Etching study of ferroelectric microdomains in LiNbO3 and MgO:LiNbO3

Ferroelectric microdomains in Czochralski-grown congruent LiNbO3 and 5 mol% MgO:LiNbO3 were studied by chemical etching with hydrofluoric acid followed by characterization of the +Z and -Z surfaces with optical microscopy and scanning electron microscopy. Both materials contained reverse-polarized microdomains with domain walls formed by non-polar{<11(2)over bar 0}) surfaces and most likely bounded by (0001) surfaces. The shapes of the microdomains in the (0001) plane for congruent LiNbO3 were always regular hexagons, while those in MgO:LiNbO3 were irregular hexagons with 120 degrees angles. For both materials, dimensions of the microdomains in the (0001) plane averaged about 5 mu m and were as large as 12 mu m in congruent LiNbO3 and 25 mu m in MgO:LiNbO3. The areal density of reverse-polarized microdomains across one 3 inch (7.6 cm) diameter wafer averaged about (5-10)x10(3) cm(-2) within the inner 5 cm diameter of the wafer, corresponding to a volume fraction of reverse-polarized material of about 0.1-0.2%.