Biassed secondary electron imaging of monatomic surface steps on vicinal Si(100) in a UHV STEM

Biassed secondary electron (b-SE) SEM images of steps on Si(100) surfaces misoriented 1° towards 〈110〉 have been obtained using a number of imaging geometries including normal incidence. The periodicity of the regularly spaced steps unambiguously identifies these as single-atom-high steps. High-efficiency secondary electron collection from the input surface of the sample makes it possible to obtain images of low contrast features on low-atomic-number samples in UHV. Simple topography is shown to be a likely mechanism for the contrast observed in the digitally acquired b-SE images. Images of step pinning at refractory particles during surface sublimation identify the up-step direction and are similar to those obtained by other surface microscopic techniques.