Shah Deesha, Yang Morris, Kudyshev Zhaxylyk, Xu Xiaohui, Shalaev Vladimir M, Bondarev Igor V, Boltasseva Alexandra
School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States.
Math & Physics Department, North Carolina Central University, Durham, North Carolina 27707, United States.
Nano Lett. 2022 Jun 22;22(12):4622-4629. doi: 10.1021/acs.nanolett.1c04692. Epub 2022 May 31.
Plasmonic transdimensional materials (TDMs), which are atomically thin metals of precisely controlled thickness, are expected to exhibit large tailorability and dynamic tunability of their optical response as well as strong light confinement and nonlocal effects. Using spectroscopic ellipsometry, we characterize the complex permittivity of ultrathin films of passivated plasmonic titanium nitride with thicknesses ranging from 1 to 10 nm. By measuring passivated TiN, we experimentally distinguish between the contributions of an oxide layer and thickness to the optical properties. A decrease in the Drude plasma frequency and increase in the damping in thinner films is observed due to spatial confinement. We explain the experimental trends using a nonlocal Drude dielectric response theory based on the Keldysh-Rytova (KR) potential that predicts the thickness-dependent optical properties caused by electron confinement in plasmonic TDMs. Our experimental findings are consistent with the KR model and demonstrate quantum-confinement-induced optical properties in plasmonic transdimensional TiN.
等离激元跨维材料（TDMs）是厚度精确可控的原子级薄金属，有望展现出其光学响应的高度可剪裁性和动态可调性，以及强光限制和非局域效应。我们使用光谱椭偏仪对厚度在1至10纳米范围内的钝化等离激元氮化钛超薄膜的复介电常数进行了表征。通过测量钝化的TiN，我们通过实验区分了氧化层和厚度对光学性质的贡献。由于空间限制，在较薄的薄膜中观察到德鲁德等离子体频率降低和阻尼增加。我们使用基于凯尔迪什 - 里托娃（KR）势的非局域德鲁德介电响应理论来解释实验趋势，该理论预测了等离激元TDMs中电子限制引起的厚度依赖光学性质。我们的实验结果与KR模型一致，并证明了等离激元跨维TiN中量子限制诱导的光学性质。
