石墨烯具有優異導電性、熱傳導性與機械化學穩定性，近幾年已被廣泛運用於發光二極體中改善元件性能。如:石墨烯界面層可使用來降低元件內部插排缺陷密度，然而，石墨烯光穿透率隨其層數增加而下降，導入石墨烯將使LED發光亮度降低。本研究針對此問題提出網狀石墨烯界面層減少石墨烯的吸光問題。具體作法為使用陽極氧化鋁遮罩製作凹槽型奈米圖案藍寶石基板，隨後沉積金屬銅於表面，透過低壓化學氣相沉積系統將石墨烯成長在此凹槽型奈米圖案基板上，由於凹槽內無法成長出石墨烯，僅無圖案之C面處可成長出網狀石墨烯界面層。此外，藉由調整電解液濃度、電場強度、陽極偏壓、陽極氧化鋁反應時間以及擴孔時間等參數，可製備出具不同孔洞圖案面積佔比之陽極氧化鋁遮罩。並以乾蝕刻將孔洞圖案轉移至基板，本研究成功製備出三種孔洞面積佔比率24 %、50 %、76 %之凹槽奈米圖案藍寶石基板，進而製備出高穿透率之網狀石墨烯界面層。值得一提，由拉曼光譜分析，孔洞佔比24 %，密度1.7 × 109 cm-2、孔洞直徑134.4 nm、穿透率78.2 %之網狀石墨烯界面層，D band與G band 強度比為0.4，2D band 半高寬為72.0 cm-1未來有潛力運用於藍寶石基板上，改善元件之性能。

Graphene has many excellent properties, such as high electrical conductivity, high thermal conductivity, mechanical toughness, and chemical inertness. In recent years, graphene has been widely used in InGaN-based light-emitting diodes (InGaN LEDs) to improve device performance. For example, the graphene interface layer was used to reduce the threading dislocation density of InGaN LEDs. However, the transmittance of graphene decreases with increasing the layer number. Thus, it can be predicted that embedding graphene inside InGaN LEDs will decrease the brightness. To address this issue, a concept of mesh structure is proposed for increasing the transmittance of graphene interlayer.
The fabrication processes of mesh graphene are including an anodized aluminum oxide (AAO) mask used to obtain a concave nanopattern sapphire substrate (CNPSS), deposit metal copper on the CNPSS surface, and grow graphene on the CNPSS using a low-pressure chemical vapor deposition system. The experimental results indicated that the dewetting phenomenon of the copper thin film at the high epitaxy temperature lets graphene can’t grow inside the concave pattern region of CNPSS. Thus, graphene only grows on the unpatterned region of CNPSS. In addition, the various pattern occupancy ratios of AAO masks can be obtained by changing experimental parameters such as electrolyte concentration, electric field, anodic voltage, anodized time, and pore-widening time. Using a dry etching process, various pattern occupancy ratios of CNPSS can be prepared. In this study, three various pattern occupancy rations (24 %, 50 %, and 76 %) of CNPSS are prepared for achieving high transmittance mesh graphene interlayer. It is worth mentioning that the transmittance of 78.2 % of mesh graphene interlayer on the pattern occupancy ratio of 24% CNPSS (i.e. pattern density of 1.7 × 109 cm-2, pattern diameter of 134.4 nm) is obtained. The Raman spectrum indicated the peak intensity ratio of the D band and G band is 0.4, and the FWHM of the 2D band peak is 72.0 cm-1. This study presents mesh graphene interlayer on CNPSS as a promising substrate for further InGaN LEDs epitaxy.

1.https://www.yolegroup.com/,
2.https://navitassemi.com/,
3.Ki-Sik Im, Jong-Bong Ha, Ki-Won Kim, Jong-Sub Lee, Dong-Seok Kim, Sung-Ho Hahm, and Jung-Hee Lee, Normally off GaN MOSFET based on AlGaN/GaN heterostructure with extremely high 2DEG density grown on silicon substrate, IEEE Electron Device Letters.(2010). 31, p.192.
4.Lung-Hsing Hsu, Yung-Yu Lai, Po-Tsung Tu, Catherine Langpoklakpam, Ya-Ting Chang, Yu-Wen Huang, Wen-Chung Lee, An-Jye Tzou, Yuh-Jen Cheng, and Chun-Hsiung Lin, Development of GaN HEMTs fabricated on silicon, silicon-on-insulator, and engineered substrates and the heterogeneous integration, Micromachines.(2021). 12, p.1159.
5.Weili Liu and Alexander A Balandin, Thermal conduction in Al x Ga 1− x N alloys and thin films, Journal of Applied Physics.(2005). 97, p.073710.
