ABSTRACT Proposal Number: CTS-9610123 Principal Investigator: James R. Engstrom Institution: Cornell University Probes for an existing UHV reactor dedicated to semiconductor thin-film deposition will be purchased. They will include: a quadrupole mass spectrometer with molecular-beam compatible cross-beam ionizer and negative or positive ion detection capability: a translation stage for sample positioning; a refrigeration trap for the quadrupole mass spectrometer; a lock-in amplifier for reverse-view LEED or retarding-field Auger spectroscopy; and accessories.