Study on mechanism of generating an ultra flat surface by MBE

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Epitaxial growth is molecular deposition along crystalline orientation of substrate. Si-Si Molecular Beam Epitaxy (MBE), one of the epitaxial growth methods, is physical thermal process. That is, Si molecules given thermal energy from heated substrate can migrate on the substrate, reach to the lower potential energy positions and be caught there. So it is expected that the potential energy of the generated surface becomes more even, hence the newly surface becomes geometrically flat and crystallographically aligned. The present study made the relation clear between the substrate orientation, the surface migration and the property of the generated surface.In the experiment, pure Si was homo-epitaxially grown up onto the same substrate temperature (800ﾟC), the number of supplied molecules and the grown time. The orientation of the Si substrate was only varied (001), (113), (111), (331) and (110), which belong to <110> crystal zone.The generated surface, which was observed by the help of … More Atomic Force Microscope (AFM) in suitable environment, was different to the substrate orientation. Each generated shape consisted of the specific crystal planes in which the density of dangling bonds was lower into the substrate. It was thought that these planes were slower deposition rate than the others because the planes were difficult to transfer the thermal energy of molecules. Then, the generated surface on (111) was the smoothest one. On the other hand, the generated surface on (331) was the roughest one.These results were clarified that the dangling bonds take the thermal energy of molecules away and the amount of this lost energy depended on the density of dangling bond. Thus, if the density of dangling bonds on the substrate orientation is the lowest, the density of the dangling bonds in the lower potential energy positions is relatively higher than another positions on the substrate and easy to lose the thermal energy of molecules. Therefore, the generated surface on this substrate could be flattened. Less