6.Scott W Finefrock, Yan Wang, John B Ferguson, James V Ward, Haiyu Fang, Jonathan E Pfluger, Douglas S Dudis, Xiulin Ruan, and Yue Wu, Measurement of thermal conductivity of pbte nanocrystal coated glass fibers by the 3ω method, Nano Letters.(2013). 13, p.5006.
7.Wanjun Cao, Jeffrey M Biser, Yik-Khoon Ee, Xiao-Hang Li, Nelson Tansu, Helen M Chan, and Richard P Vinci, Dislocation structure of GaN films grown on planar and nano-patterned sapphire, Journal of Applied Physics.(2011). 110, p.053505.
8.Hideki Masuda and Kenji Fukuda, Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina, science.(1995). 268, p.1466.
9.YC Sui, BZ Cui, L Martınez, R Perez, and David J Sellmyer, Pore structure, barrier layer topography and matrix alumina structure of porous anodic alumina film, Thin Solid Films.(2002). 406, p.64.
10.Ming-lun Hsieh, National Central University, 2006.
11.VP Parkhutik and VI Shershulsky, Theoretical modelling of porous oxide growth on aluminium, Journal of Physics D: Applied Physics.(1992). 25, p.1258.
12.A Belwalkar, E Grasing, W Van Geertruyden, Z Huang, and WZ Misiolek, Effect of processing parameters on pore structure and thickness of anodic aluminum oxide (AAO) tubular membranes, Journal of membrane science.(2008). 319, p.192.
13.Feiyue Li, Lan Zhang, and Robert M Metzger, On the growth of highly ordered pores in anodized aluminum oxide, Chemistry of materials.(1998). 10, p.2470.
14.MK Kushwaha, A comparative Study of Different Electrolytes for Obtaining Thick and Well-ordered nano-porous Anodic Aluminium Oxide (AAO) Films, Procedia Materials Science.(2014). 5, p.1266.
15.Woo Lee and Sang-Joon Park, Porous anodic aluminum oxide: anodization and templated synthesis of functional nanostructures, Chemical reviews.(2014). 114, p.7487.
16.Nando Kaminski and Oliver Hilt, SiC and GaN devices–wide bandgap is not all the same, IET Circuits, Devices & Systems.(2014). 8, p.227.
17.Hui-Youn Shin, SK Kwon, YI Chang, MJ Cho, and KH Park, Reducing dislocation density in GaN films using a cone-shaped patterned sapphire substrate, Journal of Crystal Growth.(2009). 311, p.4167.
18.Wen-Cheng Ke, Fang-Wei Lee, Chih-Yung Chiang, Zhong-Yi Liang, Wei-Kuo Chen, and Tae-Yeon Seong, InGaN-based light-emitting diodes grown on a micro/nanoscale hybrid patterned sapphire substrate, ACS Applied Materials & Interfaces.(2016). 8, p.34520.
19.Gai Zhang, Le Chang, Hua Shao, Chunshuang Chu, Chao Fan, Yandi Zhang, Yonghui Zhang, and Zi-Hui Zhang, Enhanced optical output of GaN-based near-ultraviolet light-emitting diodes using an ultra-thin air cavity nanopatterned sapphire substrate, CrystEngComm.(2022). 24, p.3020.
20.John C Hulteen and Richard P Van Duyne, Nanosphere lithography: A materials general fabrication process for periodic particle array surfaces, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films.(1995). 13, p.1553.
21.Jian-Jhong Chen, Yan-Kuin Su, Chuing-Liang Lin, Shi-Ming Chen, Wen-Liang Li, and Chien-Chih Kao, Enhanced output power of GaN-based LEDs with nano-patterned sapphire substrates, IEEE Photonics Technology Letters.(2008). 20, p.1193.
22.Ya-Ju Lee, Tien-Chang Lu, Hao-Chung Kuo, and Shing-Chung Wang, High brightness GaN-based light-emitting diodes, Journal of Display Technology.(2007). 3, p.118.
23.Stephen Y Chou, Peter R Krauss, Wei Zhang, Lingjie Guo, and Lei Zhuang, Sub-10 nm imprint lithography and applications, Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena.(1997). 15, p.2897.
24.Yi-Ta Hsieh and Yung-Chun Lee, Direct metal contact printing lithography for patterning sub-micrometer surface structures on a sapphire substrate, Journal of Micromechanics and Microengineering.(2010). 21, p.015001.
