A model for ion-bombardment induced erosion enhancement with target temperature in liquid lithium

Abstract

Sputtering does not vary strongly with target temperature for most solid materials. Sputtering yield measurements of liquid lithium self-sputtering for energies of 200–1000eV at oblique incidence, however, show an enhancement near an order of magnitude as the temperature of the liquid lithium target is increased from near its melting point at 473K up to about 690K (∼1.5Tm) after accounting for thermal evaporation. A new model that couples both the near-surface cascade of the hot liquid metal and the effect of multiple interaction mechanisms on the binding of the emitted particle explains this anomalous erosion enhancement with target temperature. The model, has been validated using a new hybrid computational tool named MD-TRIM (molecular dynamics in transport of ions in matter), at 473K and 653K and compared to experimental data. MD-TRIM consists of molecular dynamics and binary collision approximation (BCA) codes, TRIM (transport of ions in matter). The MD-TRIM code was designed to aid in understanding erosion enhancement mechanisms of lithium self-bombardment sputtering at low bombarding energies with a rise in target temperature. MD calculations alone do not show the sputtering enhancement with temperature rise due to an inadequate surface potential model.