TOF-SIMS Analysis Using Bi₃ ⁺ as Primary Ions on Au Nanoparticles Supported by SiO₂/Si: Providing Insight into...

Area of Science:

• Surface Science
• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Understanding nanoparticle-support interactions is critical for heterogeneous catalysis.
• Gold nanoparticles (Au NPs) on silicon (Si) substrates are model systems for studying metal-support interfaces.
• The chemical state of nanoparticles on surfaces can change upon thermal treatment.

Purpose of the Study:

• To investigate the effect of annealing on the interaction between Au nanoparticles and a Si wafer surface.
• To explore the utility of secondary ion mass spectroscopy (SIMS) with cluster ions for analyzing surface chemical states.
• To understand the formation of new chemical species at the nanoparticle-support interface.

Main Methods:

• Preparation of Au nanoparticles (20 nm diameter, ~20% surface coverage) on Si wafers.
• Annealing of samples at 100 °C and 300 °C.
• Analysis using SIMS with Bi3+ primary ions and Ar1000+ cluster ion sputtering.

Main Results:

• Distinct differences in SIMS spectra were observed between non-annealed and annealed samples.
• Non-annealed samples showed bare Au cluster cations and Si+.
• Annealed samples exhibited AuSi+ clusters, indicating the formation of gold silicide at the nanoparticle periphery.

Conclusions:

• Annealing induces the formation of gold silicide at the interface between Au nanoparticles and the Si wafer.
• SIMS using cluster ions (Bi3+) provides valuable information on local chemical environments beyond elemental composition.
• Caution is advised when using prolonged Ar1000+ sputtering in SIMS, as it can alter surface structures.