Thickness dependence of dielectric properties in bismuthlayer-structured dielectrics

c -axis-oriented epitaxial Sr Bi 4 Ti 4 O 15 and Ca Bi 4 Ti 4 O 15 films having natural superlattice structure were grown on ( 001 ) c Sr Ru O 3 || ( 001 ) Sr Ti O 3 substrates by metal organic chemical vapor deposition. Sr Bi 4 Ti 4 O 15 films suffer no degradation with a dielectric constant of 200 down to a film thickness of 15 nm , which corresponds to four unit cells. Temperature coefficients of capacitance were low enough despite their high dielectric constant. They exhibited stable capacitance and superior insulating properties against applied electric field, irrespective of film thickness. These results open the door to designable size-effect-free materials with high dielectric constant having bias- and temperature-independent characteristics together with superior electrical insulation for high-density capacitor applications.