Browsing by Author "Ozmentes, Resit"

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Characterization of Cuo/N-si Heterojunction Solar Cells Produced by Thermal Evaporation
(Sciendo, 2018) Ozmentes, Resit; Temirci, Cabir; Ozkartal, Abdullah; Ejderha, Kadir; Yildirim, Nezir
Copper(II) oxide (CuO) in powder form was evaporated thermally on the front surface of an n-Si (1 0 0) single crystal using a vacuum coating unit. Structural investigation of the deposited CuO film was made using X- ray difraction (XRD) and energy dispersive X- ray analysis (EDX) techniques. It was determined from the obtained results that the copper oxide films exhibited single-phase CuO properties in a monoclinic crystal structure. Transmittance measurement of the CuO film was performed by a UV-Vis spectrophotometer. Band gap energy of the film was determined as 1.74 eV under indirect band gap assumption. Current-voltage (I-V) measurements of the CuO/n-Si heterojunctions were performed under illumination and in the dark to reveal the photovoltaic and electrical properties of the produced samples. From the I-V measurements, it was revealed that the CuO/n-Si heterojunctions produced by thermal evaporation exibit excellent rectifying properties in dark and photovoltaic properties under illumination. Conversion efficiencies of the CuO/n-Si solar cells are comparable to those of CuO/n-Si produced by other methods described in the literature.
Characterization of Cupric Oxide Thin Films Prepared by Nebulizer Spray Technique
(Elsevier, 2021) Ozmentes, Resit
In this study, copper oxide thin films have been prepared by nebulizer spray technique using aqueous solution of Copper(II) acetate monohydrate at 400 degrees C substrate temperature and investigated by employing XRD, SEM, UV-Vis spectroscopy techniques. XRD measurements indicated that the copper oxide thin films have been in monoclinic crystal system the cubic CuO phase structure. The SEM images showed that nanostructured particles are uniformly arranged and accumulate on the substrate to form the thin film layer. UV-Vis spectrum measurements showed that average transmission of the films was about 40% in the visible region and the optical energy gap of the films was found 1.72 eV. (c) 2021 Elsevier Ltd. Selection and peer-review under responsibility of the scientific committee of the International Congress on Semiconductor Materials and Devices, ICSMD2018.
Comparison of Electrical Properties of Cuo/N-si Contacts With Cu/N-si
(Sciendo, 2020) Ozmentes, Resit; Temirci, Cabir
In this study, CuO/n-Si/A1 heterojunction contacts were fabricated by thermal evaporation technique. Electrical characteristics of the samples were investigated with the current-voltage (I-V), capacitance-voltage/frequency (C-V/f), and conductance voltage (G/V) measurements at room temperature. Also, Cu/n-Si/Al Schottky contact was produced as a reference sample to investigate the electrical properties of the samples. The values of ideality factor (n), barrier height (Phi(b)) and series resistance (R-s) of the samples were calculated from the forward bias current-voltage (I-V) and reverse bias capacitance-voltage (C-V) characteristics. Also, for checking the consistency of the results, Cheung and Norde functions were used. The experimental result values of CuO/n-Si contact were compared with the values of the reference Cu/n-Si Schottky diode. It was observed that the values of the ideality factor and barrier height of the CuO/n-Si heterojunction were higher than those of the Cu/n-Si Schottky contact, while the series resistance was lower. Also, it has been observed that the value of capacitance decreased with increasing frequency and after a certain value of frequency it was almost constant. The ideality factor of CuO/n-Si/Al heterostructure is about 2.40 and so, it is not close to the ideal behavior.
Vacuum Ultraviolet Spectroscopic Analysis of Structural Phases in Tio2 Sol-Gel Thin Films
(Mdpi, 2025) Vasconcelos, Helena Cristina; Meirelles, Maria; Ozmentes, Resit; Korkut, Abdulkadir
This study investigates the structural and electronic transitions of sol-gel derived titanium dioxide (TiO2) thin films using vacuum ultraviolet (VUV) spectroscopy, to elucidate the impact of annealing-induced phase evolution. As the annealing temperature increased from 400 degrees C to 800 degrees C, the films transitioned from amorphous to anatase, mixed anatase-rutile, and finally rutile phases. VUV spectroscopy revealed distinct absorption features: a high-energy sigma -> pi* transition below 150 nm, associated with bonding to antibonding orbital excitations, and lower-energy absorption bands in the range 175-180 nm and near 280 nm, attributed to pi -> pi* and t2g(pi) -> t*2g(pi*) transitions, respectively. These spectral features highlight the material's intrinsic electronic states and defect-related transitions. A slight redshift of the absorption band from 176 nm to 177 nm with annealing reflects bandgap narrowing, attributed to increased rutile content, crystallite growth, and defect-induced effects. Broadening and additional absorption features around 280 nm were attributed to oxygen vacancies and reduced titanium oxidation states (Ti3+), as corroborated by X-ray photoelectron spectroscopy (XPS). XPS further confirmed the presence of Ti3+ species and oxygen vacancies, providing complementary evidence of defect-mediated transitions observed in the VUV spectra. While complementary techniques such as X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed phase transitions and the reduction of hydroxyl groups, respectively, VUV spectroscopy uniquely captured the dynamic interplay between structural defects, phase evolution, and optical properties. This study underscores the utility of VUV spectroscopy as a powerful tool for probing the electronic structure of TiO2 films, offering insights critical for tailoring their functional properties in advanced applications.