Crystallographic orientation dependence of SEM contrast revealed by SiC polytypes

Abstract

In low energy scanning electron microscope (SEM) with primary electron energy less than 1.0 keV, the dependence of SEM contrast on crystallographic orientation within a range of 1.0 nm in depth has been investigated by utilizing 4H-SiC (0001) as a standard sample having a definitive electron penetration depth marker layer at hexagonal sites. Reflecting the difference of the direction of topmost two Si-C bilayers stacking sequence (0.50 nm in depth), clear bright and dark SEM contrast has been observed by adjusting the sample tilting and rotation angles by a conventional Everhart–Thornley type in-chamber detector. It is revealed that the brighter signal emission arises when the incident primary electron beam direction is almost parallel to the topmost stacking sequence direction. This angular coincidence was verified separately by correlating low energy SEM contrast from 3C-SiC (111) of no hexagonal sites with its electron back scattered diffraction pattern for identifying stacking sequence direction. The obtained results suggest a potential of low energy electron to characterize the crystallographic orientation just beneath the surface without using any special detector.

Research Update: Focused ion beam direct writing of magnetic patterns with controlled structural and magnetic properties

“…Inside of each triangular domain we can observe an additional texture. Unfortunately, the SEM observation does not allow to extract any quantitative information about the crystallography of the areas with different contrast 18 .…”

“…Although the sample surface after transformation was perfectly flat, by using an electron energy of 5 keV and a conventional Everhart-Thornley (SE) detector we were able to observe a clear contrast between irradiated and non-irradiated areas. The contrast was reversing from dark to white and back upon tilting the sample ±10° from the normal and also upon rotation (with 6-fold symmetry in bcc areas and 8-fold symmetry in fcc areas), which points to its crystallographic origin 18 . This crystallographic contrast cannot be fully quantified, but it is sufficient to image the difference between untransformed fcc Fe and transformed bcc Fe areas and also to distinguish different orientations of bcc domains after the transformation.…”

Nucleation Control of 3C-SiC Induced by the Spiral Structure of 6H-SiC

“…A low acceleration voltage of 1 kV with an inclined angle of 30°to the ⟨11̅ 00⟩ direction was used to perform surface-sensitive observations by using the surface channeling effect. 27 Step height measurements were also carried out for the substrate after dissolution using an atomic force microscope (AFM, L-traceII, Hitachi High-Technologies Corporation). In addition, the crystal orientation of the islands of 3C-SiC was determined via electron backscatter diffraction (EBSD) analysis (Nordlys Nano, Oxford Instruments) with an accelerating voltage of 5 kV.…”

“…The surface structure of the substrate was evaluated via field-emission scanning electron microscopy (SEM, JSM-7800F, JEOL Ltd.) after the dissolution process and then after the nucleation process. A low acceleration voltage of 1 kV with an inclined angle of 30° to the ⟨11̅00⟩ direction was used to perform surface-sensitive observations by using the surface channeling effect . Step height measurements were also carried out for the substrate after dissolution using an atomic force microscope (AFM, L-traceII, Hitachi High-Technologies Corporation).…”

Interactions Between Epitaxial Graphene Grown on the Si- and C-Faces of 4H-SiC Investigated Using Raman Imaging and Tip-Enhanced Raman Scattering

“…5 Growth of the epitaxial graphene can be induced by Si sublimation from annealed SiC, which preferentially occurs over C sublimation. 1–12 On the Si(0001)-face, several graphene layers can be formed because the Si sublimation is suppressed by a (6√3 × 6√3) R 30° buffer and an AB (or Bernal) stacking layer. 3,4 In this manner, the number of graphene layers can be controlled.…”