Micro / nano- structuralized interfaces of conductive and transparent thin-film microelectrodes for biomedical application (original) (raw)
Related papers
Electrochemical and Solid State Letters, 2010
Al-doped ZnO ͑AZO͒ thin films were grown by atomic layer deposition ͑ALD͒ for use as transparent conductive oxides on high aspect ratio Si microrod arrays. The ALD-deposited AZO films showed high optical transmittance and electrical conductivity despite their polycrystalline structures and resulted in a superior conformal coating on the surface and side regions of the Si microrods. The films also exhibited an electrical performance identical to that of the AZO film on a flat Si substrate. These results revealed that ALD-deposited AZO films are promising candidates for electrodes in the next-generation optoelectronic devices based on low dimensional structures, which require conformal coating.
ZnO/Ag/ZnO multilayer films for the application of a very low resistance transparent electrode
Applied surface science, 2006
Transparent conductive ZnO/Ag/ZnO multilayer electrodes having much lower electrical resistance than the widely used transparent electrodes were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of Ag. An Ag film with different thickness was used as intermediate metallic layers. The optimum thickness of Ag thin films was determined to be 6 nm for high optical transmittance and good electrical conductivity. With about 20-25 nm thick ZnO films, the multilayer showed high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of the multilayers were changed mainly by Ag film properties. A high quality transparent electrode, having sheet resistance as low as 3 ohm/sq and high transmittance of 90% at 580 nm, was obtained and could be reproduced by controlling the preparation parameter properly. The above property is suitable as transparent electrode for dye sensitized solar cells (DSSC).
Electrodeposition of ZnO Nanorod Arrays on Transparent Conducting Substrates–a Review
Electrochimica Acta, 2014
ZnO nanorods (NRs) are promising components in a wide range of nanoscale devices for future applications in photocatalysis, solar cells, optical devices and biochemical sensing. The nanorods in the form of arrays vertically oriented to the substrate may be obtained by electrochemical deposition but morphology of the film is very sensitive to the synthesis conditions. This article provides a comprehensive review on various electrosynthesis procedures developed to obtain the nanorods of desired structure, diameter, density on the substrate. We discuss the growth mechanisms and influence of different parameters such as the type and concentration of Zn 2+ and OH − precursors, the value of applied potential or current density on the morphology of obtained ZnO films and the role of various structural modifiers on the shape of ZnO nanostructures. We present a brief analysis of the influence of electrosynthesis conditions and postannealing of the samples on optical and electrical properties of ZnO nanowires deposited on the conducting substrate. A short summary of the practical applications of ZnO nanorods is also provided.
High-Efficiency Electrodeposition of Large Scale ZnO Nanorod Arrays for Thin Transparent Electrodes
Journal of The Electrochemical Society, 2011
In the present work an effective technique to synthesize large-scale c-axis oriented ZnO nanorod (NR) arrays is presented. The manuscript reports a single-step cathodic electrodeposition, either in aqueous and organic electrolytes, to fill up ultra-thin anodic nanoporous alumina templates. Prior to growing, self-ordered hexagonal array of cylindrical nanopores have been fabricated by anodizing Al thin films previously deposited onto ITO/glass substrates. The diameter and the aspect ratio of the vertically aligned nanopores are about 60 nm and 8:1, respectively. The results of this work demonstrate that using dimethyl sulfoxide (DMSO) as an electrolyte leads to a growth more homogeneous in shape and crystallinity, and with 60% deposition efficiency-the highest by now in literature. This fact is most probably due to a better infiltration of the alumina nanopores by this electrolyte. SEM and XRD analysis were employed for the study of morphology and crystalline structure of the obtained ZnO NR. These measurements showed furthermore that ZnO nanorod arrays are uniformly embedded into the hexagonally ordered nanopores of the anodic alumina membrane. DMSO proved to be an optimal electrolyte to obtain single-crystalline ZnO NR arrays, highly transparent in visible light range (80% transmittance).
Journal of Nanomaterials, 2013
ZnO thin films were deposited on patterned gold electrodes using the sol-gel spin coating technique. Conventional photolithography process was used to obtain the variable microgaps of 30 and 43 μm in butterfly topology by using zero-gap chrome mask. The structural, morphological, and electrical properties of the deposited thin films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Keithley SourceMeter, respectively. The current-voltage (I-V) characterization was performed to investigate the effect of UV light on the fabricated devices. The ZnO fabricated sensors showed a photo to dark current (Iph/Id) ratios of 6.26 for 30 μm and 5.28 for 43 μm gap electrodes spacing, respectively. Dynamic responses of both fabricated sensors were observed till 1V with good reproducibility. At the applied voltage of 1 V, the response time was observed to be 4.817 s and 3.704 s while the recovery time was observed to be 0.3738 s and 0.2891 s for 30 and 43 μm gaps...
