The kinetics of vacancy diffusion on (111) surfaces was studied by means of scanning reflection electron microscopy. Two types of layer-by-layer etching were observed during 500eV Ar-ion bombardment at high substrate temperatures. One was step-retreat (reversal of step-flow growth), and the other was 2-dimensional vacancy island nucleation. The results showed that vacancies, which were created by low-energy ion impact, diffused on the surfaces and were annihilated at step edges. The vacancy diffusion kinetics on the surface were also examined by means of scanning reflection electron microscopy. An activation energy of 3.0eV was deduced from the vacancy diffusion length, as estimated from the width of denuded zones. The latter were created on both sides of an atomic step, by heating, after the introduction of vacancies by ion bombardment at room temperature. The results indicated that the vacancy diffusion kinetics were dominated by mono-vacancy formation and diffusion. These processes required thermal excitation in order to overcome the potential barrier to the surface diffusion of adatoms, and to overcome the lateral binding energy and thus release adatoms from the step edges.
Kinetics of Vacancy Diffusion on Si(111) Surfaces Studied by Scanning Reflection Electron Microscopy. H.Watanabe, M.Ichikawa: Physical Review B, 1996, 54[8], 5574-80
Table 112
Diffusion of Si over Si Surface Terraces
Terrace | Temperature (C) | D (cm2/s) |
2 x 1 | 600 | 2.0 x 10-10 |
2 x 1 | 650 | 7.6 x 10-10 |
2 x 1 | 700 | 2.3 x 10-9 |
2 x 1 | 750 | 5.1 x 10-9 |
2 x 1 | 800 | 1.2 x 10-8 |
2 x 1 | 850 | 2.6 x 10-8 |
2 x 1 | 900 | 5.3 x 10-8 |
1 x 2 | 600 | 3.2 x 10-10 |
1 x 2 | 650 | 9.0 x 10-10 |
1 x 2 | 700 | 2.6 x 10-9 |
1 x 2 | 750 | 6.5 x 10-9 |
1 x 2 | 800 | 1.5 x 10-8 |
1 x 2 | 850 | 3.0 x 10-8 |
1 x 2 | 900 | 5.6 x 10-8 |