Highly-efficient growth of cobalt nanostructures using focused ion beam induced deposition under cryogenic conditions : application to electrical contacts on graphene, magnetism and hard masking

Emergent technologies are required in the field of nanoelectronics for improved contacts and interconnects at nano and micro-scale. In this work, we report a highly-efficient nanolithography process for the growth of cobalt nanostructures requiring an ultra-low charge dose (15 mu C cm(-2), unprecedented in single-step charge-based nanopatterning). This resist-free process consists in the condensation of a similar to 28 nm-thick Co-2(CO)(8) layer on a substrate held at -100 degrees C, its irradiation with a Ga+ focused ion beam, and substrate heating up to room temperature. The resulting cobalt-based deposits exhibit sub-100 nm lateral resolution, display metallic behaviour (room-temperature resistivity of 200 mu omega cm), present ferromagnetic properties (magnetization at room temperature of 400 emu cm(-3)) and can be grown in large areas. To put these results in perspective, similar properties can be achieved by room-temperature focused ion beam induced deposition and the same precursor only if a 2 x 10(3) times higher charge dose is used. We demonstrate the application of such an ultra-fast growth process to directly create electrical contacts onto graphene ribbons, opening the route for a broad application of this technology to any 2D material. In addition, the application of these cryo-deposits for hard masking is demonstrated, confirming its structural functionality