THE INFLUENCE OF OXIDIZED SI IMPURITIES ON THE PHASE-TRANSITIONS OF PT(110) SURFACES

Abstract

The Pt(110)1 x 2 and 1 x 4 reconstructions have been investigated by RHEED. From averaged rocking intensities it is concluded that the 1 x 4 reconstruction is due to a modified 1 x 2 structure. A periodic arrangement of larger microfacets than for 1 x 2 can be ruled out. While the clean surface always exhibits the 1 x 2 structure, AES measurements show that the 1 x 4 structure contains oxidized Si impurities. Like the 1 x 2 half arrow right over half arrow left 1 x 1 transition the 1 x 4 structure changes reversibly into a 1 x 1 structure when the crystal is heated to a certain critical temperature T(C). T(C) for 1 x 2 half arrow right over half arrow left 1 x 1 is 866 /- 15 K. For 1 x 4 half arrow right over half arrow left 1 x 1 T(C) increases considerably with the concentration of bound oxygen and is 1070 /- 15 K and 1140 /- 15 K for 1.4% and 2.3% O, respectively.