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    Flexible nanostructured CuO thin film: A promising candidate for wearable real-time sweat rate monitoring devices
    (Elsevier Science Sa, 2022) Sahin, Buenyamin
    Hydration level monitoring ensures clinically convenient instructions for preventive medicine and disease diagnostics. This paper aims to develop a wearable metal-oxide based sensor for monitoring hydration levels using flexible nanostructured copper oxide (CuO) thin film. Nanostructured CuO thin films were designed and fabricated on flexible cellulose acetate (CA) substrates via the successive ionic layer adsorption and reaction (SILAR) method. The obtained CuO films vigorously adhered to the CA substrate, and the resulting coated substrates were efficiently flexible to be used as wearable hydration level monitoring systems to realize big data collection of human health. The sensing response of the CuO-based flexible sensors is heavily improved by optimizing the growth process.
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    Growth and characterization of Fe-doped CuO/ZnO binary oxide thin films for possible optoelectronic applications
    (Elsevier, 2024) Sogan, Serra; Yucel, Ersin; Sarikaya, Ebru Karakas; Kahveci, Osman; Aydin, Rasit; Akkaya, Abdullah; Sahin, Buenyamin
    Nanoscale binary oxide thin film structures of pristine and Fe-substituted CuO/ZnO have been produced on sodalime glass substrates by the SILAR method and characterized by different acceptable analytical approaches. The more irregular and lumpy ZnO in the pristine CuO/ZnO binary thin film sample evolved into more regular and hexagonal prismatic structures with the addition of Fe. XRD patterns of the samples indicated that both monoclinic CuO and hexagonal ZnO phases were present without any impurities. Optical analyses by meaning absorbance and transmittance measurements exhibit an important change in the energy band gap and transmittance value with the Fe doping ratio. The energy band edges of the bare sample shift to red with increasing Fe percentage in the starting solution, presumably due to an increase in the carrier concentration. The transfer length method (TLM) is used to define the conductivity properties of the samples, which considers the contact properties and structural features of thin films. The minimum specific contact resistivity of 0.865 x 10 6 Omega square was obtained by 3.0 % Fe-implemented CuO/ZnO binary oxide samples, and the addition of Fe increased the effective transfer length of thin films.
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    Syntheses, structural evolution, electrical and optoelectronic characterization of ZnO/CuO composite films doped with transition metal Mn2+ ions
    (Elsevier Sci Ltd, 2022) Safdar, Hamza; Aydin, Rasit; Sahin, Buenyamin
    This study was done aiming to evaluate the influence of manganese (Mn) as a transition metal on the morphological, structural, optical, electrical, and optoelectronic characteristics of nanostructured ZnO/CuO films. Different Mn concentrations (1 and 2 M%) were used to analyze these properties. In the present research, we have described the synthesis of nanocomposite pristine ZnO/CuO and Mn-doped ZnO/CuO (Mn: ZnO/CuO) oxide films by using simple successive ionic layer adsorption and reaction (SILAR) procedure. Scanning electron microscopy (SEM) and atomic force microscope (AFM) pictures reveal that the surface structure of ZnO/CuO nanocomposites was effectively altered by Mn2+ ion substitution. Energy-dispersive X-ray analysis (EDX) con-firms the presence of Zn, Cu, O, and Mn elements in the synthesized nanofilms. The film thickness had decreased from 1.65 to 1.23 mu m as a function of increasing Mn2+ concentration. The X-ray diffraction (XRD) pattern revealed that the synthesized ZnO/CuO nanocomposite was polycrystalline and the crystallite size decreases from 40.16 to 34.14 nm with increasing Mn2+ ion concentrations. The optical bandgap energy was found using Tauc's graph and it varied from 2.37 to 2.56 eV. A maximum average transmittance (30%) was obtained for 2 M % Mn2+ concentration. Electrical measurement of the ZnO/CuO composite films shows sheet resistance (Rs) change between 1.01 and 0.41 (x108 omega/sq.) depending on temperature from 300 K to 400 K. The biggest figure of merit observed in this work was 4.69 x 10-8 omega- 1. The results have shown that Mn-doping has an important effect on the physical attributes of SILAR-deposited ZnO/CuO films.