arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2104.06545cond-mat.mtrl-sciphysics.comp-phphysics.optics
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贵金属奇异相的表面等离子体激元特性

Surface-plasmon properties of noble metals with exotic phases

Okan K. Orhan, Mauricio Ponga

摘要:

贵金属纳米颗粒由于其高度填充的等离子体激元代而成为等离子体激元应用的工业标准。尽管它们具有显著的等离子体性能,但它们在等离子体应用中的广泛使用通常由于对可用激光源的限制和在这些材料中保持机械强度所需的相对低的操作温度而受到阻碍。最近的实验工作,其中外来的六方密堆积(HCP)相已被确定在金(Au),银(Ag)和铜(Cu)的动机,我们提出了在这些材料中使用高精度的第一原理模拟的两个HCP多型体的等离子体性能。由于与面心立方(FCC)相相比吉布斯自由能差单调减小,孤立的HCP相通常在高温下达到热稳定性和机械稳定性。我们发现,这些多型体中的几个更难,并产生大量的等离子体激元在较低的能量与可比的寿命比他们传统的FCC同行。它还导致在嵌入到介电基质上的完美球形HCP相纳米颗粒中的局部表面等离子体共振(LSPR),其能量大大低于FCC对应物,寿命相当。LSPR峰的位置和寿命可以通过控制操作温度、基质的介电常数和晶粒尺寸来调节。我们的工作表明,贵金属纳米粒子可以定制开发异国情调的HCP相,以获得新的等离子体特性。

英文摘要:

Noble-metal nanoparticles have been the industry standard for plasmonic applications due to their highly populated plasmon generations. Despite their remarkable plasmonic performance, their widespread use in plasmonic applications is commonly hindered due to limitations on the available laser sources and relatively low operating temperatures needed to retain mechanical strength in these materials. Motivated by recent experimental works, in which exotic hexagonal-closed-packed (HCP) phases have been identified in gold (Au), silver (Ag) and copper (Cu), we present the plasmonic performance of two HCP polytypes in these materials using high-accuracy first-principles simulations. The isolated HCP phases commonly reach thermal and mechanical stability at high temperatures due to monotonically decreasing Gibbs free energy differences compared to the face-centered cubic (FCC) phases. We find that several of these polytypes are harder and produce bulk plasmons at lower energies with comparable lifetimes than their conventional FCC counterparts. It also leads to the localized surface-plasmon resonance (LSPR) in perfectly spherical HCP-phased nanoparticles, embedded onto dielectric matrices, at substantially lower energies with comparable lifetimes to their FCC counterparts. LSPR peak locations and lifetimes can be tuned by controlling the operational temperature, the dielectric permittivity of hosting matrix and the grain size. Our work suggests that noble-metal nanoparticles can be tailored to develop exotic HCP phases to obtain novel plasmonic properties.

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