Fabrication of metallic contacts to nanometre-sized materials using a focused ion beam (FIB)

Nanometre-sized materials, like nanowires, nanoparticles or nanobelts, are gaining huge interest as building blocks of modem electronic nanodevices. Their fabrication feasibility has been demonstrated in the last years, and different routes are already well established in order to synthesize these materials. However, the assessment of their electrical properties is still a challenging issue, due to the difficulty to perform a precise nanolithography process allowing the access to such small structures. The fabrication of metallic contacts with precision in the nanometre range is necessary, as well as achieving a flexible system that allows to contact individual structures. Such a system could be a dual-beam Focused Ion Beam instrument, which combines Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) in one machine, able to assist deposition of materials with nanometre precision. In this work, the methodology of fabrication of metallic nanocontacts to access different nanometre-sized materials inside a dual-beam FIB instrument is presented. Both electron and ion-beam assisted deposition are used and advantages of one or the other primary beams are discussed as a function of the material to be contacted and of the field in which such material will be further employed. The resulting electrical properties are presented and the influence of the contacting method is discussed. Finally, the complete fabrication process of nanodevices is illustrated in the case of metal-oxide nanowires showing gas sensing capabilities, which have been contacted using a dual-beam FIB machine. Their gas response is presented and the possibility of using this method in future technologies is briefly discussed. (c) 2005 Elsevier B.V. All rights reserved.