Novel two-dimensional perovskites

Rare-earth titanium oxides show the systematics for a new way to tailor superlattices in bulk crystals. It is shown that series of periodic structures can be created from well-known ABO3 compounds by the process of oxygen intercalation, i.e. by an ordered incorporation of excess oxygen to form AB03+y compositions. The intercalation process slices the threedimensional ABO3 structure into subunits of different thickness, each representing a defined oxygen composition. These basic structural units are members of a homologous series, which can be combined in various ways to form new superlattices, the physical character of which varies between that of a semiconductor and a ferroelectric insulator. In contrast to the usual procedure of extrinsic doping, which creates disorder, these variations are achieved without changing the chemical character of the compounds.