The defect structure at the growth front of 4H-SiC boules grown using the physical vapor transport (PVT) method has been investigated using high resolution x-ray diffraction and x-ray topography. The crystal parameters such as the c -lattice constant exhibited characteristic variations across the growth front, which appeared to be caused by variation in surface morphology of the as-grown surface of the boules rather than the defect structure underneath the surface. X-ray topography also revealed that basal plane dislocations are hardly nucleated at the growth front during PVT growth of 4H-SiC crystals.
The wide (0001) terrace formation due to step bunching on a vicinal 4H-SiC (0001) epitaxial layer surface was investigated using low-energy electron channeling contrast (LE-ECC) imaging and atomic force microscopy. LE-ECC imaging revealed that step bunching resulted in the formation of wide atomically-flat (∼200 nm) (0001) terraces on the surface, and the terraces tended to form in pairs. Terraces in a pair had almost the same width and often showed the same LE-ECC; moreover, the contrast of the two terraces, either bright or dark, appeared to be determined by the orthogonal misorientation of substrates. On the basis of these results, the formation mechanism of the paired terraces with the same LE-ECC on a vicinal 4H-SiC (0001) surface is discussed herein.
Step bunching on a vicinal 4H-SiC (0001) epitaxial layer surface was investigated using low-voltage electron scanning microscopy (LVSEM) and electron channeling contrast (ECC) imaging. LVSEM observations revealed that the step bunching resulted in the formation of atomically flat wide (~250 nm) terraces on the surface, and the terraces tended to form in pairs. The two terraces in paired terraces often showed the same electron channeling contrast as each other, and the contrast of the two terraces, either bright or dark, appeared to be determined by the orthogonal misorientation of substrates. On the basis of these results, the formation mechanism of the step-bunched structure on a vicinal 4H-SiC (0001) surface is discussed.
The surgical treatment of cavernous malformation (CM) in the middle cerebellar peduncle is often very challenging due to its anatomical difficulties and the potential surgical risks. We successfully performed the removal of left middle cerebellar peduncle CM with a developmental venous anomaly (DVA) applying the cerebellomedullary fissure (CMF) approach, and herein we will discuss the outline of this experience and our surgical procedure accompanied by a surgical video. A 76 year old man was transferred to our hospital with a left cerebellar ataxia. He had a history of at least 3 episodes of CM hemorrhage in the past 2 years, and the preoperative image showed a left middle cerebellar peduncle hemorrhage just beside the fourth ventricle. Angiography showed the association of a DVA. Considering the location of the CM, we considered CMF approach to be the most effective procedure to achieve the removal of the CM without incising any normal brain structures. By completely opening the CMF up to the lateral recess of the fourth ventricle and incising the telovelar junction, we could realize a sufficient surgical corridor and maneuverability for the middle cerebellar peduncle lesion without any hindering and darkening of the microscopic view. Postoperative images showed the complete resection of the CM and the DVA remained intact. This report introduced the actual surgical procedure for the treatment of middle cerebellar peduncle CM with the CMF approach. The surgical videos provided here will help you understand the step-by-step surgical procedures required and the actual maneuverability for this approach.
