Direct Writing of Cobalt Silicide Nanostructures Using Single-Source Precursors

Two new precursors for focused electron beam-induced deposition (FEBID) of cobalt silicides have been synthesized and evaluated. The H₃SiCo(CO)₄ and H₂Si(Co(CO)₄)₂ single-source precursors retain the initial metal ratios and show low sensitivity to changes in the FEBID parameters such as acceleration voltage, beam current, and precursor pressure. The precursors allow the direct writing of material containing ∼55 to 60 at % total metal/metalloid content combined with high growth rates. During the deposition process an average of ∼80% of the carbonyl ligands are cleaved off in these planar deposits. Postgrowth electron curing does not change the deposits' composition, but resistivities decrease after the curing procedure. Temperature-dependent electrical properties indicate the presence of a granular metal for both cured samples and the as-grown Co₂Si deposit, while the as-grown CoSi material is on the insulating side of the metal-insulator transition. The observed magnetoresistance behavior is indicative of tunneling magnetoresistance and is substantially reduced upon postgrowth irradiation treatment.