Sputtering from a liquid Ga-In eutectic alloy

Angular distributions of Ga and In atoms sputtered from a liquid Ga-In eutectic alloy target have been measured for 3, 25, and 50 keV Ar^+ bombardment. Although the bulk composition of the alloy is 16.5 at.% In, thermodynamic surface segregation results in a surface monolayer of > 94 at.% In. A comparison of the measured sputtered-flux composition with the alloy surface composition profile indicates that the fraction of sputtered atoms originating in the first atomic layer, F_1, is ≈ 0.87 at 25 and 50 keV, and increases to 0.94 at 3 keV. Measurements of the secondary-ion flux for 25–250 keV Ar^+ bombardment indicate that F_1 is independent of projectile energy up to 250 keV, in agreement with the predictions of the collision-cascade model. The increase observed at 3 keV may be the result of a decrease in the average energy of recoil atoms participating in the collision cascades.