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The angular distribution of atoms sputtered from a GaIn eutectic alloy target

1989; Elsevier BV; Volume: 36; Issue: 4 Linguagem: Inglês

10.1016/0168-583x(89)90342-x

1872-9584

Kevin M. Hubbard, Robert A. Weller, D.L. Weathers, T.A. Tombrello,

Electron and X-Ray Spectroscopy Techniques

Angular distributions of sputtered atoms have been obtained for 3, 25, and 50 keV Ar+ bombardment of a liquid GaIn eutectic alloy target. Sputtered material was collected on graphite foils which were subsequently analyzed by Rutherford backscattering spectroscopy, and the resulting distributions were fit by a functional form, N (θ) α. cosnθ. For each energy, the angular distribution of sputtered In atoms was overcosine, with nIn ≈ 1.8 ±0.1. The distributions of the sputtered Ga atoms were sharper, varying from nGa ≈ 3.2 ± 0.2 at 25 and 50 keV, to nGa = 4.9 ± 0.3 at 3 keV. A comparison of the sputtered flux composition with the alloy surface composition profile gives F1, the fraction of sputtered atoms originating from the first atomic layer. The fraction was found to be f1 = 0.87 ± 0.01 for 25 and 50 keV bombardment, and increased to 0.94 ± 0.01 at 3 keV. The variations of nga, and F1 with projectile energy may be the result of a decrease in the average recoil-atom energy for the 3 keV bombardment. The large values found for F1 support a prediction that the sputtered-atom escape depth is determined by the elastic-collision mean free path of recoil atoms.