Epitaxial growth and properties of lead-free ferroelectric Na0.5Bi0.5TiO3 thin films grown by pulsed laser deposition on various single crystal substrates

The epitaxial growth of lead-free ferroelectric Na
_0.5
Bi
_0.5
TiO
₃
(NBT) thin films on various single crystal substrates was successfully achieved, using the pulsed laser deposition technique (PLD). The present work is divided in two parts, focused on: (i) the growth of NBT layers on c- and r-sapphire (Al
₂
O
₃
) substrates, with and without introducing a CeO
₂
buffer layer, and (ii) the growth of NBT layers on bare (001)SrTiO
₃
substrates, with and without introducing a LaNiO
₃
layer, that could be used as a bottom electrode. In the first part, it was shown that the introduction of a CeO
₂
buffer layer completely modifies the out-of-plane growth orientation of the NBT films, as well as their microstructure. Indeed, (001)NBT films epitaxially grow only on r-Al
₂
O
₃
substrates buffered with epitaxial (001)CeO
₂
layers, while, growing simply NBT on top of bare c or r-Al
₂
O
₃
substrates, or on top of CeO
₂
/c-Al
₂
O
₃
heterostructures leads to polycrystalline or textured films. In the second part, we demonstrate that (001)-oriented NBT layers deposited on either bare (001)SrTiO
₃
or (001)SrTiO
₃
substrates (STO) covered with (001)LaNiO
₃
(LNO) are systematically epitaxially grown. Furthermore, the microstructure of the samples is strongly affected by the introduction of the LaNiO
₃
layer.