Long Term Stability in Thin Film Ferroelectric Memories
Abstract
The mechanism and control of the fatigue of remanent polarization in thin film ferroelectric memories is being investigated. The predicted detrimental effect of acceptor-dopants and beneficial effect of donor-dopants has been confirmed in thinned samples of BaTi03. A similar but reduced effect has been observed in thin films of PZT, and the possible effect of PbO-loss on reducing the beneficial effect of donor dopants is being investigated. It has become apparent that under high temperature equilibration conditions for perovskite titanates, the concentration of trapped holes exceeds that of free holes, contrary to earlier expectations. This means that the amount of nonstoichiometry and of trapped charge is considerably higher than previously thought. This is being explored with bulk samples of PZT. Reported problems with retention of polarization in PZT films integrated into circuits, i.e. the nonvolatile feature of the memories, has led to a new program to determine the conditions to which PZT films can be exposed without loss of essential properties. Direct observation of the motion of ferroelectric domains by transmission electron microscopy' has been achieved, and a new field stage is being designed. Thin films of Pb(Mnl/3Nb2/3)03-PbTi03 (90% PMN) have been prepared with greater than 99% perovskite phase. Thin-films, Ferroelectrics, Defects, Fatigue, PZT.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 29, 1992
- Accession Number
- ADA256290
Entities
People
- D. M. Smyth
- M. P. Harmer
Organizations
- Lehigh University