The Role of Optical Phonon Confinement in the Infrared Dielectric Response of III–V Superlattices
The Role of Optical Phonon Confinement in the Infrared Dielectric Response of III–V Superlattices
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光学声子约束在 III-V 族超晶格红外介电响应中的作用
DOI：
10.1002/adma.202305106
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发表时间：
2023
影响因子：
29.4
通讯作者：
Beechem, Thomas
中科院分区：
文献类型：
--
作者：
Matson, Joseph R.;Alam, Md Nazmul;Varnavides, Georgios;Sohr, Patrick;Knight, Sean;Darakchieva, Vanya;Stokey, Megan;Schubert, Mathias;Said, Ayman;Beechem, Thomas
极性材料是红外（IR）纳米光子应用的关键材料，因为它们能够承载声子极化激元，从而实现低损耗，亚衍射控制光。声子-极化激元的性质受到光学声子特性的限制，对于大多数“体”材料，光学声子的特性名义上是固定的。由交替的原子级薄材料组成的超晶格通过成分的变化、光学声子限制和新模式的出现提供对晶体各向异性的控制。特别是，超晶格中的改性光学声子提供了所谓的晶体混合物的潜力，其IR特性不能被描述为体成分的简单混合物。然而，迄今为止，研究主要集中在确定新的或修改的光学声子模式的存在，而不是评估其对IR响应的影响。本研究的重点是评估限制光学声子模式的混合红外超晶格的GaSb和AlSb的介电函数的影响。使用第一原理理论、拉曼、傅里叶变换红外光谱和椭圆偏振光谱的组合，发现混合介电函数跟踪光学声子的限制，导致光学声子光谱位移高达20 cm−1。这些结果为红外光学材料的设计提供了一条新的途径。
Polar dielectrics are key materials of interest for infrared (IR) nanophotonic applications due to their ability to host phonon‐polaritons that allow for low‐loss, subdiffractional control of light. The properties of phonon‐polaritons are limited by the characteristics of optical phonons, which are nominally fixed for most “bulk” materials. Superlattices composed of alternating atomically thin materials offer control over crystal anisotropy through changes in composition, optical phonon confinement, and the emergence of new modes. In particular, the modified optical phonons in superlattices offer the potential for so‐called crystalline hybrids whose IR properties cannot be described as a simple mixture of the bulk constituents. To date, however, studies have primarily focused on identifying the presence of new or modified optical phonon modes rather than assessing their impact on the IR response. This study focuses on assessing the impact of confined optical phonon modes on the hybrid IR dielectric function in superlattices of GaSb and AlSb. Using a combination of first principles theory, Raman, FTIR, and spectroscopic ellipsometry, the hybrid dielectric function is found to track the confinement of optical phonons, leading to optical phonon spectral shifts of up to 20 cm−1. These results provide an alternative pathway toward designer IR optical materials.