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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, SelimCadmium-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.Öğe Enhancing the Co gas sensing properties of ZnO thin films with the decoration of MWCNTs(Springer, 2019) Özütok, Fatma; Karaduman Er, Irmak; Acar, S.; Demiri, S.Multi-walled carbon nanotubes (MWCNTs) onto flower-like patterned ZnO seed layers were prepared by spin coating method. The etching of the MWCNTs was examined by HCl acid treatment. The effect of structural, morphological and elemental properties of the ZnO/MWCNTs were determined by XRD, SEM, and EDX, respectively. The gas sensing properties of ZnO seed layer and MWCNT/ZnO nanocomposites were studied as a function of operating temperature and gas concentration. The incorporation of MWCNT were given results such as reducing the operating temperature to 70 degrees C and enhancement in sensor response for 25ppm CO gas. It was obtained that the highest sensing response of 62% at 70 degrees C for raw-MWCNTs/ZnO sensor as compared to etched-MWCNT/ZnO and ZnO sensor which gave a sensing response of 19% and 21% at operating temperature of 70 degrees C and 150 degrees C, respectively. Results showed that the deposition of metal oxide sensors with MWCNT is a promising strategy for improvement of CO gas sensing properties.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, SelimIn 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.Öğe Optical and Electrical Characterization of Crystallized M:WO3 (Cu, Fe, Ni) Films in Acidic Medium(Çanakkale Onsekiz Mart Üniversitesi, 2024) Yakar, Emin; Karaduman Er, Irmak; Sarf, FatmaPure and metal (M) doped [copper (Cu), nickel (Ni) and iron (Fe)] WO3 films have been produced on In:SnO2 (ITO) slides by using facile chemical bath deposition and then annealed at 500 oC for 2 h. Structural, morphological, electrical and optical properties of the produced WO3-based films were examined. Monoclinic WO3 phase were observed in all the samples, and the peak intensities were decreased by metal inclusion with heterogeneous film growth on ITO substrate. Slight shifts from defect related emission peaks (blue and green) were observed in metal-substituted WO3 samples from PL study. An optical band gap was observed to decrease in M:WO3 samples. The surface resistance values were significantly reduced by metal additives compared to its pure counterpart, especially by the inclusion of nickel ions in WO3. The results indicated that nucleus growth and thereby impurity/defect-related surfaces had a serious effect on the optical and electrical properties of M:WO3 films.
