Surface morphology and composition of c-, a- and m-sapphire surfaces in O2 and H2 environments |
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Authors: | Stefano Curiotto Dominique Chatain |
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Institution: | aCNRS, Aix-Marseille University, CINAM-UPR3118, Campus de Luminy, Case 913, 13288 Marseille, France |
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Abstract: | This paper reports that monitoring the composition of the c(0 0 0 1), a(11–20) and m(10–10) sapphire surfaces is essential for a proper interpretation of the surface morphologies obtained after annealing at 1253 and 1473 K in Ar H2 or Ar O2 atmospheres. Our experimental investigations, which have used Auger electron spectroscopy (AES) and atomic force microscopy (AFM) on the surfaces of 99.99% pure sapphire wafers, have led to the following original conclusions: (i) Calcium segregates at the c-surface of sapphire both under Ar O2 and Ar H2. (ii) Potassium adsorption enhances the kinetics of step-bunching on the c-surface under Ar O2. (iii) The step edges on the a-surface may develop a comb-like morphology made of parallel strips along the 10–10] direction. (iv) At 1253 K, clean m-surfaces may be stable. (v) Under Ar H2, alumina surface diffusion is much slower than under Ar O2 for all surface orientations, the surface concentration of impurities is low, and the Al–O ratio of the AES signals at the surface is significantly larger. |
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Keywords: | Aluminium oxide Hydrogen Oxygen Surface topography Surface composition |
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