Effect of electron beam writing parameters for ferroelectric domain structuring LiNbO3:Nd3+

We have successfully applied the versatile technique of direct electron beam writing to produce column shaped 180° micro-domains on a solid state laser crystal: Nd3+ doped LiNbO3. The effect of the different parameters used during the electron lithography process has been analyzed on the morphology and on the optical properties of the inverted domains. Namely, we have studied the effect of the value of the accelerating voltage of the electrons and the effect of the electronic charge deposited onto the sample. By means of optical micrography and computer simulation we show that the accelerating voltage has a major effect on the diameter of inverted domains. On the other hand, the value of the electronic charge not only affects the domain size but it has also an additional and interesting effect on the optical spectroscopy of Nd3+ ions. Using low temperature site selective optical spectroscopy we demonstrate the possibility of acting selectively on the crystal field of the optically active Nd3+ centers in LiNbO3 by means of the different electronic doses used to reverse the polarization of the matrix. The work constitutes an approach towards the control of the properties of reversal ferroelectric domains structures prepared by direct electron beam lithography and towards understanding the role of optically active defects on the switching behaviour in ferroelectric crystals.