Preparation of Iron and Gold Silicide Nanodomains on Silicon (111) by the Reaction of Gold, Iron−Gold Core−Shell, and Alloy Nanoparticles with Triethylsilane

Abstract

This study describes a strategy to use composite colloidal nanoparticles and triethylsilane as precursors to synthesize nanometer size structures on single-crystal silicon substrate. The concept is demonstrated by depositing gold, iron-gold alloy, and iron-gold core-shell nanoparticles on silicon (111). Upon heating, the nanoparticles form new crystalline phases on the Si (111) surface. Atomic force microscope (AFM) data show the collapse of the iron gold core-shell and alloy nanoparticles at temperatures 100-200 degrees C higher than gold nanoparticles, indicating the efficient tethering of iron containing nanoparticles on silicon (111). Both structural analysis and X-ray spectroscopy show that the iron-gold alloy and iron-gold core-shell nanoparticles successfully form the semiconducting beta-FeSi(2) phase at relatively low temperature. The stabilities of the silicide are assessed at elevated temperatures. Silicon successfully nucleates on the created nanostructures, which suggests strong catalytic activity towards producing further nanostructures on the surface.

Coexistence of plasmonic and magnetic properties in Au89Fe11 nanoalloys

“…3B, the calculated spectrum (black line) agrees well with the experimental one, reproducing both damping and the blue shi of the surface plasmon resonance. This result also suggests that previous reports on red-shied plasmon resonance in Au-Fe alloy nanoparticles 34,35,39,40,64 are likely due to samples with heterogeneous composition or to particle aggregation.…”

“…22 At the nanoscale, the attempts to synthesize gold-iron alloy nanoparticles on substrates or in solution have been limited so far. AuFe alloy nanoparticles (AuFeNPs) were obtained by sequential ion implantation of iron in AuNPs embedded in a silica matrix, 15,31,32 by simultaneous reduction of Au salts and decomposition of Fe compounds in the presence of capping molecules dissolved in liquid solutions, [33][34][35][36][37][38][39][40][41][42] by electrodeposition on amorphous carbon electrodes from an aqueous solution of electrolytes, 43 in high-vacuum chambers by pulsed laser deposition 44,45 or by evaporation of a bulk alloy on a liquid hydrocarbon substrate. 46 Reports on structure-property relationships of these nanoparticles have produced conicting information, particularly regarding their plasmonic and magnetic responses.…”

“…46 Reports on structure-property relationships of these nanoparticles have produced conicting information, particularly regarding their plasmonic and magnetic responses. For instance, both blue- 31,45 and red-shied 34,35,39,40 plasmon resonances, compared to that of pure gold nanoparticles, were assigned to AuFe alloys with the same stoichiometry. Indeed, the characterizations of alloys were not accurate enough to exclude phase segregation or to conrm homogeneous alloying at the single nanoparticle level.…”

“…Indeed, the characterizations of alloys were not accurate enough to exclude phase segregation or to conrm homogeneous alloying at the single nanoparticle level. 31,34,35,39,40,45 This is a relevant point, since bottom-up synthetic approaches oen yield byproducts such as clustered iron atoms in the gold matrix, [36][37][38][39][40]47 iron-gold core-shell structures 11,34,35 or iron oxidegold heterostructures and agglomerates, [39][40][41]44 owing to the unfavorable thermodynamics in the formation of Au-Fe alloys. 28 Moreover, the AuFeNPs obtained by all previous methods were found to have problems related to surface accessibility, 15,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] which is important to catalytic applications [18][19][20] and for conjugation with functional molecules.…”

“…31,34,35,39,40,45 This is a relevant point, since bottom-up synthetic approaches oen yield byproducts such as clustered iron atoms in the gold matrix, [36][37][38][39][40]47 iron-gold core-shell structures 11,34,35 or iron oxidegold heterostructures and agglomerates, [39][40][41]44 owing to the unfavorable thermodynamics in the formation of Au-Fe alloys. 28 Moreover, the AuFeNPs obtained by all previous methods were found to have problems related to surface accessibility, 15,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] which is important to catalytic applications [18][19][20] and for conjugation with functional molecules. [11][12][13] Thus, new low-cost and non-toxic synthetic methods that allow the synthesis of large amounts of well-dispersed and accessible nanoparticles avoiding the thermodynamic limitations to alloy formation are needed.…”