Domain orientation in ultrathin (Ba,Sr)TiO3 films measured by optical second harmonic generation

Abstract

The analysis of polarization diagrams for specular and scattered second harmonic generation ͑SHG͒ was used for the structural characterization of submicron domain structures of thin (Ba,Sr͒TiO 3 ͑BST͒ films. It is shown that the lack of separation of these two contributions may lead to completely wrong conclusions about the domain orientation in these films. SHG studies of the thickness dependence of domain fractions ͑including 180°domains͒ reveal the presence of ferroelectric domains in ultrathin BST films ͑6 nm͒, although no domain structure was observed by atomic force microscopy. Thus the presence of ferroelectric ordering was demonstrated in perovskite films with a thickness down to 6 nm.

Polar nature of stress-induced twin walls in ferroelastic CaTiO3

“…The SHGM is a powerful technique for observing some ferroic materials due to its high sensitivity to breaks in the spatial and/or time inversions. [25][26][27][28][29][30][31][32] In this research, we prove for the first time that the external stress can create new TWs and that these are also polar, as in the natural TW states. We think that this is not self-evident because the polarity of the TWs is induced by the shift of Ti atoms, 13 which could depend on the TW direction.…”

Harmonic Generation in Nanoscale Ferroelectric Films

“…Here we will be concerned with a theoretical model that takes into account the influence of surfaces on a ferroelectric film. There is also experimental evidence that indicates that size effects in ferroelectrics are observable Höchli & Rohrer, 1982;Kulkarni et al, 1988;Marquardt & Gleiter, 1982;Mishina et al, 2003;Scott & Araujo, 1989) ;more recently, the strong influence of boundaries on ferroelectric behaviour has been demonstrated (Li et al, 1996;1997).Due to the advent of ferroelectric random access memories (Scott, 1998) size effects in ferroelectric thin films are of increasing importance. This chapter shows how the Landau-Devonshire theory of ferroelectrics can be applied to thin films and how the dynamic response to incident electromagnetic radiation can be calculated.…”

Nonlinear-optical probing of nanosecond ferroelectric switching

“…The square root of the coherent SHG intensity is proportional to the in-plane volume domain fraction ͑and thus to the absolute value of ferroelectric polarization͒ 6,7 ͱI ͑ 2 ͒ϰ͉⌬F vx ͉ϭ͉P x ͉.…”

“…In this way optical second harmonic generation ͑SHG͒ gives direct information about domain orientation and switching. 6,7 However, applications of SHG to study domain orientation were limited to quasisteady state ͑low frequency͒ studies.…”

“…7. A transmission geometry was used and the angle of incidence was varied by rotating the sample around the vertical in-plane axis in the a͒ Author to whom correspondence should be addressed; electronic mail: theoras@sci.kun.nl APPLIED PHYSICS LETTERS VOLUME 83, NUMBER 12 22 SEPTEMBER 2003 range of Ϯ35°.…”