Focused Ion Beam vs Focused Electron Beam Deposition of Cobalt Silicide Nanostructures Using Single-Source Precursors: Implications for Nanoelectronic Gates, Interconnects, and Spintronics

Abstract

Direct-write techniques for the fabrication of nanostructures are of specific interest due to their ability for a maskless fabrication of any arbitrary three-dimensional shape. To date, there is a very limited number of reports describing differences in the focused ion and electron beam induced deposition (FIBID/FEBID) for the same precursor species. This report contributes to filling this gap by testing two single-source precursors for the deposition of cobalt silicide in Ga-ion beam writing and reveals H 2 Si(Co-(CO) 4 ) 2 to be a very suitable precursor for the technique retaining the 2:1 ratio of Co:Si in the deposit. Maximum metal/metalloid contents of up to 90 atom % are obtained in FIBID deposits, while FEBID with the same precursor provides material containing <60 atom % total metal/metalloid content. A dense deposit is obtained by using FEBID showing paramagnetic behavior and electric properties of a granular metal. In contrast, the FIBID material is porous and the expected ferromagnetic and temperature-dependent electric properties for dicobalt silicide have been observed. Further analysis enabled the proposition of different dominating material conversion channels based on the observed microstructural features including bubble formation in FIBID-derived material. The differences in materials properties depending on the deposition strategy can influence the cobalt silicide deposits' applicability in nanoelectronics and spintronics.

Gas-Phase Synthesis of Iron Silicide Nanostructures Using a Single-Source Precursor: Comparing Direct-Write Processing and Thermal Conversion

“…Moreover, similar surface science studies have demonstrated that ion bombardment of condensed precursor layers results in films with a much higher metal content, when compared to pure electron irradiation. , In addition, the studies do not describe a preferential sputtering of either metal in bimetallic CpFe­(CO) 2 Re­(CO) 5 by Ar + ion bombardment of condensed precursor films but rather C 5 FeRu layer formation with carbonyls being liberated efficiently . This is in line with FIBID of a 2:1 Co:Si metal/metalloid ratio from H 2 Si­(Co­(CO) 4 ) 2 . In contrast, H 3 SiCo­(CO) 4 -derived FIBID material revealed significant Si loss, while FEBID material retained the metal/metalloid ratio, which was attributed to increasing impact of sputtering effects in FIBID due to low growth rates. , …”

“…It should be noted that the lowest resistivity values for other FIBID deposits derived by Ga + ions based on Pt (∼800 μΩ·cm), Pd (∼1000 μΩ·cm), Co 2 Si (∼330 μΩ·cm), and W (∼200 μΩ·cm) , typically are fairly high when compared to those of pure metals. Exceptions are the higher-purity Cu (∼50 μΩ·cm) and Co-based (∼20 μΩ·cm) FIBID material, but significant differences have been observed depending on compositional changes and postgrowth processing.…”

“…Similar observations have been made for H 3 SiCo­(CO) 4 , where significant Si loss has been reported. In contrast to these two precursors with terminally bonded SiH 3 moieties, H 2 Si­(Co­(CO) 4 ) 2 owning a bridging silyl retains most of the Si and is less prone to sputtering effects, which could be related to either a higher growth rate or the bonding situation of the Si . This could indicate a general predicament of precursor design requiring multiple bonding of lighter elements in single-source precursors for binary materials in order to retain these elements in the ion-induced deposition.…”

“…37 This is in line with FIBID of a 2:1 Co:Si metal/metalloid ratio from H 2 Si(Co-(CO) 4 ) 2 . 38 In contrast, H 3 SiCo(CO) 4 -derived FIBID material revealed significant Si loss, while FEBID material retained the metal/metalloid ratio, which was attributed to increasing impact of sputtering effects in FIBID due to low growth rates. 38,39 In the past, FIBID fragmentation was attributed to a thermal spike model or a binary collision model.…”

Formation of negative ions from cobalt tricarbonyl nitrosyl Co(CO)3NO clusters

“…The Focused Electron Beam-Induced Deposition (FEBID) method [1][2][3][4] is increasingly employed to deposit various layers and 3D structures at the nanoscale. [5][6][7][8][9] In FEBID, a high-energy electron beam is used to induce the decomposition of precursor gases, leading to the deposition of the metal component from the precursor onto the surface. 1,2,4 Various types of precursors have been utilized in FEBID, including W(CO) 6 , Et 4 Pb, Fe(CO) 5 , Fe 2 (CO) 9 , Co 2 (CO) 8 , HCo 3 Fe(CO) 12 , AgO 2 Me 2 Bu and many others.…”