STEM nanodiffraction technique for structural analysis of CoPt nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Correlating nanoparticle structure with size requires linking imaging and diffraction data.
• Conventional nanobeam diffraction is time-consuming for randomly oriented nanoparticles.

Purpose of the Study:

• To develop an improved method for analyzing single nanoparticle structures and their size-dependent properties.
• To investigate size effects on the order-disorder transition temperature in cobalt-platinum nanoparticles.

Main Methods:

• Utilized a finely tuned, parallel STEM nanoprobe (1 nm, <1 mrad convergence angle) in TEM.
• Controlled STEM nanoprobe positioning to acquire diffraction patterns from individual nanoparticles selected in STEM images.
• Applied Bright and Dark Field STEM (BF/DF STEM) modes for enhanced analysis.

Main Results:

• Successfully obtained diffraction patterns from numerous single nanoparticles.
• Demonstrated a correlation between nanoparticle size and structural properties.
• Observed size effects on the order-disorder transition temperature in cobalt-platinum nanoparticles below 3 nm.

Conclusions:

• The developed BF/DF STEM technique offers an efficient alternative to nanobeam diffraction for single nanoparticle structural analysis.
• Nanoparticle size significantly influences the order-disorder transition temperature, particularly for sizes below 3 nm.
• This method facilitates the study of size-dependent phenomena in nanomaterials.