Browsing by Author "Saka, Kubra"

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Comprehensive Study on Fabrication, Characterization and Performance Evaluation of Ag/TiO2 and Au/Ag Memristors
(Springer, 2025) Saka, Kubra; Gokcen, Dincer; Efkere, Halil Ibrahim; Bayram, Cem; Ozcelik, Suleyman
The structure of electrodes and active materials in memristors plays a critical role in determining their electrical behavior. This study primarily focuses on Ag/TiOx/ITO and Au/Ag/TiOx/ITO memristors incorporating titanium oxide (TiOx) thin films with varying thicknesses (25, 50, and 100 nm), deposited via RF magnetron sputtering onto ITO-coated glass substrates. Comprehensive surface characterization techniques, including scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), were employed to examine the morphological, structural, and chemical properties of the films. SEM-EDX mapping revealed thickness dependent elemental distributions. AFM analysis showed increased surface roughness (1.69 to 2.15 nm) and grain size (60 to 90 nm) with increasing film thickness. XPS measurements conducted at 8-week intervals provided insights into the oxidation behavior of Ag electrodes and their surface chemistry evolution over time. Raman analysis confirmed the presence of anatase and rutile phases in the titanium oxide thin films, as evidenced by the characteristic peaks observed at 196.83 cm-1 and 607.43 cm-1, respectively. Focused ion beam (FIB) and scanning transmission electron microscopy (STEM)-EDX were also utilized to investigate elemental boundaries between the layers. Bipolar resistive switching behavior, without the need for any electroforming process, was observed in all devices within 7 days of fabrication and remained stable throughout 1000 current-voltage (I-V) cycles. After 8 weeks of storage, further endurance tests were conducted using +/- 1.5 V SET and RESET voltages, with HRS and LRS values measured at a read voltage of 0.5 V. Notably, the highest HRS/LRS ratio of 16.07 was achieved in the Ag/TiOx/ITO memristor with a 100 nm TiOx layer. These findings underscore the critical influence of oxide thickness on resistive switching performance and endurance. Furthermore, the comparative evaluation of Ag and Au-passivated Ag electrodes highlights the significance of electrode configuration in enhancing memristor reliability and long-term operational stability.
Development of Current-Voltage Measurement System for Memristors: A Comparative Study on Ag/ZnO
(IEEE-Inst Electrical Electronics Engineers Inc, 2025) Saka, Kubra; Gokcen, Dincer; Efkere, H. Ibrahim; Ozcelik, Suleyman
This study developed a portable, wireless, and low-cost measurement system to perform current-voltage (I - V) characterization of two-terminal electronic components, particularly memristors. The proposed system was designed as an embedded hardware and software platform capable of high-precision I - V measurements. The system offers significant advantages over existing measurement setups due to its compactness with Li-ion battery power supply, Bluetooth communication capability, and the MATLAB GUI-based user interface. The performance of the system was investigated by comparing it with a widely used sourcemeter. For the testing phase of the system, the Ag/ZnO/ITO memristor structure with ZnO layer produced by sputtering method and the top electrode produced by thermal evaporation were used. The active layer of the memristor was characterized using atomic force microscopy (AFM) and Raman spectroscopy. The I - V measurements were carried out using the developed system on the Ag/ZnO/ITO memristor structure and a rectifier diode. The results demonstrated a high level of compatibility with those obtained from commercial systems. The analyses conducted for measurement precision, stability and accuracy indicate that the proposed system can be a reliable characterization tool for memristors and other two-terminal electronic components. The I - V measurement system offers an alternative solution to traditional commercial measurement devices due to the advantages of portability, low power consumption, low cost, and wireless use.
Polydimethylsiloxane-Based Capacitive Motion Sensor and Its Read-Out Circuit
(Wiley, 2021) Yildirim, Omer; Bozyel, Ibrahim; Saka, Kubra; Kayikcioglu, Temel; Gokcen, Dincer
A capacitive motion sensor that can detect human walking and motions up to a certain distance was designed using polydimethylsiloxane (PDMS) as the primary sensor material. A read-out circuit was designed to detect capacitive coupling with the sensor material caused by the motion in the surrounding. The read-out circuit consists of sensing, filtering, and amplifying stages. A high-pass filter was used to avoid DC components, and to eliminate adverse impacts of 50Hz noise in the sensing signal, a sixth-order low-pass filter consisting of active Sallen-Key and passive RC filters was utilized. The signals obtained from the complete read-out circuit revealed that the sensor system could accurately detect human movements up to 2 m away. Also, different signal patterns were obtained from the output of the sensor system for various human motions.
A Simple Yet Effective Approach for Recognition of Convex Geometric Shapes
(IEEE, 2018) Saka, Kubra; Ozturk, Mehmet
Automated shape recognition is a common problem which has been faced in computer vision applications. The feature(s) used to identify shapes is important for an accurate and fast method. Perimeter curve analysis is a widely used feature basis in this field because of its quick and easy calculation properties. This study proposes to use perimeter curve inflection points analysis to identify 2D convex geometric shapes. The proposed method is independent from translation, rotation, and scale of the geometric objects.