Laser quenched and impurity induced metastable Si(111)1×1 surfaces

Abstract
Metastable rearrangements of the surface atoms yielding a 1×1 LEED pattern can be obtained on Si (111) either by quenching from high temperatures or/and by impurity stabilization. In particular, laser annealing produces clean 1×1 structures with no LEED evidence for long-range reconstruction. We have investigated by UV photoemission and LEED laser-annealed flat and vicinal Si (111) surfaces. We find that, for 10-ns pulses (0.4 J/cm2) at λ = 0.53 μ, the surface is mostly disordered (<16 Å domains) with possibly a local buckling reconstruction. For 15-ns pulses (2 J/cm2) at λ = 0.69 μ, the surface is still disordered with a 7×7-like reconstruction. Since different laser parameters can alter the regrowth velocity by over a factor of two, kinetic parameters were determined from LEED studies of vicinal surfaces. There is evidence that different amounts of long-range order can be obtained by varying regrowth velocities in the range 2 to 7 m/s. Impurity stabilized 1×1 surfaces also involve a certain amount of disorder. The relevance of the study of 1×1 surfaces to the understanding of the stable reconstruction on Si (111) is discussed.