Bench scale evaluation of batch mode dip-coating of sol-gel LaAlO/sub 3/ buffer material

Abstract

In a joint program between the University of Tennessee Space Institute (UTSI) and Oak Ridge National Laboratory (ORNL), thin films of lanthanum aluminate (LAO) were formed on [100] strontium titanate (STO) single crystals and on biaxially textured nickel by dip-coating from sol-gel precursors and then annealing. XRD texture measurements were used to evaluate coating parameters including substrate withdrawal speed, degree of hydrolysis, and thermal processing temperature, duration, and atmosphere. LAO films on the order of 1000 thick showed 100% biaxial epitaxy on STO single crystals but only about 50% in-plane epitaxy on nickel. An increase in substrate withdrawal velocity resulted in thicker films. On STO film texture degraded with increased film thickness, but on nickel this effect was not noted, being obscured as a result of the rather poor and variable texture of the nickel substrate used. LAO on STO texture was improved by increases, within the ranges investigated, in the degree of hydrolysis, and in the thermal processing time, temperature, and oxygen concentration. No impediments to production scale-up were found.