ABSTRACT
It is useful to begin with what is known in general about radiation damage in ferroelectrics, and then to consider what special phenomena occur for thin-film memories. In 1957 Wittels and Sherill showed1 that large total doses of X-rays converted tetragonal, ferroelectric barium titanate to the cubic, paraelectrico phase. Lefkowitz and Mitsui later found, surprisingly, that irradiation lowered the coercive field of this material; whereas in TGS it increases, according to the study by Chynoweth, and a large bias field develops. For prolonged exposure the bias field Eg exceeds the coercive field Ec, so that switching occurs for only one polarity of access voltages.
