Experimental observation of the surface roughening transition in vapor phase growth

The surface roughening transition has been observed in growth from the vapor phase in both C₂Cl₆ and NH₄Cl. Both these materials are plastic crystals which have cubic structures and sublime at atmospheric pressure rather than melting. The surface roughening transition was detected by observing changes in the growth morphology in these two materials. In C₂Cl₆ the roughening transition is approximately at 100°C where the equilibrium vapor pressure is 40 mm, and in NH₄Cl it is at approximately 365°C and 3 atm pressure.