Bi-directional porous alumina wire templates for nanowire field-effect transistors
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Bi-directional porous alumina wire templates for nanowire field-effect transistors Travis L. Wade, Xavier Hoffer, Jean-François Dayen, Al Dughaim Mohammed, Fahad Humel, and Jean-Eric Wegrowe Laboratoires des Solides Irradiés ECOLE Polytechnique 91128 Palaiseau France ABSTRACT Using readily available materials and equipment we are able to sculpture aluminium wires into cylindrical, bi-directional templates for the synthesis and contacting of nanowires as fieldeffect transistors. The nanowire template is made by partial anodization of the wire perpendicular to its axis as an isolating layer for a gate electrode, vapour deposition of a metal on this layer as a gate, cutting the wire perpendicular to its axis, and finally anodizing the newly exposed area parallel to the wire axis as a template for nanowires. This results in a nanowire template surrounded by a gate electrode that is isolated from the template by the first anodisation layer. The utility of this structure is demonstrated by a ZnO nanowire field-effect transistor. The ZnO was made by electrodeposition of Zn nanowires in the interior nanoporous template during which an anodic pulse was applied to form a layer of ZnO in the middle of the zinc nanowires. The IV and transfer plots indicate that the ZnO is p-type in depletion mode. This 3-D transistor is unique in that it can be totally fabricated in a beaker without the need for costly clean room and lithography facilities. The ease and low cost of this new approach to nanodevices will have the effect of liberating nanoscience for scientists of moderate means. As a result this will open nanoscience to new ideas and more inputs. INTRODUCTION There are many elegant chemical and physical routes to nanowires and nanodots. Electrodeposition, sol-gel synthesis, and CVD are but a few of the techniques that can produce nanostructures with nanometer control.[1-4] The quality and reproducibility of these nanostructures are well developed. The real trick, however, is to organise and contact these nano-objects.[5, 6] This is where a template comes into play. The role of the template is two fold. First, it allows the reproduction of the structure with the best possible reproducibility and it plays the role of a skeleton in order to organize the different functions of a device, the active components and the different interfaces (building blocks, electric contacts, gate voltage, bias fields, optical sensors…) on a rigid body. For example, the role of the template is to allow the manipulation of the building blocks without the need of a microscopic tip (no systematic use of AFM or STM) or without the need of top-down processes (lithography, FIB, lift-off). Second, it is used to link the structure to the macroscopic word, i.e. the contacts. In the scheme of template synthesis it is possible to identify three different steps: (1) the creation of the building blocks, (2) the assembly of the building blocks into a functional architecture within the template, and (3) the fabrication and control of the contact to the
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