Decoding homophilic recognition specificity of Dscam, a neuronal receptor with thousands isoforms
J.-H. Wang, Qian Chen, Rob Meijers, Dietmar Schmucker, J. Liu, H. Zhang · Acta Crystallographica Section A Foundations of Crystallography · 2008
Dislocations near surface of 4H-SiC were observed using synchrotron radiation topography in the Bragg case with grazingincidence geometry.Figure is an image of basal-plane dislocation half-loop at g=11-28, λ=0.15nm on Si-face.The (0001) plane is tilted towards the [-1-120] direction by 8 degrees from the surface.In this condition, lattice defects within 10 µm depth are observed.Along this dislocation line, bright contrast at A, dark and bright asymmetric line at B, and dark contrast at C are observed.Absence in contrast can be seen at B at g=1-108, and so that B is a screw dislocation part.We have observed migrations of dark dislocations in specimens after forward-bias degradation effect, in which Si-core dislocations are known to move.Thus we concluded that C is Si-core, A is C-core edge dislocation, and the Burgers vector is 1/3[-1-120].The observed dark and bright contrast is discussed to be similar effect described by Ando and Kato (1970).By applying this rule we could identify uniquely 6 different Burgers vectors for all basal-plane dislocations and threading edge dislocations at only one diffraction condition.