Ion polishing of copper: some observations

Area of Science:

• Materials Science
• Surface Science
• Optical Engineering

Background:

• Copper's absorptivity is critical for optical components.
• Surface imperfections increase absorptivity.
• Advanced polishing techniques are needed to minimize surface damage and enhance optical properties.

Purpose of the Study:

• To investigate the effect of ion polishing on copper absorptivity at 10.6 micrometers.
• To characterize the ion polishing apparatus and process.
• To determine the reduction in absorptivity achievable through ion polishing combined with annealing.

Main Methods:

• Describing an ion polishing apparatus utilizing a low-energy Xenon (Xe) ion beam at a glancing angle.
• Implementing sample rotation and beam scanning for uniform material removal.
• Measuring absorptivity using calorimetry on mechanically and electropolished copper samples before and after ion polishing and annealing.

Main Results:

• Absorptivity of mechanically polished copper reduced from 0.92% to 0.76% after ion polishing and annealing.
• Absorptivity of electropolished copper reduced from 0.97% to 0.89% after ion polishing and annealing.
• Scanning Electron Microscopy (SEM) indicated smoother surface features with ion polishing.

Conclusions:

• Ion polishing is an effective method for reducing copper absorptivity at 10.6 micrometers.
• Combining ion polishing with vacuum annealing further enhances absorptivity reduction.
• The developed ion polishing technique minimizes ion penetration and damage while maximizing material removal rate.