Unusual growth phenomena of group III and group V elements on Si(1 1 1) and Ge(1 1 1) surfaces

The surface reconstructions and growth of thallium overlayers on Si(1 1 1) 7×7 and the adsorption geometry of phosphorus on Si(1 1 1) 7×7 and Ge(1 1 1) c(2×8) surfaces have been examined by STM and are discussed in terms of the interplay of adsorbate-induced surface strain and adsorbate–substrate bond energy effects. The adsorption of Tl layers at room temperature maintains the Si (7×7) reconstruction, whereas at elevated temperature, a pseudomorphic (1×1)-Tl overlayer is formed. The growth of Tl multilayers on these two Tl terminated monolayer surfaces, the Si-“(7×7)”-Tl and Si-(1×1)-Tl, yields very different 3D Tl island shapes, thus illustrating the importance of the substrate surface potential on the growth mode. Phosphorus on Si(1 1 1) is adsorbed in a substitutional adsorption geometry in a discommensurate domain wall phase, whereas on Ge(1 1 1) it forms P trimer units in a local (√3×√3)R30° structure.