AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2+EM-TuA

Paper SS2+EM-TuA5
Microscopy of Si(001) Surface Defects Produced by keV He Ion Irradiation at Low Temperatures

Tuesday, October 26, 1999, 3:20 pm, Room 6C

Session: Semiconductor Surface Chemistry
Presenter: D.G. Cahill, University of Illinois, Urbana-Champaign
Authors: K. Kyuno, University of Illinois, Urbana-Champaign
D.G. Cahill, University of Illinois, Urbana-Champaign
R.S. Averback, University of Illinois, Urbana-Champaign
J. Tarus, University of Helsinki, Finland
K. Nordlund, University of Helsinki, Finland
Correspondent: Click to Email
The interactions of bulk point defects (interstitials and vacancies) with silicon surfaces influences microstructures and dopant profiles created by low-energy ion implantation. To gain insight on the migration of ion-induced defects and their interactions with surfaces, we use variable temperature scanning tunneling microscopy (STM) to measure the areal density of surface defects created by 5 keV He ion irradiation of Si(001) at low temperatures. Samples are irradiated to a dose of 1.7 and 3.4x10@super 13@ ions cm@super -2@ at 80, 130, 180, and 294 K, and imaged at the same temperature. Because of the background density of surface vacancies, we focus our analysis of the STM images on the densities of adatoms, dimers, and clusters formed by the ion bombardment. The density of these protrusions at 80 and 130 K is approximately linear in dose, independent of temperature, and in reasonable agreement with our molecular dynamics calculations of surface defect concentrations. At 180 K, the measured density of protrusions is enhanced by a factor of ~3; we interpret this result in terms of the onset of bulk defect migration. Surprisingly, the Si(001) surface appears to be a relatively inefficient trap for bulk defects under our experimental conditions; our results can be explained by the migration and trapping of defects formed within less than 1 nm of the surface.