Stabilization of ambient sensitive atomic layer deposited lanthanum aluminates by annealing and in situ capping

Abstract

We have studied the effect of air exposure on lanthanum aluminates (LaAlOx) deposited by atomic layer deposition. Fourier transform infrared spectroscopy and thermal desorption spectroscopy of as-deposited LaAlOx showed that H2O is absorbed during air exposure and that the amount of absorbed H2O increases with increasing La atomic percent. C was found to be incorporated already during deposition in the form of carbonates. H2O and CO2 are outgassed during postdeposition annealing in an inert atmosphere. After a 700 degrees C postdeposition anneal, the LaAlOx becomes resistant against H2O absorption due to film densification. Alternatively, in situ capping of the LaAlOx with a similar to 2 nm thin Al2O3 film protects the LaAlOx against H2O absorption, but it also hinders the outgassing of the C contaminants during a postdeposition anneal. (C) 2011 American Institute of Physics. [doi:10.1063/1.3557501]