US-Federal Republic of Germany Cooperative Research:        Direct Imaging of Surface Phase Separation Using LEERM
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{'SignBlockName': 'Christine French', 'PO_EMAI': None, 'PO_PHON': None}
This award supports Professor Ellen D. Williams and Dr.                         Raymond Phanuef of the University of Maryland to collaborate                    with Professor Ernst G. Bauer of the Physics Institute of                       the Technical University of Clausthal, Federal Republic of                      Germany, in a study of phase separation of silicon surfaces.                    At the University of Maryland, a phase separation of                            surfaces vicinal to Si(111) has been discovered and                             characterized using Low Energy Electron Diffraction (LEED).                     A thermodynamical description of the transition has been                        developed, but major questions about the mechanisms of mass                     transport remain.  At the Technical University of Clausthal,                    a remarkable new instrument called the Low-Energy Electron                      Reflection Microscope (LEERM) has been developed.  This                         instrument can be used to image surfaces in real time with                      better than 200 angstroms resolution.  It is currently the                      only such instrument in the world.  Experiments previously                      performed using LEED at the University of Maryland will be                      repeated using the LEERM at Clausthal.  Silicon surfaces                        will be imaged at the temperature of the transition so that                     the motion of the surface steps involved in the phase                           separation can be observed directly.  The results will be                       used to test theoretical models for step wandering, surface                     self-diffusion and the energetics of the Si(111) surface                        reconstruction.                                                                                                                                                 Faceting is a widespread phenomenon in which a surface                          rearranges via large scale mass transport to form planes of                     different orientations.  The occurrence of faceting is                          important in catalysts, where it is linked to catalyst                          deactivation and also possibly to oscillations in reaction                      ranges.  Faceting may also cause the smoothness of epitaxial                    interfaces to be degraded during growth.  Finally, the                          mechanisms of faceting may be important in understanding                        surface roughness related to adhesion and lubrication.                          Little progress has been made in developing a detailed                          understanding of faceting in the past 20 years due to lack                      of experimental data to support theoretical speculations.                       This work proposes use of real time imaging to follow                           surface-faceting under well controlled conditions.
[{'FirstName': 'Ellen', 'LastName': 'Williams', 'PI_MID_INIT': 'D', 'PI_SUFX_NAME': None, 'PI_FULL_NAME': 'Ellen D Williams', 'EmailAddress': 'edw@physics.umd.edu', 'NSF_ID': '000332396', 'StartDate': '07/01/1989', 'EndDate': None, 'RoleCode': 'Principal Investigator'}, {'FirstName': 'Raymond', 'LastName': 'Phaneuf', 'PI_MID_INIT': 'J', 'PI_SUFX_NAME': None, 'PI_FULL_NAME': 'Raymond J Phaneuf', 'EmailAddress': 'phaneuf@umd.edu', 'NSF_ID': '000103118', 'StartDate': '07/01/1989', 'EndDate': None, 'RoleCode': 'Co-Principal Investigator'}]
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{'Code': '5936', 'Text': 'GERMANY (F.R.G.)'}
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