New Insight into the Gas Phase Reaction Dynamics in Pulsed Laser Deposition of Multi-Elemental Oxides

Area of Science:

• Plasma Physics
• Laser Ablation
• Gas-Phase Kinetics

Background:

• Laser-induced plasma dynamics depend on target material and background gas interactions.
• Ablation of metal (M) and metal-oxide (MO) species in Ar and O2 backgrounds is investigated.
• Previous studies show similarities in M+ ion expansion in Ar and O2 when MO+ dissociation energy is low.

Purpose of the Study:

• To investigate how background gas composition (Ar vs. O2) affects laser-induced plasma plume expansion dynamics.
• To determine the influence of metal-oxygen (MO+) species formation on plume expansion.
• To identify the kinetic energy range favorable for MO species formation via chemical reactions in expanding plasmas.

Main Methods:

• Laser ablation of metal targets in controlled Ar and O2 gas backgrounds.
• Analysis of gas-phase reaction dynamics and kinetics within the plasma.
• Measurement of ion species and their kinetic energies during plume expansion.

Main Results:

• Plume expansion in O2 differs from Ar, particularly for metal ions where MO+ dissociation energy exceeds O2's.
• The formation of MO+ species is identified as a key factor differentiating expansion dynamics in O2 compared to Ar.
• At high oxygen pressures, MO species are predominantly formed through chemical reactions within the expanding plasma at kinetic energies up to 5 eV.

Conclusions:

• Background oxygen significantly alters laser-induced plasma plume expansion compared to inert gases like argon.
• The dissociation energy of MO+ relative to O2 is critical in determining expansion behavior.
• Optimizing kinetic energy is crucial for controlling chemical reactions and MO species formation in oxygen-rich plasmas.