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

Pulsed-laser-deposition (PLD) is a versatile and efficient deposition techn ique capable of producing high quality thin-films. However, the overall pro cess is quite complex and, as yet, not well understood. The in-situ behavio r of the laser-beam-generated YBa2Cu3O7-x (YBCO) plume can be monitored usi ng emission spectroscopy. The plume characteristics are a consequence of th e 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 co mponents are primarily monitored at a position midway along the normal betw een 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 re gulation of the ablation energy of the laser pulses by plume spectral compo nent feedback produces significantly improved YBCO films. A fuzzy-logic con troller using in-situ emission spectroscopy feedback, has been developed an d utilized to self-direct film depositions. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.