Scanning tunneling microscopy and ion channeling studies of thin Co films on bromine-treated Si(100) surfaces

Abstract

We report an attempt to see if one could prepare thin epitaxial silicide films on Si(100) substrates from a non-UHV technique. Growth and characterization of epitaxial cobalt silicide films has been studied. Thin films of Co (1.4-1.7 nm) are deposited at room temperature by evaporation on to bromine treated Si(100) substrate. Subsequently annealing was performed in vacuum at 440 degrees C, 570 degrees C and 680 degrees C. The morphology and the structure of the films were characterized by scanning tunneling microscopy (STM), Rutherford backscattering spectrometry (RBS) and ion channeling and scanning electron microscopy (SEM). The interface region was probed by STM through a large pinhole in the 680 degrees C annealed sample which revealed a flat region with oriented grains. Channeling measurements on the 570 degrees C and 680 degrees C annealed samples showed a reduction in the cobalt signal indicating crystalline growth of the silicide while the 440 degrees C annealed sample showed no reduction. Angular scans along various crystallographic directions for these samples showed shifts in the Co dips with respect to the substrate indicating a strained epitaxial film. Presence of strain even after island formation confirms that relief of misfit stress is not the driving force for pinhole formation and also implies that the thickness of the silicide films are within the reported critical thickness. (C) 2000 Elsevier Science B.V. All rights reserved.