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- MakaleYalnız künye2019Scopus SJRQ1Circuit implementation of nano-scale TiO2 memristor using only metal-oxide-semiconductor transistors
Gul, Fatih
A metal-oxide-semiconductor (MOS)-based circuit model that emulates a TiO2 memristor is proposed in this study. First, a TiO2 (10-nm active layer thickness)-based memristor device was fabricated. The structural properties of the device were confirmed via energy dispersive X-ray spectroscopy. The memristive characteristics of the device were resolved by applying a time-dependent voltage. The typical pinched hysteresis memristive loops of the current-voltage curves were obtained. After physical implementation and characterization of the device, a circuit model was implemented using only four MOS transistors to emulate the fabricated TiO2 memristor. In addition to emulating the fabricated memristor, the proposed circuit model is suitable for use in general memristor-based applications. No active element or circuit blocks were used in the circuit to achieve memristive characteristics. The simulation and experimental results are in good agreement; moreover, the circuit is very simple compared to those presented in previous studies in the literature and it was able to emulate the fabricated memristor. All simulations were completed using 180 nm TSMC CMOS process parameters.
AtıfScopus38WoS35OpenAlex40
İncele - MakaleAçık Erişim2019Scopus SJRQ2Addressing the sneak-path problem in crossbar RRAM devices using memristor-based one Schottky diode-one resistor array
Gül, Fatih
Resistive random access memories (RRAMs) are favorable contenders in the race towards future technologies. Moreover, the desirable properties of memristor-based RRAM devices make them very good competitors in this field. The sneak paths problem poses one of the main difficulties in the construction of crossbar memory devices. This problem can be effectively suppressed by applying the 1diode-1resistor (1D1R) design structure. The Schottky diode has many advantages compared to the PN junction diode. The low-power (∼1 µW) ZnO active-layered thin-film (60 nm thick) one Schottky diode-one memristor device fabricated in this study included a top Ag electrode and a bottom Al electrode. The material makeup of the device was confirmed via energy dispersive X-ray spectroscopy (EDAX). The memristive and Schottky diode characteristics of the Ag/ZnO/Al device were resolved by measuring the time-dependent voltage/current. The characteristic pinched hysteresis memristive loops were observed at the first quadrant of the current-voltage plane, whereas the diode curves were seen at the third quadrant. Using the current-voltage curves, the height of the Schottky barrier, ideality factor and threshold voltage of the Schottky diode were found to be 0.68 eV, 3.75 and 0.49 V, respectively. After physical implementation and characterization of the one diode-one memristor device, its anti-crosstalk characteristics were investigated. Taking into account the 10% read margin, the maximum crossbar size was found to be 87.
AtıfScopus121WoS115OpenAlex127İncele - MakaleYalnız künye2018Scopus SJRQ1The Fabrication and MOSFET-Only Circuit Implementation of Semiconductor Memristor
Babacan, Yunus; Yesil, Abdullah; Gul, Fatih
In this paper, a ZnO-based semiconductor thin film memristor (300 nm in thickness) device is fabricated using metallic top and bottom electrodes by direct-current reactive magnetron sputter. The memristive characteristics of the device were completed by time-dependent current-voltage (I-V-t) measurements, and the typical pinched hysteresis I-V loops of the memristor were observed. This paper is continued with the designing memristor emulator circuit, which has only four MOS transistors. The proposed circuit is suitable both for emulating the fabricated memristor and for using general memristor-based applications. Any circuit blocks such as a multiplier or active element are not used in the circuit to obtain memristive characteristics. All results of the proposed memristor emulator circuit are compatible with general characteristics of the fabricated semiconductor device. The MOSFET-based proposed memristor emulator circuit is laid out in the Analog Design Environment of Cadence Software using 180-nm TSMC CMOS process parameters and its layout area is 366 μm2. So as to show its performance, the dependences of the operating frequency and process corner as well as effects of radical temperature changes have been investigated in the simulation results section.
