Emission spectral-component monitoring and fuzzy-logic control of pulsed-laser-deposition process

Pulsed-laser-deposition (PLD) is a versatile and efficient deposition technique capable of producing high quality thin-films. However, the overall process is quite complex and, as yet, not well understood. The in-situ behavior of the laser-beam-generated YBa2Cu3O7-x (YBCO) plume can be monitored using emission spectroscopy. The plume characteristics are a consequence of the interaction between a KrF excimer laser pulse (lambda = 248 nm) and a YB;CO target in ambient oxygen during the PLD of YBCO films. Plume spectral components are primarily monitored at a position midway along the normal between the target and substrate. Signal intensities are recorded at 326 +/- 5 nm (excited neutral copper atoms, Cu*, at 324.7 nm and 327.4 nm). Manual regulation of the ablation energy of the laser pulses by plume spectral component feedback produces significantly improved YBCO films. A fuzzy-logic controller using in-situ emission spectroscopy feedback, has been developed and utilized to self-direct film depositions. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.