Universality of the electrical transport in granular metals.
Universality of the electrical transport in granular metals.
复制标题
粒状金属中电传输的普遍性。
DOI：
10.1038/srep29676
复制
发表时间：
2016-07-14
影响因子：
4.6
通讯作者：
Labarta A
中科院分区：
文献类型：
--
作者：
Bakkali H;Dominguez M;Batlle X;Labarta A
对颗粒金属中交流电输运的普遍性研究甚少，其标度规律的实际机制也没有得到很好的理解。以前的工作已经报道了Co-ZrO2颗粒金属在不同温度下的电容和介电损耗的缩放。然而，用于测量电导率谱的特征频率尚未得到讨论。本报告通过阻抗谱法提供了Pd-ZrO2颗粒薄膜在宽频率（11 Hz-2 MHz）和温度范围（40-180 K）下的普遍弛豫行为的明确证据。阻抗Z″和电模量M″虚部的频率依赖关系在频率ωmax处显示出各自的峰值，符合热激活定律，ωmax∝exp（T1/2）。此外，电导率的实部σ '符合Jonscher的普遍幂律，而电导率色散的起始点也符合ωmax。有趣的是，ωmax可以用作Z″，M″和σ '的标度参数，使得相应的光谱坍缩到单个主曲线上。总而言之，这些事实表明，时间-温度叠加原理适用于颗粒金属的交流电导，其中粒子之间的电子隧穿和电容路径相互竞争，表现出一种很好表征的普遍行为。
The universality of the ac electrical transport in granular metals has been scarcely studied and the actual mechanisms involved in the scaling laws are not well understood. Previous works have reported on the scaling of capacitance and dielectric loss at different temperatures in Co-ZrO2 granular metals. However, the characteristic frequency used to scale the conductivity spectra has not been discussed, yet. This report provides unambiguous evidence of the universal relaxation behavior of Pd-ZrO2 granular thin films over wide frequency (11 Hz–2 MHz) and temperature ranges (40–180 K) by means of Impedance Spectroscopy. The frequency dependence of the imaginary parts of both the impedance Z″ and electrical modulus M″ exhibit respective peaks at frequencies ωmax that follow a thermal activation law, ωmax ∝ exp(T1/2). Moreover, the real part of electrical conductivity σ′ follows the Jonscher’s universal power law, while the onset of the conductivity dispersion also corresponds to ωmax. Interestingly enough, ωmax can be used as the scaling parameter for Z″, M″ and σ′, such that the corresponding spectra collapse onto single master curves. All in all, these facts show that the Time-Temperature Superposition Principle holds for the ac conductance of granular metals, in which both electron tunneling and capacitive paths among particles compete, exhibiting a well-characterized universal behavior.