No abstract

No abstract

No abstract

No abstract

Epitaxial surface of NiSi2(001) studied with lowenergy electron diffraction and scanning tunneling microscopy Thinfilm crystallography using reflection highenergy electron diffraction ''rod intensity profiles'': Ni/Si(111) Submonolayer Ni deposits quenched from above 840°C produce an ''impurity stabilized'' 1ϫ1 phase, which scanning tunnel microscope observations reveal to be a 1ϫ1 lattice gas of ring clusters ͑RCs͒ together with Si adatoms in local 2ϫ2 domains. We call this phase 1ϫ1-RC. Real time low-energy electron microscopy observations show the following: terraces are covered with the 1ϫ1-RC phase except for narrow strips of 7ϫ7 along the top side of bilayer steps. The strip width decreases with increasing Ni coverage and increasing quench rate. Slow cooling results in clean 7ϫ7 only. Depositing Ni at 700°C causes the 1ϫ1-RC phase to expand, consuming 7ϫ7. At 720°C, the 1ϫ1-RC phase mixes with 7ϫ7 to cover the terraces uniformly. Depositing at 500°C instead causes formation of NiSi 2 islands in a matrix of clean 7ϫ7. These reactions are summarized in terms of a temperature versus coverage phase formation diagram.