Atomic Structure of Hexagonal 6H– and 3C–SiC Surfaces

Abstract

The crystallography of hexagonal SiC surfaces prepared ex situ by chemical methods was investigated by low energy electron diffraction (LEED) structure analysis. The surface morphology was analyzed by considering mixtures of domains with different surface layer stacking geometries. On the 6H–SiC(0001) surface ABCACB stacking is the dominating termination, covering about 80% of the surface. On [Formula: see text] all three possible surface stacking sequences are present. The (111) surface of a 3C–SiC film sample shows linear stacking of layers with only one domain orientation present. In contrast to the carbon-terminated 6H sample, the silicon-terminated surfaces are covered by an oxygen layer with the adatoms bound on top of silicon.

Novel Reconstruction Mechanism for Dangling-Bond Minimization: Combined Method Surface Structure Determination ofSiC(111)-(3×3)

“…The topmost adatom and beam splitter (light gray sphere) is surrounded by a trimer, thus constituting a tetrahedral adatom cluster. The adcluster is oriented opposite to the substrate orientation (local stacking fault) as determined by comparison with a previous LEED analysis of the ͑131͒ phase on the same sample [7,8,28]. Two atoms are visible underneath the adatom which can be attributed to the silicon adlayer and the topmost atom of the SiC bulk, respectively, in correspondence to the Kulakov model [16].…”

“…Hereby, the polytype reproduction was mediated by diffusion of incoming particles to steps where the stacking sequence is exposed due to a polytype specific surface morphology [7][8][9]. In ultrahigh vacuum (UHV) experiments using molecular beam epitaxy (MBE) it was realized that such a growth mode is stabilized under silicon rich conditions when a ͑333͒ periodicity develops [10].…”

“…The ͑333͒ phase was prepared by annealing to 800 ± C under exposure to Si for 30 min. In contrast to hexagonal polytypes, on a cubic sample only one type of stacking sequence can be present at the surface [7,8]. Thus, the complication of stacking and domain mixtures is eliminated from the structure analyses.…”

SiC SURFACE RECONSTRUCTION: RELEVANCY OF ATOMIC STRUCTURE FOR GROWTH TECHNOLOGY

“…LEED structure analyses of several such samples of different polytypes and polarity indeed determined the surface geometry to consist of unreconstructed SiC bilayers, however, covered by a submonolayer amount of oxygen or hydrogen statistically adsorbed on top of the topmost atoms of the bilayer. 15,[22][23][24][25][26] An improvement of this situation can be achieved by a hydrogen etching procedure similar to a typical preparation step used before epitaxial SiC growth experiments. 27,28 When the sample is annealed in a quartz tube (e.g.…”

Polarity, Morphology and Reactivity of Epitaxial GaN Films on Al2O3(0001)

“…In fact, using this technique it is even possible to determine the relative ratio of areas of different surface stacking sequences possible due to the crystal structure of SiC [16], which could also be applied to the question of a possible presence of inversion domains and their corresponding surface area. Similar to the case of SiC [17,18], a set of fingerprints could be established allowing a quick assessment of sample polarity or possible mixtures of different orientations as shown in Fig. 3 by the results of a theoretical calculation of the spot intensities for bulk truncated models of the two surface orientations, i.e.…”