Characterization of ZnO Thin Film as Piezoelectric for Biosensor Applications
Proceedings of International Electronic Conference on Sensors and Applications, 2014
Biosensor is an analytical device that consists of immobilized biological sensitive materials. When these materials are in contact with certain transducers, the sensor is able to convert biological signal into an electrical signal, hence allowing for certain measurement to be conducted. These sensors have the capability to detect certain human traits such as DNA, tissues, enzyme, antibody and antigen. To increase the biosensor performance, especially the interaction between the sensor and biological elements, high uniformity and good optical transmittance sensors are strongly important. Therefore, this paper will presents early characterization of biosensors using Zinc Oxide (ZnO) piezoelectric thin film deposited as sensing layer on Silicon substrate. We investigated the thin film surface morphology and optical characterization using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and UV-Visible Spectrophotometer. We found that the surface roughness of the thin film varied from 1.1 NM to 4 NM and the grain size increased with the increase of annealing temperature, thus provide high surface uniformity that will enhance the sensitivity and specificity of the sensor.
Nanostructure of the Interfaces Between ZnO, ZnO:Ga and ZnO:Al Films and Silicon
Microscopy and Microanalysis, 2012
ZnO is a promising material for use in solar cell applications which require antireflective coatings and transparent conducting materials in front contacts. Its resistivity can be reduced by appropriate doping with different group III elements, which act as donors, without sacrificing optical transmission. Besides, it constitutes a non-toxic and cheap alternative to ITO (In2O3:SnO2), which is nowadays commonly used as transparent conducting oxide (TCO) in optoelectronic devices. Al(III) is one of the cheapest elements on nature, and has been therefore one of the first candidates to be used as a dopant. However recent studies demonstrate that for similar amounts of dopant the use of Ga largely improves both the optical and electrical properties of the films. The interface between Si (used as substrate) and the corresponding TCO is a critical part of Si-based solar cells, since the conversion efficiency may be profoundly altered by the presence of recombination centers formed at the i...
Journal of Advanced Microscopy Research, 2017
The effect of electrochemical deposition duration and the heat treatment at 450 °С within 1 hour on the microstructure of ZnO thin films, including their phase composition, lattice parameters, microstrain, grain size and surface morphology is investigated. The empirical relationships allowing to predict the molar composition and the ZnO/FTO thickness ratio depending on the specific charge passing through the substrate during the film formation process have been obtained. According to scanning electron microscopy, there is a consolidation of the film crystallites after the heat treatment leading to formation of hexagonal nanorods. An average size of the crystallites before the heat treatment is 0.727 μm, and after the heat treatment it is 0.455 μm.
Effect of Al doping on the properties of electrodeposited ZnO nanostructures
In this study, Al-doped zinc oxide (AZO) nanostructures are prepared on polycrystalline fluorine-doped tin oxide (FTO)-coated conducting glass substrates from nitrates baths by the electrodeposition process at 70 °C. The electrochemical, morphological, structural and optical properties of the AZO nanostructures were investigated in terms of different Al concentration in the starting solution. It was found from the Mott–Schottky (M-S) plot that the carrier density of AZO nanostructures varied between 3.1110 20 to 5.5610 20 cm-3 when the Al concentration was between 0 and 5 mM. Atomic force microscopie (FM) images reveal that the concentration of Al has a very significant influence on the surface morphology and roughness of AZO thin films. X-ray diffraction (XRD) patterns demonstrate preferential (002) crystallographic orientation having c-axis perpendicular to the surface of the substrate and average crystallites size of the films was about 23–36 nm. As compared to pure ZnO, Al-doped ZnO exhibited lower crystallinity and there is a shift in the (002) diffraction peak to higher angles. ZnO nanostructures were found to be highly transparent and had an average transmittance of 80 % in the visible range of the spectrum. After the incorporation of Al content into ZnO the average transmittance increased and the band-gap tuning was also achieved (from 3.22 to 3.47 eV).
ELECTRODEPOSITION AND CHARACTERIZATION OF ZnO THIN FILMS FOR SOLAR CELL
2011
In this work, we investigated the chemical composition, morphology and optical properties of zinc oxide thin films deposited from a simple aqueous zinc chloride solution. The ZnO nanorod arrays were prepared and grown on fluorine doped tin dioxide (FTO) substrate at low temperature. The nanostructure images obtained by scanning electron microscopy showed that it had the wurtzite structure or hexagonal grains with rod (needle) like shape perpendicular to the substrate surface. The Xray diffraction patterns indicated that the thin films were almost pure. The preferential orientation of ZnO growth was (002), a direction that matched calculation. These nanoscale metal oxides having ordered distributions are strong electron acceptors with high electron affinity and electron mobility which improves the electric property of photoanode and charge transport due to continuous channeling along the nanorods. In this present research, we additionally developed and optimized a method electrodepos...