Subsurface nanodomains with in-plane polarization in uniaxial ferroelectrics via scanning force microscopy

摘要

Ferroelectric nanodomains can be created by the application of a bias voltage to the sharp conducting tip of a scanning force microscope (SFM) contacting the sample surface. Since an inhomogeneous electric field created by an SFM tip has maximum intensity along the surface normal, in multiaxial ferroelectrics the polarization inside these domains also tends to orient perpendicularly to the surface. Here we show theoretically that unusual domains can be created in uniaxial ferroelectrics when the SFM tip is applied to the crystal surface parallel to the polar axis. These 180° nanodomains have polarization directed along the surface and should appear in LiNbO_3 and LiTaO_3 crystals at moderate tip voltages well below 100 V. Calculations of equilibrium domain dimensions demonstrate that subsurface domains have the shape of a needle oriented along the polar axis.