Fabrication of Electrical Nanocontacts to Nanometer-sized materials and Structures Using a Focused Ion Beam
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Fabrication of Electrical Nanocontacts to Nanometer-sized materials and Structures Using a Focused Ion Beam F.Hernández-Ramírez1, O.Casals1, J.Rodríguez1, A.Vilà1, A.Romano-Rodríguez1, J.R.Morante1, M.Abid2 and S.Valizadeh3, 1 Department of Electronics, University of Barcelona, Martí i Franquès 1, E-08028, Barcelona, Spain, 2 Ångströmlaboratoriet, Universitet Uppsala, Lägerhyddsvägen 1, SE-751 21 Uppsala, Sweden, 3 Laboratoire de Physique des Matériaux Nanostructurés, École Polytechnique Fédérale de Lausanne, EPFL, CH-1015 Lausanne, Switzerland ABSTRACT A Dual Beam Focused Ion Beam (FIB) machine has been used to deposit platinum contacts on different nanostructured materials using both electron- and ion-assisted deposition. The electrical quality of the deposited platinum has been studied, and the feasibility of using this nanofabrication method to extract electrical parameters of nanomaterials demonstrated. The advantage of combining electron- and ion-assisted deposition instead of using only ion-assisted deposition is discussed. The possibility of applying this method in the fabrication of future nanodevices is demonstrated in a gas nanosensor prototype. INTRODUCTION Fabrication of electrical contacts on nanometer-sized materials is the key to determine their electrical parameters and for their future device application [1]. Focused Ion Beam (FIB) ionassisted deposition has been used in the past as an alternative to electron-beam lithography due to the possibility of contacting a desired nanostructure in a direct (no need of masks), simpler and faster way [2-3]. Nevertheless, the surface damage and structure modification introduced by ion bombardment (Ga+ ions accelerated to 30kV, in our case) have restrained the use of this technique. Some groups have attempted to fabricate electrical contacts by using low ion currents in the proximity of the nanomaterials in order to reduce the damage. However, ion exposure is not eliminated and contacted nanomaterials are modified [3-4]. The appearance of the so-called Dual Beam systems (a conventional FIB microscope combined with a Scanning Electron Microscope (SEM)) opens the possibility of using both ion- and electrical-assisted deposition. Due to the fact that interaction between electrons and sample is less destructive, performing an electron-assisted deposition on the nanostructure to be contacted and finishing the rest of the contact with the help of ions can avoid undesired surface damage and structure modification of the nanostructure. In this work, nanowires (NWs) and nanoparticles (NPs) contacted to microelectrodes in 2- and 4-probe configurations, following the procedure of combining both electron- and ion-assisted deposition, are presented. The quality of the deposited platinum and contacts has been evaluated as a function of their dimensions, chemical composition, current density through them and time. We have also studied the electrical response of some of the contacted NWs and NPs, demonstrating the possibility of extracting their electrical parameters.
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