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Crystallographic and Topographical Evolutions of Cylinder Patterned Sapphire Substrate Etched with Sulfuric Acid and Phosphoric Acid Mixture: An SEM and AFM Study

Abstract

Crystallographic and topographical evolutions of cylinder patterned sapphire substrate (PSS) under an ordinary wet etching condition (H2SO4:H3PO4 = 5:1 at volume ratio, 230°C) were systematically studied using complementary SEM and AFM characterizations. The strongly time-dependent crystallographic and topographical evolutions of cylinder protrusions were revealed. Cylinders changed to triangular frustums with co-existed top c-plane, to triangular pyramids with multiple high Miller index planes, then to hexagonal pyramids, and finally to triangular pyramids with a single family of planes. The Miller indices of five major crystallographic planes were determined: CY2 {1 -1 0 15}, CY3 {1 -1 0 6}, CY4b {-1 1 0 5}, CY5 {4 -5 1 38}, and CY6 {1 -1 0 12} with the first three being reported for the first time to our best knowledge. The etching rates of crystallographic planes follow the order: CY3 > CY5 > CY6 > CY2 > c plane. It was clearly demonstrated that cylinder protrusions, featuring steep sidewall, circular symmetry, and top c-plane, are suitable for studying full spectrum of crystallographic and topographical evolution characteristics of PSS as well as for fabricating optimized PSS with specific slant angle for enhanced performance of light emitting diodes in the future.

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Publication details

The article was received on 18 Aug 2017, accepted on 28 Sep 2017 and first published on 29 Sep 2017


Article type: Paper
DOI: 10.1039/C7CE01506B
Citation: CrystEngComm, 2017, Accepted Manuscript
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    Crystallographic and Topographical Evolutions of Cylinder Patterned Sapphire Substrate Etched with Sulfuric Acid and Phosphoric Acid Mixture: An SEM and AFM Study

    J. Shen, D. Zhang, Y. Wang and Y. Gan, CrystEngComm, 2017, Accepted Manuscript , DOI: 10.1039/C7CE01506B

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