Surface structures of scandium silicides grown on Si(1 1 1) studied by STM, AFM and electron diffraction

We have investigated the formation of ScSi2−x on Si(1 1 1) using in situ scanning tunneling microscopy (STM), electron diffraction (RHEED, LEED) and ex situ atomic force microscopy (AFM). In the temperature range between 500 and 600 °C, a variety of structures has been observed in STM including domains of anisotropic rod-shaped islands along 〈 1 ¯ 1 0 〉 directions, exhibiting mainly (2 × n) (n = 1–3) periodicity, and large patches of two-dimensional p(1 × 1), p(3 × 1) and (√3 × √3)R30°. Thicker layers show large flat terraces with a strained c(2 × 2) surface structure, which has been confirmed by LEED. At 900–920 °C, large strained two-dimensional ScSi1.7 islands are formed where strain is relieved by the formation of line defects. RHEED patterns taken at different temperatures and growth stages show very interesting features, which have been correlated to the silicide structures observed in STM.