Papers by Keyword: Zinc Oxide (ZnO)

Abstract: In this study, ZnO nanowire field-effect transistor (FET) with an aluminium-doped ZnO (AZO) and an aluminium (Al) dual layer source and drain contact are fabricated and temperature dependent characteristics in the range of 200 – 300 K are analyzed through experimental measurements. The effect of temperature on threshold voltage, subthreshold slope, transconductance, and field effect mobility are analysed. The transfer curve exhibits a parallel shift toward a negative gate voltage direction with a negative shift of the threshold voltage, an increase in the subthreshold slope, and a field-effect mobility as the temperature rises. The electrical properties of the transistors demonstrate typical behaviour at various temperatures.

Abstract: Indium gallium zinc oxide fin-field effect transistor (IGZO FinFET) characteristics are investigated and then compared with Zinc oxide fin-field effect transistor (ZnO FinFET) and the Silicon fin-field effect transistor (Si FinFET). This was done using 3D simulation. The threshold voltage for Si, ZnO, and IGZO is 0.75 V, 0.30 V and 0.05 V respectively. The silicon device has the highest transconductance (5.0 x 10^-7 S) and performs better than the other devices because it has less fixed charge defects. IGZO has the second-best value of Gm (3.6 x 10^-7 S), ZnO has the least value of Gm (3.4 x 10^-7 S). Si device has the least drain current (I_DS) value of 2.0 x 10^-7 A, ZnO device has a better I_DS value of 6.2 x 10^-6 A while IGZO device has the best I_DS value of 1.6 x 10^-5 A. IGZO is better than Si by two (2) order magnitude. The field effect mobility is 50.0 cm²/Vs for all three devices.

Abstract: The last 19 years have seen intense research made on zinc oxide (ZnO) material mainly due to the ability of converting the natural n-type material into p-type. For a long time, the p-type state was impossible to attain and maintain. The review focuses on ways of improving the doped ZnO material which acts as a channel for nanowire field effect transistor (NWFET) and biosensor. The biosensor has specific binding which is called functionalisation achieved by attaching a variety of compounds on the designated sensing area. Reference electrodes and buffers are used as controllers. Top-down fabrication processes are preferred over bottom-up because they pave way for mass production. Different growth techniques are reviewed and discussed. Strengths and weaknesses of the FET and sensor are also reviewed.

Abstract: 3D Simulation was carried out and compared with fabricated ZnO NWFET. The device had the following electrical output characteristics: mobility value of 10.0 cm²/Vs at a drain voltage of 1.0 V, threshold voltage of 24 V, and subthreshold slope (SS) of 1500 mV/decade. The simulation showed that the device output results are influenced by two main issues: (i) contact resistance (R_con ≈ 11.3 MΩ) and (ii) interface state trapped charge number density (Q_IT = 3.79 x 10¹⁵ cm^-2). The Q_IT was derived from the Gaussian distribution that depends on two parameters added together. These parameters are: an acceptor-like exponential band tail function g_GA(E) and an acceptor-like Gaussian deep state function g_TA(E). By de-embedding the contact resistance, the simulation is able to improve the device by producing excellent field effect mobility of 126.9 cm²/Vs.

Abstract: Multi-angular branched ZnO microstructures with rods-shaped tips and nanopushpins with hexagonal cap on top have been synthesized by a simple thermal treatment process of compacted ZnS powder used as starting material and substrate. The structures have been grown at different temperatures (800, 900 and 1000 °C) for 60 min, in a constant nitrogen environment at atmospheric pressure via a catalyst-free process. XRD results of the as-grown products from ZnS powder show a significant reduction in the cubic zincblende phase to the hexagonal wurtzite phase with the increase of treatment temperature, as compared to the bulk value. Post-anneal analyses indicated that the transformation of morphologies of the as-grown structures also depends strongly on the treatment temperature. The proposed method represents an easy and economical way to grow complex structures of ZnO, with a relatively short time, furthermore, without the neediness of use an external substrate to grow. These new and interesting nanostructures have potential in applications such as optoelectronics.

Abstract: ZnO Nano and microstructures were obtained by thermal oxidation using Zn powders as source. To achieve those structures, the Zn powders were annealed at 650°C and 750°C under oxygen environment and atmospheric pressure. SEM results show that these experimental conditions promote the formation of hollow spherical microstructures with nanowires and nano-swords in each sphere. As was observed, the nanostructures start growing from the bottom surface of the spheres unlike those that were reported recently. The EDS results clearly show that those hollow spheres in the deep part make a compound with Zn and the top surface is mainly composed of ZnO. CL emission spectra show a main green emission that belongs to the sphere’s bottom surface; this emission is correlated to the existing defects that are presented. These results could allow the prediction of a possible growth mechanism under specific conditions.

