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arXiv 0904.4335cond-mat.mtrl-sci
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金属薄膜在逾渗阈值附近的介电特性

Dielectric properties of ultrathin metal films around the percolation threshold

Martin Hövel, Martin Alws, Bruno Gompf, Martin Dressel

摘要:

我们报告的光学反射测量薄Au膜的渗透阈值(膜厚3至10纳米)和周围的一个非常广泛的光谱范围从500至35000 cm-1(0.3 - 20 *10-6米)。结合椭圆偏振光谱和傅里叶变换红外光谱,薄膜的介电性能可以描述在整个频率范围内的Kramers-Kronig一致的有效介电函数。薄膜的光学电导率主要由两个贡献:在低频率范围内的渗透阈值和在近红外区域的等离子体激元,随着薄膜厚度的增加,频率向下移动的德鲁德组件开始。这两种成分的相互作用导致在红外区域中的介电异常,在绝缘体到金属的过渡处具有最大的介电常数。

英文摘要:

We report on optical reflection measurements of thin Au films at and around the percolation threshold (film thickness 3 to 10 nm) in an extremely broad spectral range from 500 to 35000 cm-1 (0.3 - 20 *10-6 m). Combining spectroscopic ellipsometry and Fourier-transform infrared spectroscopy, the dielectric properties of the films can be described over the whole frequency range by Kramers-Kronig consistent effective dielectric functions. The optical conductivity of the films is dominated by two contributions: by a Drude-component starting at the percolation threshold in the low frequency range and a plasmon in the near-infrared region, which shifts down in frequency with increasing film thickness. The interplay of both components leads to a dielectric anomaly in the infrared region with a maximum of the dielectric constant at the insulator-to-metal transition.

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