Improved methods for design of PLD and combinatorial PLD films

Pulsed laser deposition (PLD) is a powerful technique for prototyping thin film materials, both single component (single composition) films and films with a varying composition (e.g., lateral continuous compositional spread, CCS). In this work, we improve one of the simulation methods used to design the deposition of PLD films: We extend the mathematical model for the material spread on the substrate, T1(x,y), for each laser pulse hitting the target, and we use a more accurate method to determine T1(x,y) experimentally. The deposition of the material on the substrate is simulated by repetitively adding T1(x,y), from one or more targets, at the selected location on the substrate. Using the new model, a high agreement between the simulated and grown films’ thickness and composition across the substrate was obtained. The basis for the high agreement is the use of variable angle spectroscopic ellipsometry to carefully determine T1(x,y) by measuring at 794 locations on the 50.8 mm (2 in.) diameter substrates. Factors, such as variation in optical properties and porosity across the plume/calibration films, were considered in the determination of the thicknesses. As test cases, we simulated and deposited (single component) TiO2 thin films and (CCS) TiO2 films doped with Cr and N, deposited on 50.8 mm diameter Si wafers. The modeling and simulations are implemented in an open-source Python library, pyPLD.