Oxide Electrodes for Pb(Zr0.52Ti0.48)O3 Capacitors

Ferroelectric thin films have been widely studied to understand the fundamental physics and for applications because of their ferroelectric non-volatile memory and fast switching characteristics. Typically, a layer of ferroelectric material is sandwiched between a pair of electrodes to realize the functionalities in capacitors. Conductive oxide materials with the perovskite structure are a suitable template to epitaxially grow the subsequent ferroelectric PZT layer for high-performance devices. Currently, SrRuO3 (SRO) and LaNiO3 (LNO) are widely
used as electrodes in PZT capacitors in the laboratory. However, attention needs to be given to the resistivity of these oxide electrodes, and the lattice mismatch between the electrode layers and PZT. Growth mechanisms of La0.07Ba0.93SnO3 (LBSO) and SrVO3 (SVO) are reported. Because lattice constant of LBSO is perfectly matched with PZT and SVO has high conductivity. The conclusion of the growth study is that kinetic effects and oxidation species both make a contribution to determine the growth mode in PLD. The performance of PZT capacitors with an electrode of LBSO or SRO was studied. This work clearly shows the work function and the carrier density of oxide electrodes in ferroelectric devices play an important role in the polarization switching and fatigue properties. A conductive oxide material with a high work function and high carrier density is required for PZT ferroelectric devices. The properties of SVO in a heterostructure was studied in the last chapter. The metal-insulator transition (MIT) of SrTiO3 (STO) capped SVO ultrathin films and SVO/STO superlattices were observed. The conductivity enhancement in SVO/STO superlattices compared to the single SVO/STO bilayer is explained by interlayers coupling effects.