Major technological breakthroughs are often driven by advancements in materials research, and optics is no different. Over the last few years, near-zero-index (NZI) materials have triggered significant interest owing to their exceptional tunability of optical properties and enhanced light-matter interaction, leading to several demonstrations of compact, energy-efficient, and dynamic nanophotonic devices. Many of these devices have relied on transparent conducting oxides (TCOs) as a dynamic layer, as these materials exhibit a near-zero-index at telecommunication wavelengths. Among a wide range of techniques employed for the deposition of TCOs, atomic layer deposition (ALD) offers advantages such as conformality, scalability, and low substrate temperature. However, the ALD process often results in films with poor optical quality, due to low doping efficiencies at high (>1020cm−3) doping levels. In this work, we demonstrate a modified ALD process to deposit TCOs, taking Al:ZnO as an example, which results in an increase in doping efficiency from 13% to 54%. Moving away from surface saturation for the dopant (aluminum) precursor, the modified ALD process results in a more uniform distribution of dopants (Al) throughout the film, yielding highly conductive (2.8×10−4 Ω-cm) AZO films with crossover wavelengths as low as 1320nm and 1370nm on sapphire and silicon substrates, respectively.

中文翻译：

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Al:ZnO 作为近零折射率光子学的平台：提高原子层沉积的掺杂效率

重大技术突破通常是由材料研究的进步推动的，光学也不例外。在过去的几年中，近零指数 (NZI) 材料由于其光学特性的出色可调性和增强的光-物质相互作用而引起了极大的兴趣，从而导致了紧凑、节能和动态纳米光子器件的多次演示。许多这些设备依赖透明导电氧化物 (TCO) 作为动态层，因为这些材料在电信波长下表现出接近零的指数。在用于沉积 TCO 的各种技术中，原子层沉积 (ALD) 具有保形性、可扩展性和低基板温度等优点。然而，ALD 工艺通常会导致薄膜光学质量不佳，由于在高 (>1020cm−3) 掺杂水平下的低掺杂效率。在这项工作中，我们展示了一种改进的 ALD 工艺来沉积 TCO，以 Al:ZnO 为例，这导致掺杂效率从 13% 增加到 54%。远离掺杂剂（铝）前驱体的表面饱和，改进的 ALD 工艺导致掺杂剂（Al）在整个薄膜中分布更均匀，产生具有交叉波长的高导电性（2.8×10-4 Ω-cm）偶氮薄膜在蓝宝石和硅衬底上分别低至 1320nm 和 1370nm。