Application of Ion Energy Spectroscopy for Monitoring Plasma Dynamics in Pulsed Laser Deposition of Complex Metal Oxide Thin Films*

Understanding and controlling plasma energetics during Pulsed Laser Deposition (PLD) is fundamental to achieving high-quality complex metal oxide thin films. This work involved the in-situ use of an Ion Energy Spectrometer (IES) for measuring the kinetic energy distribution of ablated ions from a SrTiO₃(STO) target. IES is an electrostatic retarding field type spectrometer where ions are separated from electrons and are discriminated by their kinetic energy by applying variable biasing voltages. This capacity allows for the real-time monitoring of the energy and flux of ions at the substrate as influenced by changes in laser fluence, process pressure, and target–substrate (T–S) geometry. Preliminary IES measurements show that higher laser fluence and shorter T–S distances yield a greater proportion of high-energy ions (>60 eV) in vacuum, indicating enhanced forward momentum and reduced plume scattering. Guided by these results, STO films were deposited on (100) oriented LaAlO₃ (LAO) at 760 °C and 350 mJ using 3k pulses in vacuum. Electrical tests revealed a significant drop in resistance from MΩ to kΩ range as T–S distance decreased, while resistivity measurements confirmed semiconducting behavior with improved conductivity for the film grown with a T-S distance of 5 cm This study establishes the IES as a powerful real-time diagnostic for quantifying plasma dynamics and correlating them with film properties. We are currently extending this work to the growth of other metal oxide materials. Continuing work will extend this approach to analyze structural, morphological, and compositional effects, building a predictive framework for optimizing energy-tuned PLD growth across a range of oxide material systems.