25.DS Wuu, WK Wang, KS Wen, SC Huang, SH Lin, Ray-Hua Horng, YS Yu, and MH Pan, Fabrication of pyramidal patterned sapphire substrates for high-efficiency InGaN-based light emitting diodes, Journal of The Electrochemical Society.(2006). 153, p.G765.
26.Nan Xie, Fujun Xu, Na Zhang, Jing Lang, Jiaming Wang, Mingxing Wang, Yuanhao Sun, Baiyin Liu, Weikun Ge, and Zhixin Qin, Period size effect induced crystalline quality improvement of AlN on a nano-patterned sapphire substrate, Japanese Journal of Applied Physics.(2019). 58, p.100912.
27.Fang-Wei Lee, Wen-Cheng Ke, Chun-Hong Cheng, Bo-Wei Liao, and Wei-Kuo Chen, Influence of different aspect ratios on the structural and electrical properties of GaN thin films grown on nanoscale-patterned sapphire substrates, Applied Surface Science.(2016). 375, p.223.
28.Kostya S Novoselov, Andre K Geim, Sergei V Morozov, De-eng Jiang, Yanshui Zhang, Sergey V Dubonos, Irina V Grigorieva, and Alexandr A Firsov, Electric field effect in atomically thin carbon films, science.(2004). 306, p.666.
29.MI Katsnelson and KS Novoselov, Graphene: New bridge between condensed matter physics and quantum electrodynamics, Solid State Communications.(2007). 143, p.3.
30.Changgu Lee, Xiaoding Wei, Jeffrey W Kysar, and James Hone, Measurement of the elastic properties and intrinsic strength of monolayer graphene, science.(2008). 321, p.385.
31.Alexander A Balandin, Thermal properties of graphene and nanostructured carbon materials, Nature materials.(2011). 10, p.569.
32.Wanyoung Jang, Zhen Chen, Wenzhong Bao, Chun Ning Lau, and Chris Dames, Thickness-dependent thermal conductivity of encased graphene and ultrathin graphite, Nano letters.(2010). 10, p.3909.
33.Xu Du, Ivan Skachko, Anthony Barker, and Eva Y Andrei, Approaching ballistic transport in suspended graphene, Nature nanotechnology.(2008). 3, p.491.
34.Guoqing Xin, Tiankai Yao, Hongtao Sun, Spencer Michael Scott, Dali Shao, Gongkai Wang, and Jie Lian, Highly thermally conductive and mechanically strong graphene fibers, Science.(2015). 349, p.1083.
35.Yu Lin Zhong, Zhiming Tian, George P Simon, and Dan Li, Scalable production of graphene via wet chemistry: progress and challenges, Materials Today.(2015). 18, p.73.
36.Peter Blake, Paul D Brimicombe, Rahul R Nair, Tim J Booth, Da Jiang, Fred Schedin, Leonid A Ponomarenko, Sergey V Morozov, Helen F Gleeson, and Ernie W Hill, Graphene-based liquid crystal device, Nano letters.(2008). 8, p.1704.
37.Konstantin V Emtsev, Aaron Bostwick, Karsten Horn, Johannes Jobst, Gary L Kellogg, Lothar Ley, Jessica L McChesney, Taisuke Ohta, Sergey A Reshanov, and Jonas Röhrl, Towards wafer-size graphene layers by atmospheric pressure graphitization of silicon carbide, Nature materials.(2009). 8, p.203.
38.Xin Li, Jiaguo Yu, S Wageh, Ahmed A Al‐Ghamdi, and Jun Xie, Graphene in photocatalysis: a review, Small.(2016). 12, p.6640.
39.Velram Balaji Mohan, Kin-tak Lau, David Hui, and Debes Bhattacharyya, Graphene-based materials and their composites: A review on production, applications and product limitations, Composites Part B: Engineering.(2018). 142, p.200.
40.Yue Qi, Yunyu Wang, Zhenqian Pang, Zhipeng Dou, Tongbo Wei, Peng Gao, Shishu Zhang, Xiaozhi Xu, Zhenghua Chang, and Bing Deng, Fast growth of strain-free AlN on graphene-buffered sapphire, Journal of the American Chemical Society.(2018). 140, p.11935.
41.M Kadleıková, J Breza, and M Veselý, Raman spectra of synthetic sapphire, Microelectronics journal.(2001). 32, p.955.
42.Jia-bin Wang, Zhuang Ren, Ying Hou, Xiao-li Yan, Pei-zhi Liu, Hua Zhang, Hai-xia Zhang, and Jun-jie Guo, A review of graphene synthesisatlow temperatures by CVD methods, New Carbon Materials.(2020). 35, p.193.
