Strain relaxation and vacancy creation in thin platinum films

Area of Science:

• Materials Science
• Solid State Physics
• Surface Science

Background:

• Thin metallic films often exhibit residual stress, impacting their performance and stability.
• Understanding stress relaxation mechanisms is crucial for developing reliable thin-film devices.
• Vacancies are hypothesized to be critical in stress relaxation, especially at lower temperatures.

Purpose of the Study:

• To investigate the role of vacancies in the relaxation of residual stress in thin platinum (Pt) films.
• To experimentally determine the relationship between vacancy concentration, residual strain, and annealing time.
• To provide experimental evidence for the dominant role of vacancies in stress relaxation near room temperature.

Main Methods:

• Utilized combined in situ synchrotron X-ray diffractometry and reflectometry.
• Measured relative changes in lattice parameter (a) and film thickness (L).
• Analyzed data to derive vacancy concentration and residual strain as a function of annealing time at 130 °C.

Main Results:

• Observed a direct correlation between strain relaxation and the creation of vacancies.
• Identified vacancy creation predominantly at the free film surface.
• Quantified the modification of vacancy concentration and residual strain during annealing.

Conclusions:

• Experimentally confirmed that vacancies are created during the relaxation of compressive stress in Pt films.
• Demonstrated the significant role of vacancies in facilitating stress relaxation in thin metal films at temperatures near room temperature.
• Validated the long-postulated dominant contribution of vacancies to stress relaxation mechanisms in thin films.