MICROSTRUCTURAL DEVELOPMENT OF THIN-FILMS GROWN BY PULSED-LASER DEPOSITION

Pulsed laser deposition (PLD) of thin films involves conditions that d iffer substantially from those of other vapor deposition techniques an d that may be expected to influence film nucleation and growth mechani sms. In order to study the effect of these conditions on these mechani sms, a series of films was deposited using discrete numbers of laser p ulses ranging from 1 to 3000. The films were YBa2Cu3O7-delta (YBCO) an d Sr0.5Ba0.5TiO(3) (SET) and the substrates were single-crystal (100) MgO and (100) LaAlO3 (LAG), or YBCO films deposited by PLD on (100) Mg O substrates. Substrate temperatures ranged from 675 to 875 degrees C. Characterization of the surfaces by atomic force microscopy showed th at both SET and YBCO films exhibited an island growth mechanism. For t he same number of pulses, SET films were smoother than YBCO films due to the smaller unit cell height of SET. X-ray diffraction and cross-se ctional transmission electron microscopy showed that the crystal quali ty of SET films improved with increasing deposition temperature and wa s higher for films on LAO substrates than for those on MgO. The LAO su bstrates were found to be microscopically smoother than MgO substrates . The island growth mechanism observed was similar to that of other va por deposition techniques and suggests that the high vapor flux and pu lsed nature of the PLD flux did not have a substantial effect on the n ucleation and growth mechanisms.