Giant energy storage density in lead-free dielectric thin films deposited on Si wafers with an artificial dead-layer

High-performance lead-free thin-film capacitors deposited on the silicon (Si) wafers with large energy storage density (W) and high reliability are strongly attractive in the modern electrical and electronic devices. Here, an ultrahigh W was achieved in the Ba0.3Sr0.7Zr0.18Ti0.82O3 (BSZT) relaxor ferroelectric thin films deposited on the Si wafers with the help of an ultrathin Ca0.2Zr0.8O1.8 (CSZ) artificial "dead-layer" simultaneously possessing high resistivity, wide band gap and high permittivity among linear dielectrics. As the CSZ was implanted, the W of the Ba0.3Sr0.7Zr0.18Ti0.82O3 (BSZT) thin films was greatly increased from 64.9 J/cm(3) to 89.4 J/cm(3), which is comparable to the best W of thin film deposited on expensive single crystal substrates, and is the largest one reported so far than those of lead-free thin films deposited on the Si wafers, and even for lead thin films. Due to the formation of ultrahigh electrons injection barrier (3.92 eV) between the interface of the CSZ dead layer and the Au top electrode, the Schottky emission of the BSZT thin films under high electric field and at high temperatures was effective suppressed, which is responsible for the greatly improved dielectric breakdown strength and thermal stability. Moreover, the fatigue endurance was also enhanced. It is concluded that the implantation of the CSZ artificial dead-layer could be used as a universal-simple-effective strategy to improve the electrical performances of ferroelectric materials working in the harsh environment of high electric field.