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.

High aspect ratio CuO nanowires are synthesized by a simple and scalable method, thermal oxidation in air. The structural, morphological, optical, and electrical properties of the semiconducting nanowires were studied. Au-Ti/CuO nanowire and Pt/CuO nanowire electrical contacts were investigated. A dominant Schottky mechanism was evidenced in the Au-Ti/CuO nanowire junction and an ohmic behavior was observed for the Pt/CuO nanowire junction. The Pt/CuO nanowire/Pt structure allows the measurements of the intrinsic transport properties of the single CuO nanowires. It was found that an activation mechanism describes the behavior at higher temperatures, while a nearest neighbor hopping transport mechanism is characteristic at low temperatures. This was also confirmed by four-probe resistivity measurements on the single CuO nanowires. By changing the metal/semiconductor interface, devices such as Schottky diodes and field effect transistors based on single CuO p-type nanowire semiconductor channel are obtained. These devices are suitable for being used in various electronic circuits where their size related properties can be exploited. V C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4921914]In the last years, among the studies on the transition metal oxides nanostructures, 1-4 copper oxide (CuO), a p-type semiconductor with a narrow band gap (1.2 eV in bulk), attracted interest because of its properties. 2 CuO started to be regarded as a promising semiconductor due to its low cost and abundance, its environmentally friendly nature and its easy preparation in various nanostructure morphologies: wires, 5,6 rods, 7 tubes, 8 spheres, 9 flowers, 10 ribbons, 11 rings, 12 dendrites, 13 and fibers. 14,15 These CuO nanostructures have numerous applications, including gas-sensors, 9,16-18 bio-sensors, 19-21 rechargeable ions batteries, 7,22-24 supercapacitors, 10 solar cells, 25,26 memristors, 27 field emitters, 28-30 or field effect transistors. 18,31 Particularly, one dimensional semiconducting nanostructures, such as nanowires or nanotubes, defined by high aspect and large surface to bulk ratios, gained considerable attention due to the potential use in electronic devices. 5,[16][17][18][19][27][28][29][30][31][32][33][34] Up to now, different approaches were used for growing CuO nanowires including wet-chemical methods, electrochemical and hydrothermal routes, as well as thermal and plasma oxidation techniques. 35 In this work, we report on the electrical properties of CuO nanowires, obtained by thermal oxidation in air of copper substrates, 6 these one-dimensional nanostructures being suitable for fabricating devices such as diodes and field effect transistors. In order to contact single CuO nanowires, electron beam lithography (EBL) and focused ion beam induced deposition (FIBID) were employed. Using different metals as electrodes, we modified the metal/semiconductor interface, and therefore, we developed different electronic devices which require either ohmic or blocking contacts or both. We evaluated the domin...

Single ZnO nanowires prepared by wet and dry methods are used as channels in high performance back-gated field effect transistors working in low power operation mode, with on-off ratios up to 10 and mobilities up to 167 cm V s. The nanowires' properties, generated by the growth techniques, influence the parameters of the transistors, therefore a throughout comparison is made.

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Indium tin oxide (ITO) thin films were grown on nanopatterned glass substrates by the pulsed laser deposition (PLD) technique. The deposition was carried out at 1.2 J/cm2 laser fluence, low oxygen pressure (1.5 Pa) and on unheated substrate. Arrays of periodic pillars with widths of ~350 nm, heights of ~250 nm, and separation pitches of ~1100 nm were fabricated on glass substrates using UV nanoimprint lithography (UV-NIL), a simple, cost-effective, and high throughput technique used to fabricate nanopatterns on large areas. In order to emphasize the influence of the periodic patterns on the properties of the nanostructured ITO films, this transparent conductive oxide (TCO) was also grown on flat glass substrates. Therefore, the structural, compositional, morphological, optical, and electrical properties of both non-patterned and patterned ITO films were investigated in a comparative manner. The energy dispersive X-ray analysis (EDX) confirms that the ITO films preserve the In2O3:SnO2 weight ratio from the solid ITO target. The SEM and atomic force microscopy (AFM) images prove that the deposited ITO films retain the pattern of the glass substrates. The optical investigations reveal that patterned ITO films present a good optical transmittance. The electrical measurements show that both the non-patterned and patterned ITO films are characterized by a low electrical resistivity (<2.8 × 10−4). However, an improvement in the Hall mobility was achieved in the case of the nanopatterned ITO films, evidencing the potential applications of such nanopatterned TCO films obtained by PLD in photovoltaic and light emitting devices.

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 photodetector device was evaluated by assessing its key parameters: responsivity, external quantum efficiency and detectivity. The results highlighted that the obtained CuO–ZnO core–shell nanowires are emerging as potential building blocks for a next generation of photodetector devices.

Ferroelectric field effect transistors (FeFETs) based on lead zirconate titanate (PZT) ferroelectric material and amorphous-indium-gallium-zinc oxide (a-IGZO) were developed and characterized. The PZT material was processed by a sol-gel method and then used as ferroelectric gate. The a-IGZO thin films, having the role of channel semiconductor, were deposited by radio-frequency magnetron sputtering, at a temperature of ∼50 • C. Characteristics of a typical field effect transistor with SiO 2 gate insulator, grown on highly doped silicon, and of the PZT-based FeFET were compared. It was proven that the FeFETs had promising performances in terms of I on /I off ratio (i.e., 10 6) and I DS retention behavior.