It was recalled that diffraction data indicated that (110)-(1 x 2), which was missing-row reconstructed at 300K, underwent consecutive 2-phase transitions during heating. One of these was an Ising transition at about 650K, and the other was a 3-dimensional roughening transition at about 700K. The use of real-space atomic-scale resolution investigations, involving temperature-variable scanning tunnelling microscopy, revealed that the Ising transition was due to antiphase domains which developed during the 2-dimensional roughening of 1 x 3 steps. It was found that the missing-row configuration of interior terrace regions remained completely stable up to the 3-dimensional roughening temperature. This ruled out the occurrence of an order-disorder transition via lattice-gas formation.

M.Sturmat, R.Koch, K.H.Rieder: Physical Review Letters, 1996, 77[25], 5071-4