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Crystallographic and topographical evolutions of a cylinder patterned sapphire substrate etched with a sulfuric acid and phosphoric acid mixture: an SEM and AFM study

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Abstract

Crystallographic and topographical evolutions of a cylinder patterned sapphire substrate (PSS) under ordinary wet etching conditions (H2SO4 : H3PO4 = 5 : 1 volume ratio, 230 °C) were systematically studied using complementary SEM and AFM characterization techniques. The strongly time-dependent crystallographic and topographical evolutions of cylinder protrusions were revealed. Cylinders changed to triangular frustums with co-existing top c-planes, 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 with combining macron] 0 15}, CY3 {1 [1 with combining macron] 0 6}, CY4b {[1 with combining macron] 1 0 5}, CY5 {4 [5 with combining macron] 1 38}, and CY6 {1 [1 with combining macron] 0 12}, with the first three being reported for the first time to the best of our knowledge. The etching rates of the crystallographic planes follow the order: CY3 > CY5 > CY6 > CY2 > c plane. It was clearly demonstrated that cylinder protrusions, featuring steep sidewalls, circular symmetry, and top c-planes, are suitable for studying the full spectrum of crystallographic and topographical evolution characteristics of the PSS, as well as for fabricating optimized PSSs with a specific slant angle for enhancing the performance of light emitting diodes in the future.

Graphical abstract: Crystallographic and topographical evolutions of a cylinder patterned sapphire substrate etched with a sulfuric acid and phosphoric acid mixture: an SEM and AFM study

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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, Advance Article
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    Crystallographic and topographical evolutions of a cylinder patterned sapphire substrate etched with a sulfuric acid and phosphoric acid mixture: an SEM and AFM study

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

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