Yazar "Acar, Selim" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • Küçük Resim
    Öğe
    Effect of Cd dopant on structural, optical and CO2 gas sensing properties of ZnO thin film sensors fabricated by chemical bath deposition method
    (Springer Science and Business Media Deutschland GmbH, 2021) Altun, Büşra; Karaduman Er, Irmak; Çağırtekin, Ali Orkun; Ajjaq, Ahmad; Sarf, Fatma; Acar, Selim
    Cadmium-doped zinc oxide (Cd-doped ZnO) films were produced by economic facile chemical bath deposition method. The Cd doping content was adjusted as 1%, 3%, 5% and 7%. The structural, morphological and optical properties of the films were characterized by XRD, Raman, SEM and UV–Vis. The response in a carbon dioxide atmosphere was measured by varying the concentration up to 100 ppm at different working temperatures (30–250 °C). XRD measurements demonstrated that all synthesized films have a good crystallite structure with hexagonal wurtzite dominant phase. A large variety of nanostructures are randomly distributed over the films’ surfaces depending on Cd doping content as was manifested by the corresponding SEM images. From the transmittance analysis, an ultraviolet absorption edge corresponding to pure ZnO film undergoes a redshift with the increase in Cd content. The results from Raman spectra are in good agreement with the XRD results. From the gas sensing measurements, a high response toward 100 ppm CO2 gas was detected by 3% Cd-doped ZnO sensor (88.24% at 125 °C) with an acceptable response of 8.36% at room temperature, which exhibited the lowest response/recovery times as well as highest selectivity, stability and reproducibility. Changes in the CO2 gas sensing response as a function of Cd doping content are explained based on particle size, optical bandgap and surface images.
  • [ X ]
    Öğe
    Influence of Different Aluminum Sources on the NH3 Gas-Sensing Properties of ZnO Thin Films
    (Springer, 2018) Ozutok, Fatma; Karaduman, Irmak; Demiri, Sani; Acar, Selim
    Herein we report Al-doped ZnO films (AZO) deposited on the ZnO seed layer by chemical bath deposition method. Al powder, Al oxide and Al chloride were used as sources for the deposition process and investigated for their different effects on the NH3 gas-sensing performance. The morphological and microstructural properties were investigated by employing x-ray powder diffraction, scanning electron microscopy analysis and energy-dispersive x-ray spectroscopy. The characterization studies showed that the AZO thin films are crystalline and exhibit a hexagonal wurtzite structure. Ammonia (NH3) gas-sensing measurements of AZO films were performed at different concentration levels and different operation temperatures from 50 degrees C to 210 degrees C. The sample based on powder-Al source showed a higher response, selectivity and short response/recovery time than the remaining samples. The powder Al sample exhibited 33% response to 10-ppm ammonia gas at 190 degrees C, confirming a strong dependence on the dopant source type.
  • Küçük Resim
    Öğe
    Influence of isovalent Cd doping concentration and temperature on electric and dielectric properties of ZnO films
    (Elsevier Ltd, 2021) Altun, Büşra; Ajjaq, Ahmad; Çağırtekin, Ali Orkun; Karaduman Er, Irmak; Sarf, Fatma; Acar, Selim
    In this study, pure zinc oxide and lightly cadmium doped zinc oxide (Zn1-xCdxO; x = 0.01, 0.03, 0.05 and 0.07) films were synthesized by chemical bath deposition to mainly investigate the possible impact of isovalent (in particular Cd) doping ratio and temperature on their electric and dielectric features. X-ray diffraction patterns revealed that all produced films have a dominance of ZnO hexagonal wurtzite structure with the emergence of a minor CdO cubic phase at x ≥ 0.03, and predicted the decrease in average crystallite sizes with Cd doping. Cd content in the films was verified by energy dispersive X-ray analysis. Images of scanning electron microscopy revealed the formation of nanorods and spheres on the surface of pure ZnO film which changed to porous/agglomerative spheres with Cd doping. Then a comprehensive electric and dielectric analysis was carried out as a function of frequency in a wide temperature range (300–700 K) using two separate experimental data sets, (Z, θ) and (C, G). The results demonstrated the critical effect of temperature and Cd doping ratio on the electrical and dielectric properties of ZnO films. Among the investigated films, Zn0·97Cd0·03O film recorded highest conductivity and enhanced dielectric properties which was attributed to the equal activation of grains and grain boundaries in the film structure verified by the estimation of activation energies from impedance spectrum. However, the effect of Cd doping on electric and dielectric properties was prominent only below 500 K, beyond which the doping effect became negligible which might be correlated with the effective dominance of grain boundaries at high temperatures as was witnessed by modulus spectrum.
