Ferroelectric polarization imaging using apertureless near-field scanning optical microscopy

This paper reviews the technique of apertureless near-field scanning optica l microscopy (ANSOM) and its use in mapping the inhomogeneous ferroelectric polarization in BaxSr1-xTiO3 thin films. A preliminary survey compares ANS OM with fiber-based near-field microscopy, highlighting the advantages and limitations of both methods. Interferometric ANSOM is described in detail, including a practical description of how ANSOM images are acquired. A discu ssion of the various contrast mechanisms in ANSOM is followed by a prescrip tion for eliminating a certain class of topographic artifacts. For the imag ing of polarization in ferroelectric thin films, the linear electro-optic e ffect provides the central contrast mechanism. High-resolution ANSOM images show the existence of polar nanodomains in BaxSr1-xTiO3 films, providing s trong direct evidence of its relaxor character. (C) 2000 American Institute of Physics. [S0021-9606(00)70916-0].