Surface morphology, chemical contrast, and ferroelectric domains in TGS bulk single crystals differentiated with UHV non-contact force microscopy

Ferroelectric bulk single crystals of tri-glycine sulphate (TGS) have been investigated in ultra-high vacuum (UHV) using dynamic force microscopy (DFM ) in the non-contact (nc) mode. Bath chemical contrast from different sub-u nit cell cleavage steps, and ferroelectric domains were differentiated by r ecording the variation in interaction force affecting the excitation amplit ude A(exc) applied to the piezo shaker in constant amplitude DFM. No chemic al difference was found for steps measuring half the unit cell height b, in contrast to b/4-steps where sulphate ions change the local short-range che mical forces. By varying the bias voltage applied to the TGS counter electr ode, the sign of bound surface charge within each ferroelectric domain was determined. Domain walls separating regions with antiparallel polarisation vectors are resolved down to a 9 nm domain wall width. Furthermore, we achi eved atomic resolution with nc-DFM on cleaved TGS samples indicating the mo noclinic unit cell at the ferroelectric sample surface with a = 1.0 +/- 0.0 5 nm, c = 0.55 +/- 0.05 nm, and beta = 107 +/- 3 degrees. (C) 1999 Elsevier Science B.V. All rights reserved.