Application of Ion Energy Spectroscopy to Optimize the Pulsed Laser Deposition Parameters for SrTiO3−y Films

Abstract Reproducible modulation of subtle property variations in metal oxide thin films by pulsed laser deposition (PLD) involves optimizing a multiparameter process with several coupled deposition parameters. This task can be simplified by utilizing the fact that three of the key deposition parameters—the laser fluence, the target-to-substrate distance, and the ambient gas pressure—influence the film properties through the ion energy distribution in the plasma plume. Thus, mapping the ion energy distribution during film growth in real time serves to generate a signature graph representing a combination of these three deposition parameters. Ion energy spectroscopy (IES) is a recently developed tool that measures the plasma ion energy distribution in real time. Here, we report our research on using IES characterization for the growth of strontium titanate thin films by PLD. We observe that the measured ion energies have a direct correlation with laser fluence and an inverse correlation with the oxygen pressure. Films deposited under lower oxygen pressure show lattice expansion and increased electrical conductivity characteristic of oxygen deficiency that can originate from the oxygen loss due to re-sputtering bombardment by high-energy ions, in addition to the reduction in oxygen incorporation rates. Increasing the laser fluence also has similar effects on the lattice constants, indicating oxygen loss due to re-sputtering. However, the resistivity increases with laser fluence, which may be attributed to the defects induced by ion bombardment. Our results demonstrate the potential of IES analysis for the optimization of metal oxide thin film growth by PLD.