Microwave oven fabricated hybrid memristor devices for non-volatile memory storage

© 2014 IOP Publishing Ltd. Novel hybrid non-volatile memories made using an ultra-fast microwave heating method are reported for the first time. The devices, consisting of aligned ZnO nanorods embedded in poly (methyl methacrylate), require no forming step and exhibit reliable and reproducible bipolar resistive switching at low voltages and with low power usage. We attribute these properties to a combination of the high aspect ratio of the nanorods and the polymeric hybrid structure of the device. The extremely easy, fast and low-cost solution based method of fabrication makes possible the simple and quick production of cheap memory cells

Method to reduce the formation of crystallites in ZnO nanorod thin-films grown via ultra-fast microwave heating

© 2018 This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices

Ovarian Transcriptomic Analyses in the Urban Human Health Pest, the Western Black Widow Spider

Due to their abundance and ability to invade diverse environments, many arthropods have become pests of economic and health concern, especially in urban areas. Transcriptomic analyses of arthropod ovaries have provided insight into life history variation and fecundity, yet there are few studies in spiders despite their diversity within arthropods. Here, we generated a de novo ovarian transcriptome from 10 individuals of the western black widow spider (Latrodectus hesperus), a human health pest of high abundance in urban areas, to conduct comparative ovarian transcriptomic analyses. Biological processes enriched for metabolism—specifically purine, and thiamine metabolic pathways linked to oocyte development—were significantly abundant in L. hesperus. Functional and pathway annotations revealed overlap among diverse arachnid ovarian transcriptomes for highly-conserved genes and those linked to fecundity, such as oocyte maturation in vitellogenin and vitelline membrane outer layer proteins, hormones, and hormone receptors required for ovary development, and regulation of fertility-related genes. Comparative studies across arachnids are greatly needed to understand the evolutionary similarities of the spider ovary, and here, the identification of ovarian proteins in L. hesperus provides potential for understanding how increased fecundity is linked to the success of this urban pest

Percolation threshold enables optical resistive‐memory switching and light‐tuneable synaptic learning in segregated nanocomposites

An optical memristor where the electrical resistance memory depends on the history of both the current flowing through the device and the irradiance of incident light onto it is demonstrated. It is based on a nanocomposite consisting of functionalized gold nanoparticles in an optically active azobenzene polymer matrix. The composite has an extremely low percolation threshold of 0.04% by volume for conductivity because of the aggregation of the conducting nanoparticles into filamentary nanochannels. Optical irradiation results in photomechanical switching through expansion of the thin film from above to below the percolation threshold, giving a large LOW/HIGH resistance ratio of 103. The device acts as an artificial synapse, the conductivity or plasticity of which can be independently modulated, either electrically or optically, to enable tunable and reconfigurable synaptic circuits for brain‐inspired artificial intelligent or visual memory arrays. The lifetime of the resistive‐memory states is also optically controllable, which enables spatial modulation of long‐ and short‐term memory

Solution-processable, niobium-doped titanium oxide nanorods for application in low-voltage, large-area electronic devices

We report for the first time the one-step synthesis of solution-processable, highly crystalline, niobiumdoped titanium dioxide (Nb-TiO2) nanorods in the anatase phase by the hydrolytic condensation of Ti(OiPr)4 and niobium(V) ethoxide using oleic acid as a structure-directing and stabilising agent. These novel surface-stabilised nanorods can be easily dispersed in common solvents at relatively high concentration (B10%) and deposited as uniform, thin and transparent films on planar substrates for the fabrication of electronic devices. The small size of the nanoparticles synthesized represents an important advance in achieving high-k dielectric thin films smooth enough to be suitable for OFET applications and the plastic electronics filed in general. Preliminary investigations show that the dielectric constant, k, of niobium-doped (7.1 wt%) titanium dioxide (Nb-TiO2) nanorods at frequencies in the region of 100 kHz–1 MHz, are more a third greater (k 4 8) than that (k = 6) determined for the corresponding undoped titanium dioxide (TiO2) nanorods. The current–voltage (J–V) behaviour of these devices reveal that niobium-doping improves, by reducing, the leakage current of these devices, thereby preventing hard dielectric breakdown of devices incorporating these new nanorods

