{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T14:19:18Z","timestamp":1778595558010,"version":"3.51.4"},"reference-count":36,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2022,3,14]],"date-time":"2022-03-14T00:00:00Z","timestamp":1647216000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key R&amp;D Program of China","doi-asserted-by":"publisher","award":["2021YFA0716400"],"award-info":[{"award-number":["2021YFA0716400"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Guangdong Basic and Application Basic Research Foundation of Guangdong Province","award":["2021B1515120022"],"award-info":[{"award-number":["2021B1515120022"]}]},{"name":"Guangdong Basic and Application Basic Research Foundation of Guangdong Province","award":["2020A1515110891"],"award-info":[{"award-number":["2020A1515110891"]}]},{"name":"Guangdong Basic and Application Basic Research Foundation of Guangdong Province","award":["2019B1515120091"],"award-info":[{"award-number":["2019B1515120091"]}]},{"name":"Guangdong Basic and Application Basic Research Foundation of Guangdong Province","award":["2019B1515120081"],"award-info":[{"award-number":["2019B1515120081"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>In the present work, a single-crystalline epitaxial nonpolar a-plane AlN film with in-plane two-folder symmetries was successfully achieved on an r-plane sapphire substrate, by combining physical vapor deposition and a high-temperature annealing technique. Moreover, by varying the AlN thickness, the evolution of crystalline quality and structure were systematically investigated using X-ray diffraction, Raman spectroscopy, and atomic force microscopy. The crystalline quality was much improved by the annealing treatment. Most importantly, when the thickness of AlN was increased up to 1000 nm, the AlN lattice was found to endure strong distortion along the out-of-plane direction, and the lattice showed an obvious expansion. The change of the surface morphology induced by high-temperature annealing was also tracked, and the morphology displayed structural anisotropy along the [11\u00af00] direction. Our results act as a crucial platform to better understand and employ the nonpolar AlN template; in particular, it is of importance for subsequent device fabrication.<\/jats:p>","DOI":"10.3390\/sym14030573","type":"journal-article","created":{"date-parts":[[2022,3,15]],"date-time":"2022-03-15T02:56:20Z","timestamp":1647312980000},"page":"573","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["The In-Plane-Two-Folders Symmetric a-Plane AlN Epitaxy on r-Plane Sapphire Substrate"],"prefix":"10.3390","volume":"14","author":[{"given":"Fabi","family":"Zhang","sequence":"first","affiliation":[{"name":"Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin University of Electronic Technology, Guilin 541004, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lijie","family":"Huang","sequence":"additional","affiliation":[{"name":"Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin University of Electronic Technology, Guilin 541004, China"},{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jin","family":"Zhang","sequence":"additional","affiliation":[{"name":"Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin University of Electronic Technology, Guilin 541004, China"},{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhiwen","family":"Liang","sequence":"additional","affiliation":[{"name":"Dongguan Institute of Optoelectronics, Peking University, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0124-6315","authenticated-orcid":false,"given":"Chenhui","family":"Zhang","sequence":"additional","affiliation":[{"name":"Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shangfeng","family":"Liu","sequence":"additional","affiliation":[{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"},{"name":"State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wei","family":"Luo","sequence":"additional","affiliation":[{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Junjie","family":"Kang","sequence":"additional","affiliation":[{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jiakang","family":"Cao","sequence":"additional","affiliation":[{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tai","family":"Li","sequence":"additional","affiliation":[{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"},{"name":"State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7129-1974","authenticated-orcid":false,"given":"Qi","family":"Wang","sequence":"additional","affiliation":[{"name":"Dongguan Institute of Optoelectronics, Peking University, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ye","family":"Yuan","sequence":"additional","affiliation":[{"name":"Songshan Lake Materials Laboratory, Dongguan 523808, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,3,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"884","DOI":"10.1038\/nphoton.2014.291","article-title":"The birth of the blue LED","volume":"8","author":"Nanishi","year":"2014","journal-title":"Nat. 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