Resistive switching in FTO/CuO-Cu2O/Au memory devices

Memristors are considered to be next-generation non-volatile memory devices owing to their fast switching and low power consumption. Metal oxide memristors have been extensively investigated and reported to be promising devices, although they still suffer from poor stability and laborious fabrication process. Herein, we report a stable and power-efficient memristor with novel heterogenous electrodes structure and facile fabrication based on CuO-Cu2O complex thin films. The proposed structure of the memristor contains an active complex layer of cupric oxide (CuO) and cuprous oxide (Cu2O) sandwiched between fluorine-doped tin oxide (FTO) and gold (Au) electrodes. The fabricated memristors demonstrate bipolar resistive switching (RS) behavior with a low working voltage (~1 V), efficient power consumption, and high endurance over 100 switching cycles. We suggest the RS mechanism of the proposed device is related to the formation and rupture of conducting filaments inside the memristor. Moreover, we analyze the conduction mechanism and electron transport in the active layer of the device during the RS process. Such a facile fabricated device has a promising potential for future memristive applications

InGaAs Quantum Well Grown on High-Index Surfaces for Superluminescent Diode Applications

The morphological and optical properties of In0.2Ga0.8As/GaAs quantum wells grown on various substrates are investigated for possible application to superluminescent diodes. The In0.2Ga0.8As/GaAs quantum wells are grown by molecular beam epitaxy on GaAs (100), (210), (311), and (731) substrates. A broad photoluminescence emission peak (~950 nm) with a full width at half maximum (FWHM) of 48 nm is obtained from the sample grown on (210) substrate at room temperature, which is over four times wider than the quantum well simultaneously grown on (100) substrate. On the other hand, a very narrow photoluminescence spectrum is observed from the sample grown on (311) with FWHM = 7.8 nm. The results presented in this article demonstrate the potential of high-index GaAs substrates for superluminescent diode applications

Investigation of the Influence of the As-Grown ZnO Nanorods and Applied Potentials on an Electrochemical Sensor for In-Vitro Glucose Monitoring

The influence of the as-grown zinc oxide nanorods (ZnO NRs) on the fabricated electrochemical sensor for in vitro glucose monitoring were investigated. A direct growth of ZnO NRs was performed on the Si/SiO2/Au electrode, using hydrothermal and sol-gel techniques at low temperatures. The structure, consisting of a Si/SiO2/Au/GOx/Nafion membrane, was considered as a baseline, and it was tested under several applied potential 0.1–0.8 V. The immobilized working electrode, with GOx and a nafion membrane, was characterized amperometrically using a source meter Keithely 2410, and an electrochemical impedance Gamry potentiostat. The sensor exhibited the following: a high sensitivity of ~0.468 mA/cm2 mM, a low detection limit in the order of 166.6 µM, and a fast and sharp response time of around 2 s. The highest sensitivity and the lowest limit of detection were obtained at 0.4 volt, after the growth of ZnO NRs. The highest net sensitivity was obtained after subtracting the sensitivity of the baseline, and it was in the order of 0.315 mA/cm2·mM. The device was tested with a range of glucose concentrations from 1–10 mM, showing a linear line from 3–8 mM, and the device was saturated after exceeding high concentrations of glucose. Such devices can be used for in vitro glucose monitoring, since glucose changes can be accurately detected

An Electrochemical Glucose Sensor Based on Zinc Oxide Nanorods

A glucose electrochemical sensor based on zinc oxide (ZnO) nanorods was investigated. The hydrothermal sol–gel growth method was utilized to grow ZnO nanorods on indium tin oxide-coated glass substrates. The total active area of the working electrode was 0.3 × 0.3 cm2 where titanium metal was deposited to enhance the contact. Well aligned hexagonal structured ZnO nanorods with a diameter from 68 to 116 nm were obtained. The excitonic peak obtained from the absorbance spectroscopy was observed at ~370 nm. The dominant peak of Raman spectroscopy measurement was at 440 cm−1, matching with the lattice vibration of ZnO. The uniform distribution of the GOx and Nafion membrane that has been done using spin coating technique at 4000 rotations per minute helps in enhancing the ion exchange and increasing the sensitivity of the fabricated electrochemical sensor. The amperometric response of the fabricated electrochemical sensor was 3 s. The obtained sensitivity of the fabricated ZnO electrochemical sensor was 10.911 mA/mM·cm2 and the lower limit of detection was 0.22 µM

Effects of high‑temperature annealing on the performance of copper oxide photodetectors

Copper oxide thin films are grown using copper nanofilms oxidized at high annealing temperatures. The thin film crystallinity and surface morphology are probed using the X-ray diffractometer and scanning electron microscopy, indicating that the crystalline quality of the copper oxide thin films is improved by increasing the annealing temperature. Under ultraviolet–visible light illumination, the fabricated device with thin films annealed at 900 °C and the corresponding bandgap of 2.8 eV demonstrates the high responsivity of 15.1 A/W and maximum detectivity of 4.52 × 1012 cmHz1/2/W. The photosensitivity of thin films annealed at 900 °C is more than ten times higher than that of thin films annealed at 800 °C. The fabricated device works as a visible–ultraviolet photodetector and maintains uniform and stable performance for a tested period of eight weeks