Surface Lab

studying the role of adsorbates on the
secondary emission properties of materials.

---

		In applications where the interaction of low energy ions with metallic surfaces is common, ion-induced secondary electron and ion emission is of fundamental importance. Perhaps the most common applications involve materials processing techniques where plasma-generated ions interact with surfaces exposed to the plasma. Secondary electrons and ions ejected from the surface may affect the equilibrium plasma characteristics such as species and charge densities, particle energy distributions, and the sheath thickness. The role of adsorbates in producing these secondary electrons and ions is of obvious importance, since most surfaces will have some form of (possibly time-dependent) adsorbate coverage.
Our earlier research concentrated on studies of low energy, ion-induced secondary electron emission and negative ion emission from aluminum [1,2], molybdenum [3] and stainless steel surfaces [4] upon which resides a known coverage of oxygen.      Recently, we have investigated low-energy bombardment of adsorbate-covered tungsten (W) [5] and silicon (Si(100)) [6] surfaces with positive sodium ions, measuring yields, kinetic energies, and masses of secondary negative ions and electrons. These measurements depend, in various degrees, on the incident ion energies and the adsorbate coverage (oxygen and/or chlorine) of the surface. A model used for previous substrates [3] was modified to describe emission from the O/W and Cl/W surfaces; a similar treatment of O/Si(100) surface is under development.
Currently, our experimental apparatus is undergoing a modernization process, whose purpose is to replace existing sodium gun by a more universal home-made discharge ion source similar to that used in our gas phase experiments. This will allow us to incorporate a wide variety of ions, both positive and negative, in our experiments. Its is a challenging task but successful complition of it will let us get our research even closer to real life industrial applications where ion-surface interactions involve rich variety of bombarding ions.      To learn about graduate research opportunities at AMO physics labs, please contact Dr. Champion or visit our laboratories in rooms 321 and 313 of Small Hall (Physics Department).

Up [1] J.C. Tucek, S.G. Walton, R.L. Champion, Phys. Rev. B 53 (1996) 14 127. [2] J.C. Tucek, R.L. Champion, Surf. Sci. 382 (1997) 137. [3] J.C. Tucek, S.G. Walton, R.L. Champion, Surf. Sci. 410 (1998) 258. [4] S.G. Walton, R.L. Champion, Y. Wang, J. Appl. Phys. 84 (1998) 1706. [5] W.S Vogan, S.G. Walton, R.L. Champion, Surf.Sci. 459 (2000) 14. [6] Manuscript in preparation. Front page - Introduction - Surface - Gas phase - Physics Dept.