Velocity distribution function of sputtered Cu atoms obtained by time resolved optical absorption spectroscopy

Area of Science:

• Plasma Physics
• Materials Science
• Spectroscopy

Background:

• Magnetron plasma discharges are crucial for thin film deposition.
• Understanding sputtered atom behavior is key to controlling film properties.
• Existing methods for measuring sputtered atom velocities have limitations.

Purpose of the Study:

• To introduce a new time-resolved optical absorption spectroscopy method.
• To determine the velocity distribution function of sputtered copper (Cu) atoms.
• To investigate the spatial evolution of these velocity distributions.

Main Methods:

• Utilized time-resolved optical absorption spectroscopy.
• Applied a short 1.5-microsecond pulse.
• Recorded time variations in Cu atom density at 1, 2, and 3 cm from the target.
• Converted density evolution to velocity distributions.

Main Results:

• The method detects sputtered atoms with radial velocities below 0.5 km/s.
• Velocity distributions become more dispersed with increasing distance from the target.
• Average Cu atom velocities range from 2.5-3 km/s near the target.
• At 3 cm and 30 mTorr, average velocities decrease from 2.5 to 1.2 km/s.

Conclusions:

• The proposed spectroscopy method effectively characterizes sputtered atom velocity distributions.
• Spatially resolved velocity data provide insights into plasma-surface interactions.
• The findings contribute to optimizing magnetron sputtering processes for material deposition.