It was noted that  in situ  scanning tunnelling microscopic observations of (111) quenched surfaces at 550 to 700C had revealed that isolated 7 x 7 domains nucleated or annihilated with a single stacking fault triangle as a building unit, and that there existed a critical nucleus size for 7 x 7 domain growth.

T.Hoshino, K.Kokubun, H.Fujiwara, K.Kumamoto, T.Ishimaru, I.Ohdomari: Physical Review Letters, 1995, 75[12], 2372-5