AtıfScopus94WoS77OpenAlex98İncele - MakaleYalnız künye2018Scopus SJRQ2A novel OTA-based circuit model corroborated by an experimental semiconductor memristor
Gul, Fatih; Babacan, Yunus
A semiconductor memristor device based on a 300-nm ZnO thin film was fabricated by direct-current reactive sputter. The memristive behavior of this device was confirmed by time dependent current–voltage (I-V-t) measurements, and the distinctive pinched hysteresis I-V loops of the memristor were observed. Structural analysis of the ZnO memristor was carried out using both X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). After physical implementation of the memristor, an operational transconductance amplifier (OTA) based memristor circuit was designed to emulate the ZnO-based semiconductor memristor for use in memristor-based circuit applications. All simulations were in good agreement with experimental results. In addition, a comparison of the proposed circuit with other memristor emulators was presented.
AtıfScopus29WoS27OpenAlex29İncele - MakaleYalnız künye2018Scopus SJRQ1Carrier transport mechanism and bipolar resistive switching behavior of a nano-scale thin film TiO2 memristor
Gul, Fatih
A titanium dioxide (TiO2) based memristor device having an active layer thickness of 10 nm was fabricated using radio frequency (RF) reactive sputtering and its resistive switching characteristics and carrier transport mechanisms were investigated. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to confirm the structural properties of the device. Measurement of the time-dependent current-voltage (I-V-t) was used to characterize resistive switching and memristive behavior. The characteristic pinched hysteresis I-V loops of the memristor were apparent. Bipolar and homogeneous resistive switching characteristics and a forming voltage of 2 V were detected in the device. The retention time exceeded 103 s and the endurance test was reasonably acceptable. In addition, the carrier transport mechanism of the device was revealed. The linear region of the low electric field demonstrated ohmic behavior, whereas the non-linear high electric field region was dominated by a Schottky emission carrier transport mechanism. A Poole-Frenkel emission mechanism acted as a secondary conduction mechanism. It was proposed that the Poole-Frenkel and Schottky emission mechanisms were associated with oxygen vacancies in the TiO2.
AtıfScopus69WoS69OpenAlex77İncele - MakaleYalnız künye2017Scopus SJRQ2Bipolar resistive switching and conduction mechanism of an Al/ZnO/Al-based memristor
Gul, Fatih; Efeoglu, Hasan
In this study, a direct-current reactive sputtered AliZnO/Al-based memristor device was fabricated and its resistive switching (RS) characteristics investigated. The optical and structural properties were confirmed by using UV vis spectrophotometry and x-ray diffraction, respectively. The memristive and resistive switching characteristics were determined using time dependent current voltage (I-V-t) measurements. The typical pinched hysteresis I-V loops of a memristor were observed. In addition, the device showed forming-free, uniform and bipolar RS behavior. The low electric field region exhibited ohmic conduction, while the Schottky emission (SE) was found to be the dominant conduction mechanism in the high electric field region. A weak Poole-Frenkel (PF) emission also appeared. In conclusion, it was suggested that the SE and PF mechanisms were related to the oxygen vacancies in the ZnO. (C) 2016 Elsevier Ltd. All rights reserved.
AtıfWoS62OpenAlex76İncele - MakaleAçık Erişim2017Scopus SJRQ1ZnO and ZnO1−x based thin film memristors: The effects of oxygen deficiency and thickness in resistive switching behavior
Gul, Fatih; Efeoglu, Hasan
In this study, direct-current reactive sputtered ZnO and ZnO1−x based thin film (30 nm and 300 nm in thickness) memristor devices were produced and the effects of oxygen vacancies and thickness on the memristive characteristics were investigated. The oxygen deficiency of the ZnO1−x structure was confirmed by SIMS analyses. The memristive characteristics of both the ZnO and ZnO1−x devices were determined by time dependent current–voltage (I-V-t) measurements. The distinctive pinched hysteresis I-V loops of memristors were observed in all the fabricated devices. The typical homogeneous interface and filamentary types of memristive behaviors were compared. In addition, conduction mechanisms, on/off ratios and the compliance current were analyzed. The 30 nm ZnO based devices with native oxygen vacancies showed the best on/off ratio. All of the devices exhibited dominant Schottky emissions and weaker Poole-Frenkel conduction mechanisms. Results suggested that the oxygen deficiency was responsible for the Schottky emission mechanism. Moreover, the compliance currents of the devices were related to the decreasing power consumption as the oxygen vacancies increased.
AtıfScopus68WoS63OpenAlex71İncele