in KCl solution for several seconds. The current–time transient during removing the alumina barrier layer of the thin AAO template and the mechanism of electrochemical dissolution of the barrier layer are given in detail.

WOS: 000373612500026, In this work, palladium (Pd) thin films were prepared via RF sputtering method with various thicknesses (6 nm, 20 nm and 60 nm) on both a flexible substrate and a hard substrate. Hydrogen (H-2) sensing properties of Pd films on flexible substrate have been investigated depending on temperatures (25-100 degrees C) and H-2 concentrations (600 ppm - 10%). The effect of H-2 on structural properties of the films was also studied. The films were characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction. It is found that whole Pd films on hard substrate show permanent structural deformation after exposed to 10% H-2 for 30 min. But, this H-2 exposure does not causes any structural deformation for 6 nm Pd film on flexible substrate and 6 nm Pd film on flexible substrate shows reversible sensor response up to 10% H-2 concentration without any structural deformation. On the other hand, Pd film sensors that have the thicknesses 20 nm and 60 nm on flexible substrate are irreversible for higher H-2 concentration (>2%) with film deformation. The sensor response of 6 nm Pd film on flexible substrate increased with increasing H-2 concentration up 4% and then saturated. The sensitivity of the film decreased with increasing operation temperature. (C) 2016 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [114M853], This study was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with project number of 114M853.

WOS: 000363815800038, Pristine and various palladium (Pd) doped ZnO nanorods have been synthesized on the quartz crystal microbalance (QCM) for volatile organic compound (VOCs) sensors at room temperature. The doping concentrations were varied from 0 mol% to 2.5 mol% by using electrochemical deposition method. The diameters of the fabricated nanorods were in the range of 100-200nm, and were increased with Pd doping. The tested VOCs included alcohols (ethanol, methanol, isopropyl), ester (ethyl acetate), aromatic (toluene, xylene), ketone (acetone) and chloroform in the different concentrations. The results indicated that the sensitivity of the sensing materials was enhanced with the increasing Pd doping concentrations except for the acetone and chloroform. The undoped ZnO nanorod sensor showed higher sensor response against to acetone and chloroform while exposing high concentration of two analytes due to the absorbing/adsorbing mechanism. All undoped and Pd doped nanorods sensors showed the highest sensitivity to xylene. (C) 2015 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [113F403, 111M261]; COST Action EuNetAir - European Network on New Sensing Technologies for Air-Pollution Control and Environmental Sustainability [TD1105, STSM-TD1105-16434], This study was partly supported by The Scientific and Technological Research Council of Turkey (TUBITAK), Grant number (GN): 113F403, GN: 111M261 and by COST Action TD1105 EuNetAir - European Network on New Sensing Technologies for Air-Pollution Control and Environmental Sustainability - by a Short Term Scientific Mission Year-2 (STSM-TD1105-16434, from 03-03-2014 to 28-03-2014): "Functionalization of ZnO Nanorods With Metals and Metal oxides For Gas Sensing Applications".

WOS: 000339994900047, This study reports the fabrication method and sensing performance for novel 1D zinc oxide (ZnO) nanorods and nanotubes grown on nickel MEMS cantilevers. The fabrication of the nanostructures and the cantilevers are simple and low-cost using standard lithography, electrodeposition, and hydrothermal etching processes. 1D ZnO nanostructures increase the total sensitive area for biological and chemical sensor applications. We performed experiments with various VOCs with a real-time sensor system developed in our laboratory. While Ni microcantilevers produced no signal, ZnO nanostructure coated microcantilevers showed good sensitivity and repeatable changes. Furthermore, the nanotube coated microcantilevers showed more than 10 fold increase in sensitivity compared to the nanorod coated microcantilevers which can be explained to the fact that ZnO nanotubes have higher surface area and subsurface oxygen vacancies and these provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods. The tests are performed using dynamic mode of operation near resonant frequency using magnetic actuation and optical sensing. The phase stability and the limit of detection of ZnO nanotube coated microcantilevers exposed to diethylamine (DEA) were 0.02 degrees and lower than 10 ppm, respectively. ZnO nanostructure coated microcantilevers have good potential for VOC sensor applications especially for amine groups. (C) 2014 Elsevier B.V. All rights reserved., TUBITAK-BIDEB National Postdoctoral Research Fellowship Program; TUBITAK [111E184, 113F403], Necmettin Kilinc was supported by TUBITAK-BIDEB National Postdoctoral Research Fellowship Program. The authors thank KUY-TAM and Dr. Bans Yagci for SEM measurements. This research is supported by TUBITAK Grant no.: 111E184 and 113F403.

Thermally stimulated current (TSC), photoresponse and gas sensing properties of zinc oxide (ZnO) nanorods were investigated depending on heating rates, illumination and dark aging times with using sandwich type electrode system. Vertically aligned ZnO nanorods were grown on indium tin oxide (ITO) coated glass substrate by hydrothermal process. TSC measurements were performed at different heating rates under constant potential. Photoresponse and gas sensing properties were investigated in dry air ambient at 200 degrees C. For gas sensing measurements, ZnO nanorods were exposed to NO2 (100 ppb to 1 ppm) in dark and illuminated conditions and the resulting resistance transient was recorded. It was found from dark electrical measurements that the dependence of the dc conductivity on temperature followed Mott's variable range hopping (VRH) model. In addition, response time and recovery times of ZnO nanorods to NO2 gas decreased by exposing to white light. (C) 2014 Elsevier B. V. All rights reserved. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [111M261] This study was supported by Scientific and Technological Research Council of Turkey (TUBITAK) entitled "Development of Automotive Gas Sensors Based on Nano-Metal-Oxide Semiconductor with increased Selectivity, Sensitivity and Stability" (Project Number: 111M261).

In this study, hydrogen (H2) gas sensing properties of palladium (Pd) & platinum (Pt) thin films coated and uncoated vertically alinged zinc oxide (ZnO) nanorods were investigated at different temperatures. On the other hand, the effects of annealing in dry air to gas sensing properties of the nanorods were investigated. Vertically aligned ZnO nanorods were fabricated by using hydrothermal method on glass substrate, and then Pd and Pt thin films was coated on to ZnO nanorods by using thermal evaporating system. The thickness of Pd or Pt thin film was approximately 15 nm. H2 sensing measurements were done in the temperature range of 25 - 200°C. It was found that the sensor response of Pd coated ZnO nanorods were much higher than uncoated ZnO nanorods because of catalytic effect Pd thin film. Moreover, unannealed samples showed better sensor response than annealed samples due to the surface charge number. The sensor response of all samples increased with enhancing temperature., Ministry of Development of Turkey (DPT); Scientific and Technological Research Council of Turkey (TÜBİTAK)

A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm−2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially.

The multilayer thin films consisting of alternating stacks of ferromagnetic Permalloy (Py) and ultra thin non-magnetic (sub-nanometer) spacer (Cr) layers have been investigated by using ferromagnetic resonance (FMR) and dc magnetization measurement techniques. The non-magnetic spacer layer thickness changes from 0.5 A to 2.5 A by 0.5 A steps. Polycrystalline composite metallic films were grown on Si substrate by usual magnetron sputtering techniques at UHV conditions. The magnetic hysteresis curves were recorded by conventional dc magnetization. The ac and dc magnetic properties were investigated by using ferromagnetic resonance. FMR measurements were carried out for different directions of external dc magnetic field in order to search magnetic anisotropy. Two strong and well defined peaks (acoustic and optic mode) were observed in FMR spectrum as the magnetic field direction approaches to the film normal. Their positions and relative intensities helped to characterize coupling species. The magnetic param...