A facile growth control of perovskite SrTiO3 thin films by tailoring surface morphologies of TiN seeding layers in the hydrothermal-galvanic couple synthesis

Growth control of cubic perovskite structure strontium titanate (SrTiO3) thin films was facilely achieved by tailoring surface morphologies of the TiN seeding layer in the hydrothermal-galvanic couple (HT-GC) synthesis. Two types of TiN thin films with pyramidal (P-TiN) and granular (G-TiN) surface morphologies were deposited on Si substrates by sputtering. The TiN-coated Si working electrodes were then directly connected to the Pt counter electrode without applying any external power source and soaked in 0.1 M Sr(CH3COOH)2 mixed with 2 M NaOH at 80 °C for 1–60 min. Significant galvanic currents were detected during the HT-GC synthesis. Directional oriented cubic SrTiO3 thin films grew over the two types of highly preferred oriented TiN seeding layers. The growth kinetics of SrTiO3 was deduced by fitting the coverage of the oxide over the two types of TiN at different reaction times to a modified Avrami equation. It was shown that galvanic currents, relative peak integrated intensities, and growth rates of SrTiO3 over the P-TiN were much higher than those on the G-TiN, while the grain sizes of SrTiO3 over the P-TiN were smaller. The faceted surfaces with fewer phase boundaries for P-TiN could yield a different rate-limiting step during the HT-GC synthesis and enhance significantly the growth of the oxide. This facile growth control could also be applied to similar perovskite oxide/conductive nitride systems.