SCANNING TUNNELING MICROSCOPE OBSERVATION OF SURFACE-MORPHOLOGY OF SILICON STEEL SHEETS

Scanning tunneling microscope (STM) was applied to the investigation o f surface morphology of polycrystalline silicon steel sheets. Polished 3%Si-1%Mn-0.02%Al-0.05%C specimens were annealed at 1300 degrees C fo r 10 min in a vacuum of 10(-4) Pa. The detailed observations reveal th at the fine facet structure is formed on the near (001) surface of the alpha-phase grains of 100-500 mu m in diameter. The terrace width and the step height of facets are determined by the misorientation angle of the grains from the [001] orientation. These results suggest that t he (001) surface of the silicon steel sheets can be covered with a thi n iron oxide film with the orientation relationship of alpha(001)paral lel to FeO(001) and alpha[100]parallel to FeO[110] or alpha(001)parall el to Fe3O4(001) and alpha[100]parallel to Fe3O4[110], in keeping with the facet that the observed minimum step height of the terrace corres ponds to the (001) lattice spacing of these oxides. The change of face t structures by lowering annealing temperature will also be discussed.