Direct formation of catalyst-free ZnO nanobridge devices on an etched Si substrate using a thermal evaporation method.

Well-aligned single crystalline ZnO nanobridges have been synthesized selectively across the prefabricated electrodes on silicon substrates by a single-step thermal evaporation method without using any metal catalysts or a predeposited ZnO seed layer that was a prerequisite for such synthesis. The growth region was self-defined by the anisotropic surface of the silicon substrate as initially postulated. Careful control of the reaction time and the substrate temperature allows the nanobridges to form almost exclusively across the electrodes. The photoresponses as well as the current-voltage characteristics of the device confirm that this single-step process indeed offers a simple and a cost-effective way to integrate self-assembled nanodevices based on individual and/or a large number of ZnO nanowires with conventional circuits without using e-beam lithography techniques and/or additional costly deposition processes.