ZnO-Cu2O core-shell nanowires as stable and fast response photodetectors (original) (raw)
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ZnO Branched Nanowires and the p-CuO/n-ZnO Heterojunction Nanostructured Photodetector
IEEE Transactions on Nanotechnology, 2000
The authors report the growth of ZnO branched nanowires on the CuO nanowires and the fabrication of p-CuO/ n-ZnO heterojunction nanostructured photodetector (PD). It was found that the hydrothermally grown ZnO branched nanowires were reasonably uniform with an average length of 200 nm and an average diameter of 50 nm. Under forward bias, it was found that turn on voltage of the fabricated PD reduced from ∼0.7 to ∼0.2 V under ultraviolet (UV) illumination. It was also found that UV-to-visible rejection ratio of the fabricated device was larger than 100.
Radial heterojunction based on single ZnO-CuxO core-shell nanowire for photodetector applications
Scientific Reports
Zno-Cu x o core-shell radial heterojunction nanowire arrays were fabricated by a straightforward approach which combine two simple, cost effective and large-scale preparation methods: (i) thermal oxidation in air of a zinc foil for obtaining ZnO nanowire arrays and (ii) radio frequency magnetron sputtering for covering the surface of the ZnO nanowires with a Cu x O thin film. The structural, compositional, morphological and optical properties of the high aspect ratio Zno-Cu x o core-shell nanowire arrays were investigated. Individual ZnO-Cu x o core-shell nanowires were contacted with pt electrodes by means of electron beam lithography technique, diode behaviour being demonstrated. Further it was found that these n-p radial heterojunction diodes based on single Zno-Cu x o nanowires exhibit a change in the current under UV light illumination and therefore behaving as photodetectors. The design and fabrication of nanostructures with complex architectures can fuel the new trends in modern technologies by enabling the development of low dimensional devices with improved performances and additional functionalities. In this context, the fabrication of one-dimensional or quasi one-dimensional nanostructures such us semiconductor heterojunctions or metal/semiconductor junctions is an attractive focus point for researchers 1-3. Such one-dimensional heterojunctions can be built in different geometries: axial, radial or hierarchical/ branched 1,2. Nanowires represent an important class of nanostructures 4,5 due to their one-dimension induced properties (high surface to volume ratio, quantum confinement, etc.), in some cases, quite different from the characteristics of the same material in the bulk form 6. Semiconductor nanowires 7 are intensively studied because of some specific features that can be easily tuned during the preparation stage 8. Such nanostructures can find applications in optoelectronic and electronic devices like nanowire lasers 9 , field effect transistors 10-13 , solar cells 14 , photodetectors 15 , photocatalysts 16 , bio-sensors 17 , etc. Furthermore, core-shell semiconductor heterojunctions lead to enhanced functionalities for a wide range of applications such as energy storage, solar cells, photocatalysis, photodetectors 18-25. Also, various UV, visible and infrared radiation photodetectors based on core-shell nanowire arrays containing CdS-ZnO 26 , CuO-Si 27 , ZnO-NiO 28 , ZnO-Cu 2 O 29 , ZnO-TiO 2 30 or CuO-ZnO 31 have been reported. Zinc oxide is a wide band gap n-type semiconductor (3.37 eV) with a high exciton binding energy (60 meV) 32. Cuprous oxide (Cu 2 O) and cupric oxide (CuO) are both naturally p-type semiconductors with direct narrow band gaps of 2.0 eV and 1.2 eV, respectively 33 , usually the mixture between these two copper oxides being labelled as Cu x O 33. A staggered gap (type II) band alignment can be obtained by combining ZnO and Cu x O in n-p core-shell heterojunction structures 34. This type II band alignment favors the spatial charge separation of electrons and holes at the interface that suppresses the recombination of photogenerated carriers 34-36. Moreover, the advantage of such core-shell heterostuctures is related to an enhancement of the charge collection efficiency at the electrodes due to the internal field which appears at the interface between the p-n semiconductors (along the length of the nanowire ~µm range) and the separation of photogenerated charges which takes place along the radius of the nanowire (~nm range) 1,36. Therefore, such ZnO-CuO core-shell radial heterojunction nanowires are
Scientific Reports
An original photodetector system based on self-connected CuO–ZnO radial core–shell heterojunction nanowire arrays grown on metallic interdigitated electrodes, operating as visible-light photodetector was developed by combining simple preparation approaches. Metallic interdigitated electrodes were fabricated on Si/SiO2 substrates using a conventional photolithography process. Subsequently, a Cu layer was electrodeposited on top of the metallic interdigitated electrodes. The CuO nanowire arrays (core) were obtained by thermal oxidation in air of the Cu layer. Afterwards, a ZnO thin film (shell) was deposited by RF magnetron sputtering covering the surface of the CuO nanowires. The morphological, structural, compositional, optical, electrical and photoelectrical properties of the CuO nanowire arrays and CuO–ZnO core–shell nanowire arrays grown on metallic interdigitated electrodes were investigated. The performances of the devices were evaluated by assessing the figures of merit of the...
