![]() ![]() ![]() On the one hand, this step structure affects the growth quality of the LED epitaxial layer 18, 19, 20. Several research teams have produced atomically flat surfaces through ultra-precision manufacturing and the surfaces had globally regular atomic step-and-terrace structures 13, 14, 15, 16, 17. Thus, a defect-free smooth surface is essential. For film and epitaxy, the substrate surface properties greatly affect the growing quality 2, 4, 5, 6, 12. The sapphire is often used as a substrate in the integrated circuits industry, optoelectronic industry and for many scientific applications 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps). A comparison between experimental results and idealized step models of different surface compositions has been made. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). The simulation of idealized steps was constructed theoretically on the basis of experimental results. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). ![]() In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. ![]() However, very limited attention has been paid to the step formation in manufacturing process. Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. ![]()
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