Abstract
Step motions on NaCl (001) surface were monitored by atomic force microscopic observation following heat treatments of up to 973 K. Thermally activated step motion was first recognized at 723 K. At that temperature, monatomic steps with positive curvature retreated decreasing step lengths, while multi-atomic steps remained intact.Monatomic steps with negative curvature were segmented into non-polar steps, in spite of an increase in the step lengths. The segmented steps became smooth again at 773 K. Atomic motion was restricted on the same terraces up to this temperature. At 873 K, atomic motion from upper to lower terraces was enabled and decomposition of multi atomic steps into monatomic steps was observed, which was interpreted as roughening transition. Mesoscopically, the surface became smoother in 3-dimensions. Although the step energy decreased with an increase in temperature, a preference for electrically neutral steps remained. Complete roughening of the surface due to surface melting was observed after heating to 973 K.