ACS Applied Nano Materials, 2019
Transparent nanoscale-film heterojunctions based on Cu2O and ZnO were fabricated by atomic layer deposition and reactive magnetron sputtering. The constitutive layers exhibit high crystalline quality and a local epitaxial relation between Cu2O and ZnO was achieved with [110] Cu2O || [001] ZnO and [001] Cu2O || [010] ZnO as evidenced by high resolution transmission electron microscopy and. Cu2O films show very low resistivity and high mobility values of 9-150 Ω cm and 19 cm 2 / V s, respectively. The Cu2O/ZnO heterojunctions exhibit a non-linear rectifying behavior characteristic of a p-n junction, self-powered photo-response under 1-Sun illumination and an average transmittance of 73% in the visible region of the electromagnetic spectrum. These results are promising for all-oxide transparent electronics, photodetection and photovoltaic applications.
Photodetecting properties of single CuO–ZnO core–shell nanowires with p–n radial heterojunction
Scientific Reports
CuO–ZnO core–shell radial heterojunction nanowire arrays were obtained by a simple route which implies two cost-effective methods: thermal oxidation in air for preparing CuO nanowire arrays, acting as a p-type core and RF magnetron sputtering for coating the surface of the CuO nanowires with a ZnO thin film, acting as a n-type shell. The morphological, structural, optical and compositional properties of the CuO–ZnO core–shell nanowire arrays were investigated. In order to analyse the electrical and photoelectrical properties of the metal oxide nanowires, single CuO and CuO–ZnO core–shell nanowires were contacted by employing electron beam lithography (EBL) and focused ion beam induced deposition (FIBID). The photoelectrical properties emphasize that the p–n radial heterojunction diodes based on single CuO–ZnO core–shell nanowires behave as photodetectors, evidencing a time-depending photoresponse under illumination at 520 nm and 405 nm wavelengths. The performance of the photodetect...
Journal of Alloys and Compounds, 2017
A photoelectrochemical cell can be used as a self-powered photodetector based on the photovoltaic effect. Here, we report an effective way to enhance the self-powered photoresponse performance of the ZnO nanowire arrays (NAs)/Cu 2 O photoanodes by introducing graphene interlayers. The self-powered photodetectors based on ZnO NAs/graphene (G)/Cu 2 O have large responsivities of 21.2 mA/W and 17.1 mA/W for ultraviolet (UV) and visible light, respectively, and fast rise and decay times (0.6 ms). Introduction of the Cu 2 O film improves the visible light-harvesting ability, and the step-like band alignment between ZnO and Cu 2 O benefits the separation of photoexcited carriers. Furthermore, the graphene interlayers also contribute to the carrier separation and transfer process because of their excellent charge collection capacity. The results demonstrate the ZnO/G/Cu 2 O heterojunction can be a promising configuration for self-powered UV-visible photodetecting.
Oxide p-n Heterojunction of Cu2O/ZnO Nanowires and Their Photovoltaic Performance
Journal of Nanomaterials, 2013
Oxide p-n heterojunction devices consisting of p-Cu2O/n-ZnO nanowires were fabricated on ITO/glass substrates and their photovoltaic performances were investigated. The vertically arrayed ZnO nanowires were grown by metal organic chemical vapor deposition, which was followed by the electrodeposition of the p-type Cu2O layer. Prior to the fabrication of solar cells, the effect of bath pH on properties of the absorber layers was studied to determine the optimal condition of the Cu2O electrodeposition process. With the constant pH 11 solution, the Cu2O layer preferred the (111) orientation, which gave low electrical resistivity and high optical absorption. The Cu2O (pH 11)/ZnO nanowire-based solar cell exhibited a higher conversion efficiency of 0.27% than the planar structure solar cell (0.13%), because of the effective charge collection in the long wavelength region and because of the enhanced junction area.
Scientific reports, 2015
We have engineered the electronic structure at the interface between Cu2O and ZnO nanorods (NRs) array, through adjusting the carrier concentration of Cu2O. The electrodeposition of Cu2O at pH 11 acquired the highest carrier concentration, resulting in the largest interfacial electric field between Cu2O and ZnO, which finally led to the highest separation efficiency of photogenerated charge carriers. The optimized Cu2O/ZnO NRs array p-n heterostructures exhibited enhanced PEC performance, such as elevated photocurrent and photoconversion efficiency, as well as excellent sensing performance for the sensitive detection of glutathione (GSH) in PBS buffer even at applied bias of 0 V which made the device self-powered. Besides, the favorable selectivity, high reproducibility and extremely wide detection range, make such heterostructure a promising candidate for PEC biosensing applications, probably for the extended field of PEC water splitting or other solar photovoltaic beacons.
UV-Photodetectors based on CuO/ZnO nanocomposites
Materials Letters, 2018
CuO/ZnO nanocomposites were prepared by a simple, low temperature hydrothermal method and followed by anodization technique on Indium-doped tin oxide (ITO) coated on the glass substrate. The prepared sample was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis. All results confirmed the deposition of CuO on the surface of ZnO nanorod arrays. Further, CuO/ZnO nanocomposite-based UV photodetectors were characterized by standard I-V curves. As a result, CuO/ZnO nanocomposite devices exhibited high responsivity, photocurrent gain, and good reliability as compared to pure ZnO nanorod devices. Therefore, the nanocomposites of CuO/ZnO devices show good promise for UV photodetectors with possibility to fine-tune properties, and it is worthy of further investigation.