Increasing recoverable energy storage in electroceramic capacitors using "dead-layer" engineering

The manner in which ultrathin films of alumina, deposited at the dielectric-electrode interface, affect the recoverable energy density associated with (BiFeO3)(0.6)-(SrTiO3)(0.4) (BFST) thin film capacitors has been characterised. Approximately 6 nm of alumina on 400 nm of BFST increases the maximum recoverable energy of the system by around 30% from similar to 13 Jcc(-1) to similar to 17 Jcc(-1). Essentially, the alumina acts in the same way as a naturally present parasitic "dead-layer," distorting the polarisation-field response such that the ultimate polarisation associated with the BFST is pushed to higher values of electric field. The work acts as a proof-of-principle to illustrate how the design of artificial interfacial dielectric "dead-layers" can increase energy densities in simple dielectric capacitors, allowing them to compete more generally with other energy storage technologies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772016]