Microwave induced breakdown spectroscopy: Insights into plasma dynamics and spectrum analysis.

Microwave-Induced Breakdown Spectroscopy (MIBS) uses a localized microwave antenna to generate plasma directly on the solid sample surface, making it an efficient and cost-effective method for identifying material elemental composition. Unlike typical microwave optical emission spectroscopy methods that require high gas flow rates or complicated setups, the antenna-based MIBS method eliminates the need for extensive sample preparation and environmental constraints. This study investigates the dynamic characteristics of microwave-induced plasma (MIP) through the evolution of emission intensity using both spectroscopic and image analysis techniques. The temporal studies of spectral signal were conducted on different material types, i.e., aluminum, iron, and ceramics, followed by a detailed investigation of the plasma evolution and the impacts of microwave power, pulse durations, and repetition rate, performed on an aluminum sample. The results demonstrate that microwaves emitted from an antenna generate plasma on the sample surface with high emission intensity. Temporal spectral evolution studies reveal that plasma emission and lifetime are sustained by the microwave pulse, with the highest signal intensities for atomic and ionic emission lines observed at the end of the microwave pulse, regardless of material type. For aluminum and iron, signal intensities disappear beyond 1000 μs, indicating rapid plasma decay. In contrast, ceramics exhibit a longer-lived plasma, with measurable emission persisting up to 1200 μs. For the aluminum sample, increasing MW power from 1000 W to 3000 W enhances signal intensity from 0.9 × 104 a.u to 2.4 × 104 a.u due to increase in plasma temperature from ∼7100 K to 7600 K and electron density from 2.2 × 1017 to 2.7 × 1017 while reducing measurement uncertainty by increasing the likelihood of plasma formation. Further investigation of pulse duration and repetition rate effects reveals that a longer pulse improves emission intensity by supplying more energy, whereas low repetition rates stabilize the signal by enabling plasma cooling. These findings suggest that antenna-based MIBS provides a sophisticated and cost-effective alternative to existing spectroscopic techniques, offering the added benefit of direct microwave plasma generation compared to other microwave optical emission and laser spectroscopic methods.