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 μC cm−2, unprecedented in single-step charge-based nanopatterning). This resist-free process consists in the condensation of a ∼28 nm-thick Co2(CO)8 layer on a substrate held at −100 °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 μΩ 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 × 103 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.This project was supported by the Spanish Ministry of Science through the grant numbers PID2019-105881RB-I00, MAT2017-82970-C2-2-R and PID2020-112914RB-I00, including FEDER funding, from CSIC through projects PIE202060E187 and Research Platform PTI-001, and by Gobierno de Aragón through the grant number E31_20R with European Social Fund (Construyendo Europa desde Aragón). P. P. is grateful to the National Research Fund (FNR), Luxembourg (C17/MS/11682850/ULOWBEAM). M. V. K gratefully acknowledges funding from Swedish energy agency-Energimyndigheten (48698–1) and Swedish Research Council Formas (Grant no. 2019–01326). The following networking projects are acknowledged: Spanish Nanolito (MAT2018-102627-T) and COST-FIT4NANO (action CA19140). We thank preliminary tests and discussions with the master student Camilo Sánchez Velasquez (University of Zaragoza) and with Dr Pablo Orus (INMA). We acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza. Technical support by the LMA technicians at Universidad de Zaragoza is acknowledged.Peer reviewe