Electrical properties of single CuO nanowires for device fabrication: Diodes and field effect transistors

Abstract

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...

Defect-concentration dependence of electrical transport mechanisms in CuO nanowires

“…21 Florica et al discovered that NNH dominates at low temperatures, compared with thermal activation at high temperatures. 19 The results of these two studies differ signicantly from each other, and statistically signicant results are lacking. Thus, more detailed studies of the transport mechanisms are needed to discover the reasons for these differences and to pinpoint the factors that determine the actual transport mechanisms.…”

“…Some reports have indeed pointed out that the inuence of the contact resistance on the value of the activation energy is negligible. 19 Fig . 4 shows the three typical types of temperaturedependent I-V characteristics.…”

“…Proposed transport mechanisms include defect-induced thermal activation, variable-range hopping, nearest-neighbor hopping (NNH), and space-chargelimited currents (SCLC). 11,12,[17][18][19][20][21] Further, most of these studies have focused on n-type nanowires, with only a few dealing with p-type nanowires, which enable complementary devices.…”

Surface‐enhanced Raman scattering characteristics of CuO : Mn/Ag heterojunction probed by methyl orange: effect of Mn2+ doping

“…The Fermi level of Ag is situated at À5.5 eV (vacuum), and the one of CuO is at À5.3 eV (vacuum). [48,49] On the adsorption of CuO (or Mn-doped CuO) nanoparticles onto the surface of nanostructured Ag island film, it can be assumed predominantly that the Fermi level of the CuO : Mn/Ag heterojunction will exist between the Fermi levels of Ag and CuO (or Mn-doped CuO). When MO is adsorbed onto the CuO : Mn/Ag heterojunction surface and the resulting CuO : Mn/Ag + MO complex is irradiated by excitation source used for Raman, then a photon-induced CT phenomenon takes place, and the charge is transferred from the Fermi level of CuO : Mn/Ag heterojunction to the HOMO level of MO.…”

Photodetecting properties of single CuO–ZnO core–shell nanowires with p–n radial heterojunction

“…Copper oxide (CuO) is a p-type semiconductor with a narrow band gap in the range of 1.2–2.1 eV 23 , and high optical absorption in the visible range. It is also highly versatile and easy to prepare material, suitable for applications in field effect transistors 24 , photodetectors 25 , light emitting diodes 26 , solar cells 27 , photocatalysis 28 , etc. Zinc oxide (ZnO) is a n-type semiconductor with a wide band gap (3.37 eV), a 60 meV exciton binding energy 29 .…”