Epitaxial Growth of Bi(111) on Si(001)

Despite the large lattice misfit and different lattice symmetry, it is possible to grow smooth and almost defectfree bismuth (Bi) films on a Si(001) substrate. High resolution low-energy electron diffraction measurements have confirmed that the (111) orientation is the preferred direction of the growth. However, at low temperature and low coverage regime, rotationally disordered crystallites of (110) orientation are also observed. After the formation of a continuous layer at 5.6 bilayer (2.2 nm), the growth occurs in a bilayer-by-bilayer fashion at 150 K. The remaining lattice mismatch of 2.3% is accommodated by a periodic array of interfacial misfit dislocations, which gives rise to a periodic surface height undulation with sub-angstrom amplitude. Additional growth to the desired thickness caps the height undulation resulting in an atomically smooth surface (terrace size > 100 nm). The Bi(111) film is relaxed to bulk lattice constant and shows excellent crystalline quality with an abrupt interface to the Si substrate.