A Route to Fabricate Nanocontacts by X-ray Lithography for the Realization of Single Electron Transistors and Highly Sensitive Biosensors

The fabrication of single electron transistors and/or highly sensitive biosensors is still a challenging task on account of the tight control required to get proper shapes and size of the electrodes. The nanosized tips and the separation of a few nanometers between electrode pairs are critical features. Conventional lithography is not suited to obtain these features because of the resolution limits, so that previous alternative approaches have involved the use of electron beam lithography, focused ion beam lithography or scanning probe nanolithography. The novel approach presented in this letter is the exploitation of X-ray lithography in the Elettra synchrotron to fabricate arrays of nanocontacts spaced a few nanometers, devoted to the design of a new class of nanodevices based on nanoparticles and/or single molecules, including single electron transistors and highly sensitive biosensors. The method to fabricate such devices is illustrated and discussed. Experimental details of the fabrication process are given and preliminary results are presented through SEM and AFM images. It is worth noting that this paper presents a viable method to produce nanocontacts by using the X-ray lithography by synchrotron radiation source, that has not yet been reported together with experimental, though preliminary, data.