Formation and healing of defects at theSi(111)7×7surface under low-energy ion bombardment

Abstract

We studied the formation and healing of adatom defects on a Si(111)7ϫ7 surface bombarded by 0.5-keV Ar ions. Scanning tunneling microscopy showed that adatoms were missing from the Si(111)7ϫ7 surface. Increasing the temperature during the bombardment increased the percentage of missing adatom sites. However, the percentage saturated at 400 K, then decreased with temperature. This temperature dependence was due to competition between the formation and healing of adatom defects; defect formation dominated at low temperatures, but was overcome by healing at high temperatures. We analyzed the temperature dependence using a rate equation for missing adatoms which included the temperature-independent sputtering and other temperature-dependent formation and healing processes. Activation energies of 0.29 and 0.39 eV were obtained for the temperature-dependent formation and the healing of adatom defects. The temperature-dependent formation was attributed to vacancy-adatom recombination, and the temperature-dependent healing was attributed to the interstitial atom-missing adatom site recombination. These vacancy and interstitial atoms were generated in the collision cascade under the surface. Some of them migrated to the surface and contributed to the temperature-dependent formation and healing of missing adatoms.

Defect formation inSi(111)7×7surfaces due to 200 eVAr+Ghose1, Robinson2, Averback3 2003Phys. Rev. B3010View full textAdd to dashboardCite

“…On a Si(111)7ϫ7 surface, bombardment with rare-gas ions has been reported to sputter surface adatoms in the low-energy range. [10][11][12][13] Our experiments found similar effects during irradiation with 200 eV Ar ϩ ion on Si(111)7ϫ7 surface at an incidence angle of 20°. Since the dimer, adatom, and stacking fault layers have unique signatures in the diffraction pattern, it is possible to measure the initial rate of erosion directly from the estimation of the missing atoms in each layer.…”

“…Previous work has involved mainly STM measurements made on a Si(111)7ϫ7 surface to study the surface defects formed by rare-gas ions in the energy ranges between 200 eV to 3 keV. [10][11][12][13][14] They observed that low energy (Ͻ500 eV) Ar or Xe ion bombardment on Si(111)7ϫ7 surface leads to clearly identified surface defects. These surface defects are populated by adatom vacancy regions, where adatoms have been removed by ion impact.…”

High-temperature real-time observation of surface defects induced by single ion irradiation using scanning-tunneling-microscope/ion-gun combined system

“…12 Our real-time high-temperature STM observations of the ion-irradiated surface enable us to monitor the sequential size changes of defects after ion irradiation. In their experiment, the surface defects shrink monotonically due to the atom supply from two-dimensional ͑2D͒ atom gas.…”

Influence of1×1defects on Schottky barrier height at theAg/Si(111)Hirayama1, Yamaguchi2, Ikezawa3 et al. 2002Phys. Rev. BSelf Cite9050View full textAdd to dashboardCite

“…14,15 The base pressure of the treatment and main chambers was less than 2 ϫ10 Ϫ8 Pa. The samples, with dimensions of 2.5 mm ϫ7.0 mmϫ0.2 mm, were cut from a low doped n-type Si͑111͒ wafer (ϭ1.5 ⍀ cm).…”