Space-charge-limited current in thin PLZT samples

Abstract

Abstract Currents in thin (9 and 24 μm) samples of PLZT 8/65/35 decrease with time by up to five orders of magnitude, then they may spontaneously change direction and flow for hours opposite to the applied field. This is explained by injection of free charge (electrons or holes). The injected charge causes a space-charge-limited current which is much larger than the conductivity current. With time more and more injected carriers are trapped on various defects of the ferroelectric sample. The trapped charge builds up an electric field opposite to the applied field, reducing the current and changing the internal field of the sample. The space charge collected on domain walls may then cause domains to flip over. As a result, the internal field exceeds the applied field and the current reverses direction. Various other aspects of space-charge-limited currents and their measurements in polar materials are discussed.