DOMAIN FORMATION IN THIN FERROELECTRIC-FILMS - THE ROLE OF DEPOLARIZATION ENERGY

Formulae for equlibrium stripe domain width W-eq in a nonductive ferro electric plate of thickness d are deduced, taking into account electro static interaction of surfaces. It is shown that the classical formula giving W-eq infinity d(1/2) is not applicable when the sample thickne ss decreases below the value d(crit) which is a function of dielectric properties and domain wall energy density. For many ferroelectrics th e value of d(crit) lies in a range which can be easily reached far bel ow the transition point by contemporary thin film techniques; it furth er increases as the transition point is approached. In the region d < d(crit) the width W-eq increases with decreasing d. For samples with t hickness d << d(crit) the domain structure becomes insensitive to elec trical boundary conditions and will be primarily determined by other f actors.