ZnO Nanobelt/Nanowire Schottky Diodes Formed by Dielectrophoresis Alignment across Au Electrodes

Abstract

Rectifying diodes of single nanobelt/nanowire-based devices have been fabricated by aligning single ZnO nanobelts/nanowires across paired Au electrodes using dielectrophoresis. A current of 0.5 µA at 1.5 V forward bias has been received, and the diode can bear an applied voltage of up to 10 V. The ideality factor of the diode is ∼3, and the on-to-off current ratio is as high as 2000. The detailed IV characteristics of the Schottky diodes have been investigated at low temperatures. The formation of the Schottky diodes is suggested due to the asymmetric contacts formed in the dielectrophoresis aligning process.Zinc oxide is an important optical and optoelectronic material. Recently, utilizing its unique crystal structure and the three major fastest growth directions, various singlecrystal/crystalline nanostructures of ZnO have been synthesized, such as nanobelts, 1 nanorings, 2 and nanohelices. 3 From the abundance of the surface morphologies, ZnO offers the most diverse nanostructure of any material known today. With a large direct band gap of 3.37 eV, together with its piezoelectricity and pyroelectricity, ZnO is most attractive for applications as a field-effect transistor (FET) 4 or sensor 5 and in optical electronics. 6 Extensive research on the electronic properties of various one-dimensional nanostructures has been performed. [7][8][9][10] To apply ZnO nanostructures on various electronic devices, it is important for one to understand its transport properties and its interaction with metal contacts. In this letter, we investigated the contact of a single ZnO nanobelt with gold electrodes. After investigating the transport properties of over 60 single nanobelt-based circuits, we found a spontaneous formation of a Au/ZnO nanobelt Schottky diode in 80% of the samples when nanobelt sizes are well controlled. This effect is likely due to the nonsymmetric contacts at the two ends of the nanobelt.The ZnO nanobelts to be used for fabricating the FET devices were synthesized through a solid-vapor process in a high-temperature horizontal furnace system. 1 The Au electrode patterns were defined with photolithography on a SiO 2 substrate. The electrodes consisted of two 3-µm-wide fingers pointed head to head at a distance of 4 µm. These two fingers are connected to two 500 × 500 µm 2 contacting pads for probe contacts. The as-synthesized nanobelt samples were placed in ethanol and ultrasonicated for 15 min to disperse the bundles into individual nanobelts. A single nanobelt is "placed" across the prefabricated electrodes using the dielectrophoresis technique. 11 After applying a droplet of the nanobelt suspension onto the electrodes, the electrodes were connected to a 5 V and 1 MHz AC signal, which was chosen for optimizing the alignment of a single nanobelt. This signal generated an alternating electrostatic force on the nanobelts in the solution. Under the electrical polarization force, the nanobelts were deposited on the electrodes. By precisely controlling the concentration of the nanobelt in the solution, ...

Synthesis and Electrical Transport of Single-Crystal NH4V3O8 Nanobelts

“…The fabrication of a single NH 4 V 3 O 8 nanobelt-based device was carried out by ac electrophoresis. 19 …”

Interface trap characterization and electrical properties of Au-ZnO nanorod Schottky diodes by conductance and capacitance methods

“…4 In recent years, a number of process methodologies have been developed for the fabrication of reproducible high quality Schottky contacts on ZnO nanostructures, but controversies remain with regard to the Schottky barrier height and the ideality factor of the ZnO Schottky contacts. 2,[8][9][10][11] The deviations in the barrier heights and the ideality factor have been proposed as having been caused by the effects of asymmetric contacts, and the influence of the interfacial layers and/or surface states. [9][10][11][12] In fact, the surfaces of nanostructures should mostly be dominated by surface states because abundant surface states usually exist on the surfaces of these nanostructures.…”

“…2,[8][9][10][11] The deviations in the barrier heights and the ideality factor have been proposed as having been caused by the effects of asymmetric contacts, and the influence of the interfacial layers and/or surface states. [9][10][11][12] In fact, the surfaces of nanostructures should mostly be dominated by surface states because abundant surface states usually exist on the surfaces of these nanostructures. 13 However, to the best of our knowledge, there have been few reports on Schottky contacts on ZnO nanostructures, and no previous report has been found that illustrates the influence of the surface states on the barrier potential and rectifying behavior of ZnO nanostructure Schottky diodes.…”

Piezoelectricity in ZnO nanowires: A first-principles study

“…Room-temperature ultraviolet lasing [12] and piezoelectric nanogenerators based on ZnO nanowire arrays have been demonstrated [13]. Rectifying diodes of single ZnO nanobelt/nanowire-based devices [14] and a ZnO nanowire photodetector [15] were fabricated very recently.…”