43.Alfonso Reina, Xiaoting Jia, John Ho, Daniel Nezich, Hyungbin Son, Vladimir Bulovic, Mildred S Dresselhaus, and Jing Kong, Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition, Nano letters.(2009). 9, p.30.
44.HoKwon Kim, Cecilia Mattevi, M Reyes Calvo, Jenny C Oberg, Luca Artiglia, Stefano Agnoli, Cyrus F Hirjibehedin, Manish Chhowalla, and Eduardo Saiz, Activation energy paths for graphene nucleation and growth on Cu, ACS nano.(2012). 6, p.3614.
45.A Varykhalov and O Rader, Graphene grown on Co (0001) films and islands: Electronic structure and its precise magnetization dependence, Physical Review B.(2009). 80, p.035437.
46.Nikolay A Vinogradov, AA Zakharov, Vancho Kocevski, Jan Rusz, KA Simonov, Olle Eriksson, Anders Mikkelsen, Edvin Lundgren, AS Vinogradov, and Nils Mårtensson, Formation and structure of graphene waves on Fe (110), Physical review letters.(2012). 109, p.026101.
47.Johann Coraux, Alpha T N ‘Diaye, Carsten Busse, and Thomas Michely, Structural coherency of graphene on Ir (111), Nano letters.(2008). 8, p.565.
48.Roberto Munoz and Cristina Gómez‐Aleixandre, Review of CVD synthesis of graphene, Chemical Vapor Deposition.(2013). 19, p.297.
49.Ching-Yuan Su, Ang-Yu Lu, Chih-Yu Wu, Yi-Te Li, Keng-Ku Liu, Wenjing Zhang, Shi-Yen Lin, Zheng-Yu Juang, Yuan-Liang Zhong, and Fu-Rong Chen, Direct formation of wafer scale graphene thin layers on insulating substrates by chemical vapor deposition, Nano letters.(2011). 11, p.3612.
50.Geetanjali Deokar, Jose Avila, Ivy Razado-Colambo, J-L Codron, Christophe Boyaval, Elisabeth Galopin, M-C Asensio, and Dominique Vignaud, Towards high quality CVD graphene growth and transfer, Carbon.(2015). 89, p.82.
51.Ariel Ismach, Clara Druzgalski, Samuel Penwell, Adam Schwartzberg, Maxwell Zheng, Ali Javey, Jeffrey Bokor, and Yuegang Zhang, Direct chemical vapor deposition of graphene on dielectric surfaces, Nano letters.(2010). 10, p.1542.
52.Irene Calizo, W Bao, F Miao, CN Lau, and Alexander A Balandin, Graphene-on-sapphire and graphene-on-glass: Raman spectroscopy study, arXiv preprint arXiv:0710.2369.(2007).
53.Hoda Malekpour and Alexander A Balandin, Raman‐based technique for measuring thermal conductivity of graphene and related materials, Journal of Raman Spectroscopy.(2018). 49, p.106.
54.吴娟霞, 徐华, and 张锦, 拉曼光谱在石墨烯结构表征中的应用, 化学学报.(2014). 72, p.301.
55.Shanshan Chen, Arden L Moore, Weiwei Cai, Ji Won Suk, Jinho An, Columbia Mishra, Charles Amos, Carl W Magnuson, Junyong Kang, and Li Shi, Raman measurements of thermal transport in suspended monolayer graphene of variable sizes in vacuum and gaseous environments, ACS nano.(2011). 5, p.321.
56.Zhiqiang Tu, Zhuchen Liu, Yongfeng Li, Fan Yang, Liqiang Zhang, Zhen Zhao, Chunming Xu, Shangfei Wu, Hongwen Liu, and Haitao Yang, Controllable growth of 1–7 layers of graphene by chemical vapour deposition, Carbon.(2014). 73, p.252.
57.Yufeng Hao, Yingying Wang, Lei Wang, Zhenhua Ni, Ziqian Wang, Rui Wang, Chee Keong Koo, Zexiang Shen, and John TL Thong, Probing layer number and stacking order of few‐layer graphene by Raman spectroscopy, small.(2010). 6, p.195.
58.Leandro M Malard, Marcos Assunção Pimenta, Gene Dresselhaus, and Mildred Spiewak Dresselhaus, Raman spectroscopy in graphene, Physics reports.(2009). 473, p.51.
59.Anindya Das, Biswanath Chakraborty, and Ajay Kumar Sood, Raman spectroscopy of graphene on different substrates and influence of defects, Bulletin of Materials Science.(2008). 31, p.579.