Nanoscale, surface-confined phase separation by electron beam induced oxidation.

Electron-assisted oxidation of Co-Si-based focused electron beam induced deposition (FEBID) materials is shown to form a 2-4 nm metal oxide surface layer on top of an electrically insulating silicon oxide layer less than 10 nm thick. Differences between thermal and electron-induced oxidation on the resulting microstructure are illustrated.

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

The investigation of precursor classes for the fabrication of nanostructures is of specific interest for maskless fabrication and direct nanoprinting. In this study, the differences in material composition depending on the employed process are illustrated for focused-ion-beam- and focused-electron-beam-induced deposition (FIBID/FEBID) and compared to the thermal decomposition in chemical vapor deposition (CVD). This article reports on specific differences in the deposit composition and microstructure when the (H3Si)2Fe(CO)4 precursor is converted into an inorganic material. Maximum metal/metalloid contents of up to 90 at. % are obtained in FIBID deposits and higher than 90 at. % in CVD films, while FEBID with the same precursor provides material containing less than 45 at. % total metal/metalloid content. Moreover, the Fe:Si ratio is retained well in FEBID and CVD processes, but FIBID using Ga+ ions liberates more than 50% of the initial Si provided by the precursor. This suggests that precursors for FIBID processes targeting binary materials should include multiple bonding such as bridging positions for nonmetals. In addition, an in situ method for investigations of supporting thermal effects of precursor fragmentation during the direct-writing processes is presented, and the applicability of the precursor for nanoscale 3D FEBID writing is demonstrated.

Hybrid core-shell nanoparticles for cell-specific magnetic separation and photothermal heating.

Hyperthermia, as the process of heating a malignant site above 42 °C to trigger cell death, has emerged as an effective and selective cancer therapy strategy. Various modalities of hyperthermia have been proposed, among which magnetic and photothermal hyperthermia are known to benefit from the use of nanomaterials. In this context, we introduce herein a hybrid colloidal nanostructure comprising plasmonic gold nanorods (AuNRs) covered by a silica shell, onto which iron oxide nanoparticles (IONPs) are subsequently grown. The resulting hybrid nanostructures are responsive to both external magnetic fields and near-infrared irradiation. As a result, they can be applied for the targeted magnetic separation of selected cell populations - upon targeting by antibody functionalization - as well as for photothermal heating. Through this combined functionality, the therapeutic effect of photothermal heating can be enhanced. We demonstrate both the fabrication of the hybrid system and its application for targeted photothermal hyperthermia of human glioblastoma cells.

Mixed-Substituted Single-Source Precursors for Si1-xGex Thin Film Deposition.

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-xGex coatings. Moreover, partial crystallization of the Si1-xGex 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.

Vanadium and Manganese Carbonyls as Precursors in Electron-Induced and Thermal Deposition Processes.

The material composition and electrical properties of nanostructures obtained from focused electron beam-induced deposition (FEBID) using manganese and vanadium carbonyl precursors have been investigated. The composition of the FEBID deposits has been compared with thin films derived by the thermal decomposition of the same precursors in chemical vapor deposition (CVD). FEBID of V(CO)6 gives access to a material with a V/C ratio of 0.63-0.86, while in CVD a lower carbon content with V/C ratios of 1.1-1.3 is obtained. Microstructural characterization reveals for V-based materials derived from both deposition techniques crystallites of a cubic phase that can be associated with VC1-xOx. In addition, the electrical transport measurements of direct-write VC1-xOx show moderate resistivity values of 0.8-1.2 × 103 µΩ·cm, a negligible influence of contact resistances and signatures of a granular metal in the temperature-dependent conductivity. Mn-based deposits obtained from Mn2(CO)10 contain ~40 at% Mn for FEBID and a slightly higher metal percentage for CVD. Exclusively insulating material has been observed in FEBID deposits as deduced from electrical conductivity measurements. In addition, strong tendencies for postgrowth oxidation have to be considered.

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.

Aerosol-assisted CVD of thioether-functionalised indium aminoalkoxides.

ABSTRACT: Thioether-functionalised indium aminoalcoholates have been used as single-source precursors in aerosol-assisted CVD processes. The obtained In2O3-x S x oxysulphide deposits show either a single indium sulphide phase for deposits with high sulphide content [>75% (S/(S + O)) for the t-butyl derivatives] or pronounced phase separation in indium oxide and indium sulphide for lower sulphide content [<62% (S/(S + O)) for the n-butyl derivatives]. In addition to thin films, polycrystalline 1D structures are obtained at slightly modified synthesis conditions. The materials are analysed by EDX, XRD, XPS, SEM, and TEM.