Measurements on highly oriented pyrolytic graphite (HOPG) have been performed with a high-resolution spot profile low-energy electron diffraction system (SPA-LEED). It is demonstrated that HOPG samples show a wide spread in out-of-plane orientations of the crystallites at the surface. This may cause asymmetric features in scanning tunneling microscope images. These misorientations and not the crystallite sizes determine the widths of the observed diffraction rings. The results of SPA-LEED and STM are found to be complementary.
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