Persistent near-infrared photoconductivity of ZnO nanoparticles based on plasmonic hot charge carriers

We report on the coupling of ZnO nanoparticles with plasmonic gold nanoislands in a solution processed photodetector, which results in a clear enhancement in the optical absorption and the electrical responsivity of ZnO nanoparticles to cover the visible and the near-IR (NIR) spectral range, well beyond its intrinsic optical absorption. This enhancement, which arises from the coupling between ZnO nanoparticles and the plasmonically mediated hot electron generation in the Au plasmonic nanoislands, results in a significant plasmonically driven photoresponse in the NIR of 2.5×10-5 A/W. The recorded photocurrent exhibits a persistent behaviour, which is attributed to surface defect states in the ZnO nanoparticles. This study provides a route to solution processed, low-cost device fabrication schemes with important implications on low processing temperature optoelectronics technology to enhance the performance of photovoltaic devices over a wide solar spectrum. Additionally, this unusual behaviour paves the way towards harnessing plasmonic resonances to probe and examine the surface defects of metal oxide semiconductors

Sonographic Assessment of Uterine Biometry for the Diagnosis of Diffuse Adenomyosis in a Tertiary Outpatient Clinic

Background: to compare several uterine biometric parameters at transvaginal ultrasound (TVUS) between adenomyosis and non-adenomyosis uteri and evaluate their role for the diagnosis of diffuse adenomyosis. Methods: prospective observational study conducted between the 1 February 2022 and the 30 April 2022. In this case, 56 patients with TVUS diagnosis of adenomyosis were included. A 1:1 ratio age and parity-matched group of non-adenomyosis patients was selected. We compared sonographic uterine biometric parameters (longitudinal (LD), anteroposterior (APD) and transverse (TD) diameters, volume, simple and complex diameter ratios) and investigated their diagnostic performance. Results: all sonographic parameters were significantly different between the study groups, except for TD/(LD+APD). Optimal cut-off values of APD and LD/APD showed the best sensitivity and specificity. APD diameter equal or superior to 39.5 mm (95% CI, 36.2–42.8) had sensitivity of 0.70 (95% CI, 0.57–0.80), specificity of 0.71 (95% CI, 0.59–0.82) and accuracy of 0.75 (95% CI, 0.66–0.84). LD/APD equal or inferior to 2.05 (95% CI, 1.96–2.13) showed sensitivity and specificity of 0.70 (95% CI, 0.57–0.80) each and accuracy of 0.72 (95% CI, 0.62–0.81). Conclusions: several biometric uterine parameters at TVUS in fertile-aged women were statistically different between adenomyosis and non-adenomyosis uteri, though their optimal cut-off values showed low accuracy in diagnosing adenomyosis

Solution-processable, niobium-doped titanium oxide nanorods for application in low-voltage, large-area electronic devices

We report for the first time the one-step synthesis of solution-processable, highly crystalline, niobium-doped titanium dioxide (Nb-TiO2) nanorods in the anatase phase by the hydrolytic condensation of Ti(OiPr)4 and niobium(V) ethoxide using oleic acid as a structure-directing and stabilising agent. These novel surface-stabilised nanorods can be easily dispersed in common solvents at relatively high concentration (∼10%) and deposited as uniform, thin and transparent films on planar substrates for the fabrication of electronic devices. The small size of the nanoparticles synthesized represents an important advance in achieving high-k dielectric thin films smooth enough to be suitable for OFET applications and the plastic electronics filed in general. Preliminary investigations show that the dielectric constant, k, of niobium-doped (7.1 wt%) titanium dioxide (Nb-TiO2) nanorods at frequencies in the region of 100 kHz–1 MHz, are more a third greater (k > 8) than that (k = 6) determined for the corresponding undoped titanium dioxide (TiO2) nanorods. The current–voltage (J–V) behaviour of these devices reveal that niobium-doping improves, by reducing, the leakage current of these devices, thereby preventing hard dielectric breakdown of devices incorporating these new nanorods