Experimental Investigations and Molecular Dynamics Simulations of Radiation Induced Surface Damage
Final rept. 15 Aug 1991-14 Aug 1993
NORTHWESTERN UNIV EVANSTON IL
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The research is part of a several year study of the electron stimulated desorption ESD behavior of transition metal oxides. The original objective of this research was the development and implementation of an ESD O atom source to be used in Low Earth Orbital LEO simulations of materials damage. Though the desorption of neutral particles has been widely postulated, most of the ESD results found in the literature are measurements of ejected ions. The principal reason for this is the ease of ion detection and the inherently low sensitivity of detectors to neutral particles. Most information pertaining to the relative abundance of neutral versus ion desorption is the result of indirect measurements. Despite extensive experimentation including the application of resonant enhanced multiphoton ionization for the selective detection of atomic oxygen the production of atomic oxygen via ESD was never detected. From careful calibration experiments the upper limit to the neutral to ion yield, 00, by ESD was calculated to be 10. From electron microscopy studies of both the reconstructed Ir001 and Si001 surfaces, the controversy between the existing models in literature - 0.016 nm for the lr001-5x1 models and -0.005 nm for the Si001-2x1 models could be resolved for the first time using a combination of UHV-TED and UHV-HREM techniques.
- Radiation and Nuclear Chemistry
- Atomic and Molecular Physics and Spectroscopy