Although optical lithography is suited for producing intricate architectures,its combination with'bottom-up'approaches becomes a very challenging issue.The challenge is to electrically address the coordinates of millions of nanoparticles(e.g.,nanowires)on a given surface.Here,we describe a method that controls the registries of horizontally grown nanowires(NWs)and advances the current state-of-the-art NW device assembly technology.In this architecture,NWs are grown where the nanodevices will later be fabricated on.There is no need to transfer NWs to a different surface or align them.With the use of only three photolithographic steps,this technique allows industrial-scale production of nanodevices.First,an alpha-plane sapphire surface is patterned with gold nanodroplets.Next,small-diameter zinc oxide NWs are grown selectively on the predefined gold sites.Growth direction of the NW is controlled using the anisotropic crystal match between zinc oxide and the underlying substrate.Subsequently,metal electrodes are deposited on NWs at once and in a parallel fashion.To demonstrate the capabilities of this method,large numbers of top-gated zinc oxide NW field-effect transistors are prepared using optical lithography.This fabrication method opens the path to a new generation of nonconventional nanodevices and nanosensors and could impact nanotechnology industries.
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