A Thin Film Source in a Solid-State Diffusion Experiment: CoO on SrTiO3.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Surface Science

Background:

• Quantitative analysis of diffusion profiles requires sharp interfaces.
• Fabricating such interfaces for diffusion studies is challenging.

Purpose of the Study:

• To demonstrate a thin film deposition method for creating sharp interfaces for diffusion experiments.
• To investigate cobalt (II) oxide (CoO) film growth on strontium titanate (STO) for use as a diffusion source.

Main Methods:

• Ion beam sputtering for CoO thin film deposition on STO at room temperature.
• Diffusion annealing to induce Co diffusion.
• Characterization using energy dispersive X-ray spectroscopy (EDS) in a transmission electron microscope (TEM), atom probe tomography (APT), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS).

Main Results:

• Nearly single-crystalline, epitaxial CoO films with flat, sharp interfaces on STO were achieved.
• Conditions for maintaining stable CoO layers as a constant Co diffusion source were identified.
• Partial formation of Co3O4 phase observed after diffusion annealing.
• Co-diffusion profiles were successfully measured using multiple techniques.

Conclusions:

• The demonstrated thin film method provides a reliable way to create sharp interfaces for diffusion studies.
• The CoO/STO system serves as a model for studying diffusion in oxides.
• Discrepancies in diffusion constants across different measurement scales were observed and discussed.