Institute for Single Crystals

National Academy of Sciences of Ukraine

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Sapphire Substrates for Micro- and Optoelectronics


Step-terrace structure on the vicinal (0001) surface of sapphire substrates are fabricated

Sapphire is one of the most widely used of substrate material. The attractive interest in are sapphire substrates with nanostructured surface. Nanosized relief with the step-terrace structure may be formed on extremely smooth crystal surface with small deflection angles from crystallographic plane (vicinal surface) if its roughness Ra is close to distance between neighboring sublattices of crystal cell.
Schematic representation of the atomic steps on vicinal (0001) sapphire:
h ~ d x tg φ  
 h – height of steps 0.22 nm,
 d - width of steps,
φ - deflection angle.
Scheme terraces

    Step-terrace relief of sapphire substrate could be used as effective template for self-organisation metal nanoclusters (Cu, Pd, Ag, Au, Ni, Co), polymers, protein, DNA molecules. The nanostructured surface also may promote obtaining dislocation-free mono- and multilayer films, in particular, for epitaxy growth of III-V and II-VI compounds for construction of light emitting diodes and laser diodes.
    The sapphire substrates (0001) with nanostructured surface with uniform distribution of terraces and steps in width d from 38 to 2000 nm are obtained. The width of steps d increases with decreasing the angle of deflection φ geometric surface from a crystallographic plane. Height of steps h nearby 0.22нм.
AFM-images of (0001) sapphire substrate and surface profilogram (atomic force microscopy).
d=220nm, φ=4′, Ra=0.99nm
(scan 5х5 μm).
d=165nm, φ=6′, Ra=0.64nm
(scan 1x1 μm).
d=38nm, φ=60′, Ra=0.69nm
(scan 1x1 μm).
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