Citation

Sohn Y, Pradhan D, Radi A, Leung KT. Langmuir 2009; 25(16): 9557-9563.

Copyright

(Copyright © 2009, American Chemical Society)

DOI

10.1021/la900828v

PMID

unavailable

Abstract

Gold nanoparticles (Au NPs) were prepared on a native-oxide-covered Si(100) substrate by sputter-deposition followed by thermal annealing. The size of Au NPs could be controlled in the range of 8-48 nm by varying the sputterdeposition time and post-annealing temperature. The interparticle separation was found to be directly related to the size of Au NPs, with smaller separations for particles of smaller size. The surface morphology, crystal structure, and interfacial composition of the chemical states of these supported Au NPs were studied as a function of their average size by using scanning electron microscopy, glancing-incidence X-ray diffraction, and depth-profiling X-ray photoelectron spectroscopy (XPS), respectively. The new Au 4f7/2 peak found at 1.1 -1.2 eV higher in binding energy than that for the metallic Au feature (at 84.0 eV) can be attributed to the formation of Au silicide at the interface between Au NPs and the Si substrate. Depth-profiling XPS experiments revealed no discernible change in the binding energies of the Au silicide and metallic Au 4f features with increasing Ar+ sputtering time, indicating that the Au-to-silicide interface is abrupt. Furthermore, the shift in the Au 5d5/2 valence band to a higher binding energy and the reduction of the Au 5d spin-orbit splitting with increasing Ar+ sputtering time also support the formation of Au suicide. No clear evidence for the quantum size effect was observed for the supported NPs. The finite density of state at the Fermi level and the fixed Au 4f7/2 peak position clearly indicate the metallic nature of the Au suicide at the Au-Si interface. © 2009 American Chemical Society.

Language: en

Keywords

Silicon; Scanning electron microscopy; Gold alloys; Gold; X ray photoelectron spectroscopy; Surface structure; Silicides; Substrates; Binding energy; Sputtering; XPS; Depth profiling; Crystal structure; Electronic structure; Nanoparticles; Si substrates; Thermal-annealing; Potential energy; Metallic compounds; Average size; Binding sites; Chemical state; Finite density; Glancing-incidence X-ray diffraction; Gold deposits; Gold nanoparticle; Gold Nanoparticles; Inter-particle separation; Interfacial composition; Interfacial electronic structure; Nuclear energy; Peak position; Post-annealing temperature; Quantum size effects; Si (100) substrate; Si(1 0 0); Size separation; Spin-orbit splittings; Sputter-deposition; Sputtering time