  • Küçük Resim
    Öğe
    Substrate critical effect on the structural and H-2 Gas sensing characteristics of solution-processed Zn0.075Cu0.025O films
    (IOP Publishing, 2021) Sarf, Fatma; Er, Irmak Karaduman; Yakar, Emin; Acar, Selim; Yakar, Emin
    In this study, we report the synthesis of Zn0.075Cu0.025O films by chemical bath deposition to determine the effect of substrate (glass slide or ZnO seed layer) on the structural and H2 gas sensing properties of the produced films. The crystal phase, structural topography, surface morphology, and functional groups of the as-synthesized films as well as H2 gas sensing properties were investigated. Although both films have a hexagonal wurtzite structure, ZnO seed layer-based Zn0.075Cu0.025O film is more crystalline than glass slide-based Zn0.075Cu0.025O films. ZnO seed layer-based Zn0.075Cu0.025O films exhibited much more nanorod and fewer nanosphere forms compared to glass slide-based Zn0.075Cu0.025O films. EDX analysis and Raman spectra of both samples confirmed the presence of defects in Cu: ZnO samples. ZnO seed layer-based sensors showed higher response (140%) and lower operating temperature (80 °C) compared to glass slide-based sensors(87% response and 140 °C operating temperature). The most important thing to note here is that the fabricated sensors exhibited a high response at room temperature. The responses at room temperature were found as 46% and 23% for the ZnO seed layer-based and glass slide-based sensors, respectively. Sensors operating at room temperature are especially important for commercial applications.
  • [ X ]
    Öğe
    The role of rare-earth metal (Y, Ru and Cs)-doped ZnO thin films in NH3 gas sensing performances at room temperature
    (Springer, 2020) Sarf, Fatma; Er, Irmak Karaduman; Yakar, Emin; Acar, Selim
    Pure and rare-earth metal [Yttrium (Y), Ruthenium (Ru) and Caesium (Cs)]-doped ZnO thin films were deposited onto In-doped SnO2 substrates by chemical bath deposition. The present study detailed investigated the effect of rare-earth metal-doped ZnO on NH3 gas sensing. X-ray diffraction analysis indicated that the incorporated rare-earth metal ions substitute Zn sites in the ZnO lattice. Dimension of ZnO films decreased with rare-earth metal doping which detected from surface morphology images. The response of 100 ppb NH3 gas was calculated to be 0.80 (200 degrees C), 14.00 (90 degrees C), 17.00 (50 degrees C), and 10.00 (120 degrees C) for the pure, Y-, Ru-, and Cs-doped ZnO films, respectively. In addition, the response of 15 ppm NH3 gas at room temperature was calculated to be 0.20, 27.00, 57.00, and 18.00 for undoped Y-, Ru-, and Cs-doped ZnO films, respectively.
  • [ X ]
    Öğe
    Varying electrical and dielectric properties of Ni:SnO2 films by MWCNTs and GNPs coating
    (Iop Publishing Ltd, 2022) Sarf, Fatma; Er, Irmak Karaduman; Ajjaq, Ahmad; Cagirtekin, Ali Orkun; Yakar, Emin; Acar, Selim
    In this research, pure SnO2 and Ni-doped SnO2 (Ni:SnO2) nanocomposite films were produced by chemical bath deposition method and the latter were coated with multi-walled carbon nanotubes (Ni:SnO2/MWCNTs) or graphene nanoplatelets (Ni:SnO2/GNPs) by spin coating. All samples have tetragonal rutile SnO2 structure with the presence of carbon (002) peak in MWCNTs- or GNPs-coated films. Crystallite size of SnO2 films decreased remarkably with Ni doping followed by a slight decrease with MWCNTs coating and slight increase with GNPs coating. Scanning electron microscope images manifested a dispersed agglomerative nature of SnO2 nanoparticles which reduced especially with MWCNTs coating due to the porous surface provided by carbon nanotubes. From the photoluminescence measurements, oxygen defects-related peaks were spotted in the SnO2-based structures with different luminescence intensities. The most significant decrease in resistance was observed with the addition of GNPs into Ni-doped SnO2 nanocomposites compared to the other produced films mainly due to the synergetic effect that promotes excellent charge transfer between surfaces of Ni:SnO2 and graphene nanosheet. The huge increase in conductivity of GNPs-coated films led to a huge increase in dielectric losses and this followed by a drop down of dielectric constant of the GNPs-coated films.