Domain reversal control method for ferroelectric materials

A domain reversal alignment method for forming photolithographic mask alignment keys on surfaces of a unidirectionally polarized ferroelectric material comprising:

• providing a substrate which is a unidirectionally polarized ferroelectric material having opposing first and second planar surfaces which are substantially parallel and wherein said polarization is directed substantially towards said first surface from said second surface;
• forming a metallic or metal oxide conducting layer on the first surface of said substrate, said layer having an alignment key shape;
• producing an electric field within an interior region of the substrate between the first and second substrate surfaces and beneath said conducting layer, said electric field reversing the unidirectional polarization within said region;
• and then
• removing said conducting layers;
• and
• etching substrate first and second surfaces to produce, thereby, surface indentations having said alignment key shape on both the first and second substrate surfaces, the indentation on the first surface being vertically aligned with a corresponding indentation on the second surface and said surface indentations forming alignment keys for the subsequent alignment of photolithographic masks over said surfaces.

A method for forming uniform domains of reversed polarization within a unidirectionally polarized ferroelectric material comprising:

• providing a substrate that is a unidirectionally polarized ferroelectric material having opposing first and second planar surfaces which are substantially parallel and wherein said polarization is directed substantially vertically towards said first surface and away from said second surface;
• forming alignment keys on said planar surfaces;
• using said alignment keys, forming, by a first process, a plurality of periodically spaced regions on said first surface and forming, by a second process, a plurality of periodically spaced regions on said second surface, all of said regions on said first surface being exposed or electrically contacted by a conducting layer and each of said regions being vertically aligned with a corresponding region on said second surface and all of said second surface regions being exposed or electrically contacted by a conducting layer;
• coating all exposed surface regions with a conducting liquid;
• electrically contacting the conducting liquid or conducting layer on said corresponding surface regions formed on said first and second surfaces;
• producing an electric field within said substrate between said corresponding electrically contacted regions and thereby reversing said unidirectional polarization within the substrate interior between said regions.