Ferroelectric domains and material contrast down to a 5 nm lateral resolution on uniaxial ferroelectric triglycine sulphate crystals

We operate dynamic force microscopy (DFM) in non-contact mode under ultrahigh vacuum conditions in order to differentiate local chemical inhomogeneities from ferroelectric domains in bulk single crystals of triglycine sulphate (TGS), Individual layers of both mixed glycine and sulphate, and pure glycine ions are resolved resulting in a lateral material contrast of 5 nm and a sub-unit cell vertical contrast. The clue information is deduced when analysing the excitation amplitude A(exc) applied to the piezo shaker in constant amplitude DFM which is strongly affected either by the short-range chemical force or the longer range electrostatic contribution. The latter arises from the bound surface charge within individual ferroelectric domains and results in a long-range tip-sample interaction. From variation of the bias voltage applied to the TGS counter electrode we deduce the sign of the bound surface charge within each ferroelectric domain. Hence, domain walls that separate regions of antiparallel polarization are resolved down to a 9 nm domain wall width. Copyright (C) 1999 John Wiley & Sons, Ltd.