Metastable and equilibrium structures on Pt3Sn(001) studied by STM, RHEED,LEED, and AES

After sputtering and moderate annealing (600 K) the Pt3Sn(001) surface show s a c(2X2)-LEED pattern with streaky facet spots. The scanning tunneling mi croscopy (STM) images show pyramidal features that mainly consist of (102) facets, in addition to flat parts between and on top of the pyramids. On th e hat parts the dominating feature are triple atomic rows, which probably c onsist of Pt. According to Auger electron spectroscopy the Sn surface conce ntration is seduced due to preferential sputtering. Annealing at 1000 K res tores the Sn surface concentration and leads to an improved c(2X2)-LEED pat tern with no facet spots. With the STM the disappearance of the pyramids an d the formation of large flat terraces with added single atomic rows along the [100] and [010] surface directions is observed. All steps found are dou ble steps, indicating a strict termination with the mixed Pt/Sn layer. Chem ical contrast between Pt and Sn atoms is observed. [S0163-1829(99)09627-7].