Photochemical Investigation of a Polarizable Semiconductor, Lead-Zirconate-Titanate

In this work, we have investigated the photochemical reaction with a variety of metal salts on a polarizable semiconductor, lead zirconate titanate (PZT 30/70 [111]). The exact position of the band edges can influence properties such as the width of the space-charge region and barriers for charge injection, which play an important role in devices built with such materials such as FeRAM and MLC. Observations show that there can be metal deposition on positive domains or photodecomposition on negative domains. The exact reaction was found to be dependent on the reduction potential of the cation and whether a nitrate or chloride salt was used. We show that for certain cations such as Fe 2+, with a reduction potential near the edge of the conduction band of the PZT, either reduction or photodecomposition can happen. This effect can be explained because of the presence of an uncertainty in the location of the band edges at the surface of the PZT. The exact position of these edges is determined by the Femi level’s pinning location, which is dependent on the surface states specific to each sample. Therefore, the location of the band edges is sensitive to the crystallization process during manufacture within a range of energies. Issues such as the location of the conduction band with respect to the vacuum and size of the band gap are of interest when incorporating ferroelectric materials into devices and impact on fundamental properties such as fatigue.