Segregation phenomena on PtxNi1-x low index single crystal surfaces studied by STM

Surface segregation changes the composition of alloy surfaces. It influences both the geometrical and the chemical structure of the surface. In this paper segregation phenomena are shown for low index single crystal surfaces of different PtNi alloys which can be seen only by scanning tunneling microscopy (STM). STM experiments performed with atomic resolution revealed the existence of subsurface dislocation networks. A closer study of the conditions of their existence allowed us to understand the effects of preferential sputtering and annealing on the segregation behavior (i.e. building up a rather stable altered layer and its disappearance only at elevated temperatures). In addition, local chemical ordering in small domains and shifted row reconstructions with a large and varying periodicity (i.e. phenomena that are hardly seen by other methods like e.g. LEED) have been observed.