ABSTRACT
In the present investigation, we have fabricated copper oxide (CuO) thin film memristor by employing a hydrothermal method for neuromorphic application. The X-ray diffraction pattern confirms the films are polycrystalline in nature with the monoclinic crystal structure. The developed devices show analog memory and synaptic property similar to biological neuron. The size dependent synaptic behavior is investigated for as-prepared and annealed CuO memristor. The results suggested that the magnitude of synaptic weights and resistive switching voltages are dependent on the thickness of the active layer. Synaptic weights are improved in the case of the as-prepared device whereas they are inferior for annealed CuO memristor. The rectifying property similar to a biological neuron is observed only for the as-prepared device, which suggested that as-prepared devices have better computational and learning capabilities than annealed CuO memristor. Moreover, the retention loss of the CuO memristor is in good agreement with the forgetting curve of human memory. The results suggested that hydrothermally grown CuO thin film memristor is a potential candidate for the neuromorphic device development.
ABSTRACT
Polycrystalline CoFe2O4 thin films are deposited onto the quartz substrates by spray pyrolysis technique. Rietveld refinement analysis confirmed the films are polycrystalline in nature with spinel cubic crystal structure. Rietveld refinement analysis was employed to estimate the cation distribution in spinel lattice sites. Surface micrographs shows the granular morphology with average grain size decreases with increase in solution concentration. The presence of two characteristic absorption bands around 579 and 391cm-1 in the FTIR study confirms the formation of single phase CoFe2O4. Vibrating sample magnetometer measurement confirmed the predominant ferrimagnetic nature of thin films which confirms the maximum saturation magnetization with moderate coercivity was useful for making effective gas sensor. The gas response towards different operating temperatures, gas concentrations and solution concentrations was systematically studied. The films show the maximum gas response 70% at 0.1M solution concentration at 150°C operating temperature. The films are well selective towards NO2 as compared with other test gases with good reproducibility.
ABSTRACT
We report a study on effect of film thickness on NO2 sensing properties of sprayed WO3 thin films. WO3 thin films varying in thicknesses are deposited onto the glass substrates by simple spray pyrolysis technique by varying the volume of spray solution.Thin film gas sensors are characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL) techniques to study their physical properties. Film having thickness 745nm has shown highest gas response of 97% with 12 and 412s response and recovery times, respectively towards 100ppm NO2 concentration. Gas response of 20% is observed towards 10ppm NO2 at 200°C operating temperature. Sensitivity of the optimal sensor is 0.83%/ppm when operating at 200°C with 10ppm lower detection limit. The response of the sensor is reproducible and WO3 films are highly selective towards NO2 in presence of mist of various interfering gases viz. H2S, NH3, LPG, CO and SO2.
