Edge melting of the Ge(111) surface studied by scanning tunneling microscopy

The scanning tunneling microscope (STM) is used to study the disordering of the Ge(111)c(2×8) surface, at temperatures in the range 150-350°C. The disorder occurs by the diffusion of surface adatoms in the 〈011〉 directions. Disordered regions form at domain boundaries of the c(2×8) structure, and grow in size continuously with temperature until the entire surface becomes disordered at about 300°C. This order-disorder transition is identified as an example of premelting in two dimensions, i.e. edge melting. Thus, the phase transition would be first-order for an infinite size c(2×8) domain, but is actually continuous due to the occurrence of premelting at the domain boundaries. © 1992.