LOSS OF MATERIAL FROM GA-IN LIQUID SURFACE DURING BOMBARDMENT BY HYPERTHERMAL TA, PT AND AU ATOMS

We have investigated the loss of incident atoms and of substrate atoms from the surface of the liquid Ga-In eutectic alloy during bombardment of the surface with hyperthermal Ta, Pt and Au atoms. Hyperthermal atoms were produced by sputtering solid metallic targets positioned directly above the liquid Ga-In surface. By analyzing material deposited on graphite collector surfaces which surrounded the liquid alloy during bombardment, angular distributions were determined for atoms leaving the liquid surface as a result of the bombardment. For all three species of incident atoms, we detected Ga and In as well as the primary sputtered species on the collectors. The angular distributions for the primary sputtered species were strongly peaked in a near-normal direction consistent with direct reflection from the liquid surface. In all cases, we observed angular distributions for the Ga which included a broad peak, centered near the surface normal, although not at the same angle as the maximum for the incident species. Such a broad distribution is consistent with secondary sputtering of the liquid surface by the incoming atoms. The distribution of indium atoms is also suggestive of sputtering. However, we observed significant asymmetry in the In distributions which may be correlated with the angular distributions for the incident species. Our results support previous data indicating that surface sputtering (or re-sputtering) and direct reflection of primary sputtered atoms are significant mechanisms for the loss of material from surfaces during hyperthermal processes such as sputter deposition.