Abstract

The atomic force microscope (AFM) was used to image {001} surface microtopography and molecular-scale structure of two natural specular hematite samples. Topographic images in air and under H2O showed that although the surface is atomically flat in some aieas, pits and steps are abundant. Molecular-scale resolution in air showed a hexagonal array of peaks with ~5-Å spacing, representing surface Fe atoms with coordinated sorbates. Comparison with scanning-tunneling microscope (STM) images_of the {001} surface-Fe-atom array in air, which ilso had hexagonal symmetry and ~5-Å spacing, showed that the scanning probe microscopes can produce similar high-resolution images of hematite even though they rely on different physical operating mechanisms. Results of these studies indicate that for conducting or semiconducting minerals, a combination of scanning-tunneling and atomic-force microscopy permits direct, in situ analysis of mineral surface structure and microtopography.

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