Surface-controlled growth of LaAlO3 thin films by atomic layer epitaxy

LaAlO3 thin films were deposited by atomic layer epitaxy (ALE) from beta -d iketonate-type precursors La(thd)(3) and Al(acac)(3). Ozone was used as an oxygen source. Films were grown on soda lime glass, Si(100), MgO-buffered S i(100), sapphire and SrTiO3(100) Substrates. The influence of the La:Al pre cursor pulsing ratio on the film growth and quality in the temperature rang e of 325-400 degreesC was studied in detail. Stoichiometry and impurity lev els were measured using RBS, TOF-ERDA and XPS while the chemical type of ca rbon impurity was identified by FTIR. XRD and AFM were used to determine cr ystallinity and surface morphology. The films were transparent and uniform and their thickness could be accurately controlled by the number of deposit ion cycles. The as-deposited films were amorphous but became crystalline up on annealing at 900 degreesC. The annealed films grown on Si(100) and MgO(1 11)-buffered Si(100) substrates had a preferred (110) orientation whereas t hose grown on MgO(100)-buffered Si(100) substrates showed a preferred (100) orientation. Epitaxial and smooth LaAlO3 thin films were obtained on SrTiO 3(100) after annealing at 900 degreesC, verified by measurement of the X-ra y rocking curve of the (200) reflection and the AFM surface roughness. Stoi chiometric LaAlO3 films contained <1.9 atom% carbon and about 0.3 atom% hyd rogen as impurities.