Nanowire Nanoarray Memories

About

Technology Methods have been developed for growing nanowires (NWs) and carbon nanotubes (NTs) with diameters of a few nanometers and for assembling NWs into nanoarrays, crossbars containing two orthogonal sets of parallel wires on either side of a molecular layer.  Molecules in the molecular layer are chosen that change their conductivity under the application of large positive and negative electric fields.  The state of a switch at a crosspoint can be sensed without changing its state by application of a smaller electric field.  Such ‘nanocrossbars’ have the potential to serve as very high density memories and programmed logic arrays (PLAs).  To read and store data in nanoarrays requires individual NWs be addressable (possible to select one NW from each orthogonal set of NWs and apply a voltage to or pass a current through it).  To control NWs from the lithographic level requires that mesoscale wires (MWs) be used to address NWs.  However, if each NW is connected to a single MW, the close packing possible with NWs is lost.  Therefore, schemes/decoders that use multiple MWs to control individual NWs have been proposed, and all assume that MWs are placed at right angles to NWs.  The need for an effective method of differentiating NWs is apparent due to the problems that arise with axially encoded NWs as a result of their random misalignment during fluidic assembly of crossbars. This invention is an apparatus, method and computer program product providing radial addressing of nanowires.  This novel method constructs a device that includes a plurality of nanowires (NWs), each with a core and at least one shell.  The method includes providing a plurality of radially encoded NWs where each shell contains one of a plurality of different shell materials.  Selectively removing, or not, shell material within areas to be electrically coupled to individuals in a plurality of mesowires (MWs) differentiates individual NWs.  The method also encompasses a nanowire array (1, 2, or 3-dimensions) containing radially encoded NWs and a computer program product useful in forming a nanowire array.  This new method has the advantage of being less sensitive to the random displacements produced by stochastic assembly.  Radial codes are easier to manufacture than conventional axial encoders, do not have an ambiguous activation state, and do not suffer from misalignment errors between doped and undoped regions, characteristic of conventional NWs.  Thus, radial coding is an attractive method to differentiate NWs when they are assembled into crossbars. Applications are in creating cross bar switches used in memory elements and programmable logic arrays (PLSs).  The invention is implemented in/by hardware, software, special purpose circuits, firmware, controller or other general hardware, and/or logic. The arrays can be applied in the detection of biological molecules.  Markets include: computer software/hardware; pharmaceutical and environmental - diagnostics/detection and/or medical devices; scientific R&D to advance the fields of material sciences, computer science, bioengineering/biochemical engineering, and nanotechnology/engineering.