Abstract: Titanium dioxide is prepared by sol gel method from titanium tetraisopropoxide (TTIP) as precursor and likewise zinc oxide is prepared by sol gel method from zinc acetate dehydrate (ZAD) as precursor. The composite sols are prepared in three different molar ratios 90TiO2:10ZnO, 70TiO2:30ZnO and 50TiO2:50ZnO. Thin film deposition is carried out by dip coating technique. Crystal structure, surface morphology and photocatalytic activity of the prepared nanocomposite thin films are investigated. The antibacterial activity of the prepared nanocomposite thin film against E-coli ATCC 25922 bacteria is examined by placing the thin film in standard aqueous E-coli medium under UV light for 1, 2, 3 and 4 hours and then counting the bacteria with Standard Plate Count Agar (SPC) technique. The prepared thin films have shown strong antibacterial activity in the presence of UV light and by increasing the ZnO molar ratio from 10 to 50, antibacterial activity of the thin films decreases because of decreases in the anatase phase of the TiO2. In the dark conditions by increasing the molar ratio of ZnO, the antibacterial activity of the thin films increases and this phenomenon is related to increasing the zinc ions in the thin films.

Abstract: A facile method has been developed to fabricate ZnO microstructures by a solution route at an 80°C. The microstructures with various morphologies were fabricated in water or anhydrous ethanol by using polyvinylpyrrolidone and cetyltrimethylammonium bromide as surfactants. ZnO rods with aspect ratios up to 30 have been created successfully in water through a hydrothermal process, while novel shuttle-like ZnO microstructures were fabricated in anhydrous ethanol using a similar procedure. ZnO rods revealed wurtzite-type crystal structure according to their X-ray diffraction (XRD) patterns. The morphologies of ZnO microstructures were adjusted conveniently by changing solvents and surfactants. In addition, the sizes of ZnO microstructures decreased under a long reaction time. This morphological evolution of ZnO microstructures indicated that the growth of ZnO is susceptive to reaction time due to the reaction between ZnO and aqueous ammonia. The facile strategy described here would be utilizable for the preparation of various metal oxide microstructures.

Abstract: A study on the synthesis of multiwalled carbon nanotubes (MWCNT) and zinc oxide (ZnO) hybrid materials using the mecahnochemical technique has been conducted. MWCNT was dispersed in sodium dodecyl sulfate (SDS) solution. ZnO was formed at milling time between 2 and 5 hours, where at 10 hours the XRD results showed only small peaks of ZnO. This suggests that at longer milling time, the ZnO crystals were either become amorphous or have reduced in sized so as not to be detected using XRD. ZnO has also been doped with Manganese (Mn) which have affected the crystal structure and surface morphology of the sample.Keywords:Doping, Manganese nitrate, Mechanochemical technique, Multiwalled carbon nanotubes (MWCNT), Surfactant method , Zinc Oxide (ZnO)

Abstract: This study highlights the structural, morphological, photovoltaic and electron transport properties of zinc oxide-multi-walled carbon nanotubes (ZnO-MWCNTs) based dye-sensitized solar cell (DSSC) prepared at different concentrations of 0.0, 0.1, 0.3 and 0.5 wt.%. The ZnO-MWCNTs thin films were prepared by a chemical bath deposition method. X-ray diffraction (XRD) analysis proved the formation of hexagonal wurtzite of the samples. The crystallite sizes, D of ZnO-MWCNTs was measured varies from 21 nm to 11 nm. The oat-like ZnO nanoflakes structure and the presence of MWCNTs were captured by field-emission scanning electron microscopy (FESEM) analysis. Transmission electron microscopy (TEM) analysis measured the inner (~6.81 nm) and outer (~28.31 nm) diameter of MWCNTs. The optimum concentration of 0.1 wt.% MWCNTs produced the highest photocurrent density, J_sc of 13.5 mA/cm², open-circuit voltage, V_oc of 0.149 V, fill factor, FF of 0.406 and power conversion efficiency, PCE of 0.817 %. Optimum doping of 0.1 wt.% MWCNTs generated short electron lifetime, τ_eff of 0.67 ms, low effective electron chemical diffusion coefficient, D_eff of 9.5 x 10^-8 cm² s^-1 and higher electron recombination rate, k_eff of 1497.48 s^-1. The addition of MWCNTs has influenced the structural, morphological, photovoltaic and electron transport properties of ZnO-MWCNTs based DSSC.