Surface Roughening and Quasi-Liquid Layer

Publisher Summary The theoretically predicted roughening temperatures of close-packed crystal faces significantly exceed the melting point of the crystal. However, the experimental results show that for some substances the surface roughening occurs below the melting point, the roughening temperature being 2-4 times lower than the calculated values. A model, proposed in this chapter, according to which the roughening occurs on crysta1-quasi-1iquid layer interface, aims at obtaining the roughening temperature in correspondence with the experimental results. A necessary condition for the existence of thin liquid (quasi-liquid) layer on a crystal face is the complete wetting of the face by its own melt. The equilibrium thickness d of the layer is an increasing function of the temperature. When increasing d the energy L needed for transition of an atom from the crystal surface into the quasi-liquid layer decreases and hence the roughening temperature decreases. In order to determine the roughening temperature Jackson's criterion is used and derived in the chapter.