AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA5
Consequences of Electron Irradiation of Hydrated Crystals: Self Organized Nanometer Cone Formation

Tuesday, October 3, 2000, 3:20 pm, Room 209

Session: Stimulated Processes and Excitations
Presenter: S.C. Langford, Washington State University
Authors: S.C. Langford, Washington State University
M. Dawes, Washington State University
J.T. Dickinson, Washington State University
Correspondent: Click to Email
Radiation effects on hydrated single crystals are poorly understood. We find that dense arrays of conical structures, with aspect ratios on the order of 200, are produced by exposing single crystal brushite (CaHPO@sub4@.2H@sub2@O) to energetic electrons (2 keV). By exposing thin brushite platelets bonded to the surface of a metal heater to energetic electrons, the surface temperature can be controlled independently of electron dose. This work shows that cone formation requires surface temperatures of 400-600 @degree@C. The cones are directed along the direction of the incident electrons, and often display a cap-like structure that may play a role in cone production. Cone formation is accompanied by the development of a distinctive orange luminescence during electron irradiation, presumable due to electronic defects. The waters of hydration in this material may play a role in cone development by enhancing ion mobility in the heated material. Characterization of surfaces covered with conical structures has been performed by TEM, EPS, and IR spectroscopy.