Hanefeld Marc, Gruszka Peter, Huth Michael
Physikalisches Institut, Goethe Universität, Frankfurt am Main, 60438, Germany.
Sci Rep. 2021 Jul 26;11(1):15163. doi: 10.1038/s41598-021-94575-w.
Nano-granular metals are materials that fall into the general class of granular electronic systems in which the interplay of electronic correlations, disorder and finite size effects can be studied. The charge transport in nano-granular metals is dominated by thermally-assisted, sequential and correlated tunneling over a temperature-dependent number of metallic grains. Here we study the frequency-dependent conductivity (AC conductivity) of nano-granular Platinum with Pt nano-grains embedded into amorphous carbon (C). We focus on the transport regime on the insulating side of the insulator metal transition reflected by a set of samples covering a range of tunnel-coupling strengths. In this transport regime polarization contributions to the AC conductivity are small and correlation effects in the transport of free charges are expected to be particularly pronounced. We find a universal behavior in the frequency dependence that can be traced back to the temperature-dependent zero-frequency conductivity (DC conductivity) of Pt/C within a simple lumped-circuit analysis. Our results are in contradistinction to previous work on nano-granular Pd/[Formula: see text] in the very weak coupling regime where polarization contributions to the AC conductivity dominated. We describe possible future applications of nano-granular metals in proximity impedance spectroscopy of dielectric materials.
纳米颗粒金属属于颗粒电子系统这一总体类别，在该系统中可以研究电子关联、无序和有限尺寸效应之间的相互作用。纳米颗粒金属中的电荷传输主要由热辅助、顺序和相关隧穿控制，隧穿发生在数量与温度相关的金属颗粒上。在这里，我们研究了嵌入非晶碳（C）中的铂纳米颗粒构成的纳米颗粒铂的频率依赖电导率（交流电导率）。我们关注的是由一组涵盖一系列隧道耦合强度的样品所反映的绝缘体-金属转变绝缘侧的输运机制。在这种输运机制中，对交流电导率的极化贡献很小，预计自由电荷输运中的相关效应会特别显著。通过简单的集总电路分析，我们发现频率依赖性存在一种普遍行为，这种行为可以追溯到Pt/C的与温度相关的零频率电导率（直流电导率）。我们的结果与之前在非常弱耦合 regime下对纳米颗粒Pd/[公式：见原文]的研究相反，在该研究中，对交流电导率的极化贡献占主导。我们描述了纳米颗粒金属在介电材料近场阻抗光谱学中可能的未来应用。
