Abstract
This study presents observations of the microstructural development of epitaxial KTaO3 films grown hydrothermally at 170oC in 7M KOH solutions. KTaO3 is used in tunable microwave devices and, as a buffer layer, improves the alignment of epitaxial KNbO3 films grown hydrothermally at 200oC on SrTiO3 substrates. KNbO3 is a very promising material for applications such as frequency doubling, wave guiding and holographic storage. The KTaO3 film formed by the island growth mode and the island size decreased with increasing precursor concentration. As a result, films grown with higher precursor concentrations coalesced earlier at smaller film thicknesses. Film cracking also occurred at smaller thickness when higher precursor concentrations were used. Therefore, it is believed that film cracking occurred as a result of grain coalescence or the ′zip-up′ effect. The cracking occurred at the edges first where the critical thickness was reached earlier.
