Focused electron beam-induced deposition (FEBID) is a maskless, direct-write nanolithography approach for the growth of nanostructures. In recent years, significant progress has been made demonstrating highly controlled writing processes with...
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.
Mixed-metal carbonyls are a family of compounds which can be used to fabricate bimetallic nanostructures by means of focused electron beam induced deposition. In the present work, we show that silicon-metal alloys can be prepared by using silyl-metal carbonyls. In particular, we employ the SiH 3 Mn(CO) 5 precursor to fabricate Mn-Si alloy nanowires, with composition of about 34 at% Mn, 17 at% Si, 31 at% C and 18 at% O, as revealed by energy dispersive x-ray analysis. Magnetotransport measurements are carried out on as-grown samples and on samples treated after-growth by low-energy electron irradiation. All the samples exhibit a quasimetallic temperature-dependent behavior. Hall-effect measurements indicate either electronlike transport, for as-grown samples, or hole-like transport, for post-growth treated samples, respectively. Correspondingly, the charge carrier density increases from n ≈ 10 20 cm −3 to n ≈ 10 22 cm −3 . We find a small negative transversal magnetoresistance, which depends on irradiation dose and temperature. Microstructural investigations carried out by transmission electron microscopy indicate that the samples are constituted by an amorphous Mn 2 Si phase embedded in a carbonaceous matrix. Additionally, in treated samples a novel Mn 2 SiO 4 spinel oxide phase is observed.
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.
A series of new mixed-substituted heteronuclear precursors with preformed Si–Ge bonds has been synthesized via a two-step synthesis protocol. The molecular sources combine convenient handling with sufficient thermal lability to provide access to group IV alloys with low carbon content. Differences in the molecule–material conversion by chemical vapor deposition (CVD) techniques are described and traced back to the molecular design. This study illustrates the possibility of tailoring the physical and chemical properties of single-source precursors for their application in the CVD of Si1–x Ge x coatings. Moreover, partial crystallization of the Si1–x Ge x has been achieved by Ga metal-supported CVD growth, which demonstrated the potential of the presented precursor class for the synthesis of crystalline group IV alloys.
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