Achieving a high energy storage density in Ag(Nb,Ta)O3 antiferroelectric films via nanograin engineering

Due to its lead-free composition and a unique double polarization hysteresis loop with a large maximum polarization (P-max) and a small remnant polarization (P-r), AgNbO3-based antiferroelectrics (AFEs) have attracted extensive research interest for electric energy storage applications. However, a low dielectric breakdown field (E-b) limits an energy density and its further development. In this work, a highly efficient method was proposed to fabricate high-energy-density Ag(Nb,Ta)O-3 capacitor films on Si substrates, using a two-step process combining radio frequency (RF)-magnetron sputtering at 450 degrees C and post-deposition rapid thermal annealing (RTA). The RTA process at 700 degrees C led to sufficient crystallization of nanograins in the film, hindering their lateral growth by employing short annealing time of 5 min. The obtained Ag(Nb,Ta)O-3 films showed an average grain size (D) of similar to 14 nm (obtained by Debye-Scherrer formula) and a slender room temperature (RT) polarization-electric field (P- E) loop (Pr approximate to 3.8 mu C center dot cm(-2) and P-max approximate to 38 mu C center dot cm(-2) under an electric field of similar to 3.3 MV center dot cm(-1)), the P-E loop corresponding to a high recoverable energy density (W-rec) of similar to 46.4 J center dot cm(-3) and an energy efficiency (eta) of similar to 80.3%. Additionally, by analyzing temperature-dependent dielectric property of the film, a significant downshift of the diffused phase transition temperature (TM2-M3) was revealed, which indicated the existence of a stable relaxor-like