Ion bombardment of the Al (111) surface induces growth rather than erosion (for small ion fluences), see experiments by Michely. This is due to the formation of the local melting of the Al crystal. As a consequence, Al atoms flow on the surface where they remain in the form of adatom islands. Deeper in the crystal, vacancies are frozen in.
Below we show mpeg movies of some selected events. The atoms are colored according to their "temperature" - i.e. essentially their kinetic energy - in units of the Al melting temperature, 933.6 K.
For Xe bombardment, the swelling of the surface (growth) is strongest.
Movie (~ 1.3 MB) A deep spike forms, leaving 11 adatoms on the surface after cooling. This is a representative event.
Movie (~ 1.3 MB) A low adatom-yield event: Only 3 adatoms are formed.
Movie (~ 1.3 MB) high adatom-yield event: 16 adatoms are formed. The region below them appears strongly disordered (amorphized).
Movie (~ 1.3 MB) An even higher adatom-yield event with 22 adatoms.
For Ne bombardment, the energy density delivered in the solid is lower; the spike cools faster. Consequently, surface swelling is not as pronounced.
Movie (~ 1.3 MB) The spike loses connection to the surface and cools fast. Only 3 adatoms are formed.
Movie (~ 1.3 MB) Note the reflection of the projectile (large sphere).
Movie (~ 1.3 MB) High-yield event, showing similarity to Xe bombardment. 10 adatoms are formed.
last reviewed: Wednesday, 07.03.2001
last updated: Wednesday, 07.03.2001