Refractive Index Tuning of All-Inorganic TiO 2 Nanocrystal-Based Films and High Aspect Ratio Nanostructures Using Atomic Layer Deposition: Implications for High-Throughput Fabrication of Metalenses
Refractive Index Tuning of All-Inorganic TiO 2 Nanocrystal-Based Films and High Aspect Ratio Nanostructures Using Atomic Layer Deposition: Implications for High-Throughput Fabrication of Metalenses
复制标题
使用原子层沉积对全无机 TiO 2 纳米晶体基薄膜和高纵横比纳米结构进行折射率调节：对超透镜高通量制造的影响
DOI：
10.1021/acsanm.2c04982
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发表时间：
2023
影响因子：
5.9
通讯作者：
Watkins, James J.
中科院分区：
文献类型：
--
作者：
Jung, Dae Eon;Howell, Irene R.;Einck, Vincent J.;Arisoy, Feyza Dundar;Verrastro, Lucas D.;McClung, Andrew;Arbabi, Amir;Watkins, James J.
高折射率 (RI) 组件和纳米结构对于紧凑型光学、波导、光子学和超材料具有极大的吸引力。在此，我们证明原子层沉积 (ALD) 可以用作一个简短的后加工步骤，与单步直接纳米压印光刻 (NIL) 相结合，可显着提高纳米晶体 (NC) 基薄膜和图案化纳米结构的 RI。 TiO2NC 基薄膜的初始 RI 在 543 nm 处为 1.95，然后可以通过后煅烧将其增加至 2.00，并通过 TiO2ALD 进一步增加至 2.15。十五个 ALD 循环足以实现 RI 的快速增加，并且可以通过相应调整 ALD 循环数来调整任何中间 RI 值。 TiO2NC 之间的纳米级间隙允许 ALD 前驱体均匀扩散，从而产生更致密的结构和 RI 增加。制造了 4 毫米大小的超透镜阵列，以演示 RI 调谐对光学器件性能的影响。压印超透镜（最小尺寸约 80 nm，最高纵横比约 8）的平均聚焦效率为 61%，但包括煅烧和 ALD 在内的后处理将平均效率显着提高至 67%，而性能最佳的透镜则高达 75%。该方法结合了快速、可扩展且多功能的溶剂辅助 NIL 方法来图案化光学纳米结构，并通过短的图案化后沉积和致密化步骤来显着增强光学性能。
High refractive index (RI) components and nanostructures are of great interest for compact optics, waveguides, photonics, and metamaterials. Herein, we demonstrate that atomic layer deposition (ALD) can be used as a short postfabrication step to dramatically increase the RI of nanocrystal (NC)-based films and patterned nanostructures in conjunction with a single-step, direct nanoimprint lithography (NIL). The initial RI of TiO2NC-based films wasn= 1.95 at 543 nm which can then be increased to 2.00 by post-calcination and further up to 2.15 by TiO2ALD. Fifteen cycles of ALD were sufficient to achieve this rapid increase of RI, and any intermediate RI value can be tuned by adjusting the number of ALD cycles accordingly. Nanoscale interstitial gaps between TiO2NCs allowed a uniform diffusion of ALD precursors, resulting in a much denser structure and the RI increase. An array of 4 mm-sized metalenses were fabricated to demonstrate the effects of the RI tuning on the performance of optical devices. The focusing efficiencies of the as-imprinted metalenses (smallest dimension ∼ 80 nm, highest aspect ratio ∼ 8) were 61% on average, but the post-treatments including calcination and ALD significantly increased the average efficiency to 67% and up to 75% for the best-performing lens. This approach combines the fast, scalable, and versatile solvent-assisted NIL method to pattern optical nanostructures with a short post-patterning deposition and densification step that significantly enhances optical performance.