Nanotechnology is today mainly focused on the realization of nanodevices. The attempt is to build self-consistent components with two contacting pads at least. These devices are regarded as the direct evolutions of many proofs of principles making use of Scanning Tunneling Microscope (STM) tips as one electrode and sample substrates as the second electrode.
A solution can be the utilization of flexible plastic sheets with evaporated metal wires, bended in order to break the lines and to realize small gaps, suitable for further experiments with different molecules.
Another approach makes use of lithography processes to build directly the desired nanostructures. This contribution belongs to the latter group.
Our fabrication process involves the Electron Beam Lithography (EBL) technique to define metallic microstructures onto which nanometer scale patterning is performed using an Atomic Force Microscope (AFM) as a mechanical modification tool.
Both direct and indirect AFM lithography are applied in order to achieve the smallest possible separation between electrode pairs. In the first, direct, case the AFM tip in contact with the sample scratches a metal strip thus producing wells of defined geometrical size. When the scratches are realized in the near proximity of a thin metal region, it is possible to create nanometer-size gaps, suitable for the development of quantum effect devices. In the second case upper sacrificial layers are properly added to the underlying sample. The AFM is used to scratch these layers, forming a mask, which is used for a subsequent etching process, by means of which a pattern transfer to the underlying metal structures occurs.
We have developed a fabrication technique showing good reproducibilty and operation control during the lithographic process, both ensured by the imaging facilities of the AFM. This can be considered as a reliable starting point for the development of nano-electronic devices, such as Single Electron Transistors (SET).
In addition, this contribution shows several results achieved with a molecular conductance study and a morphological caracterization of electrode pairs separated by nanometer gaps.