（Ag，Mo）$_x$（SnO $_2$）$_{1-x}$薄膜介电区的颗粒跳跃导电
Granular hopping conduction in (Ag,Mo)$_x$(SnO$_2$)$_{1-x}$ films in the dielectric regime
摘要：
我们研究了两个系列的Ag $_{x}$（SnO $_2$）$_{1-x}$和Mo $_{x}$（SnO $_2$）$_{1-x}$颗粒膜的电导率$σ(T)$的温度依赖性，其中$x$是金属的体积分数。在前一系列中的金属颗粒具有近似球形的形状，而在后一系列中包含许多小的亚结构。在这两个系列的薄膜，我们已经观察到的$σ\propto \exp[-(T_0/T)^m]$温度依赖性，与$m\,\simeq\,1/2$，在宽$T$范围从2到80（100）K，其中$T_0$是一个特征温度。我们的$σ$（$T$）的结果解释的Abeles-Sheng模型，该模型考虑了金属颗粒的结构效应。随着$x$的减小，颗粒间最佳分离度（$s_{m}$）和充电能量（$E_{c}$）的提取值略有增加。在Abeles-Sheng模型中定义的参数$C(x)$的变化与仅取决于$x$和绝缘基体的介电常数的简化表达式一致。当温度升高到100 K以上时，观察到热涨落诱导的隧穿导电过程的交叉。
英文摘要：
We have studied the temperature dependence of conductivity, $σ(T)$, in two series of Ag$_{x}$(SnO$_2$)$_{1-x}$ and Mo$_{x}$(SnO$_2$)$_{1-x}$ granular films lying below the percolation threshold, where $x$ is the metal volume fraction. The metal grains in the former series have approximately spherical shape, whereas in the latter series contain numerous small substructures. In both series of films, we have observed the $σ\propto \exp[-(T_0/T)^m]$ temperature dependence, with $m\,\simeq\,1/2$, over the wide $T$ range from 2 to 80 (100) K, where $T_0$ is a characteristic temperature. Our $σ$($T$) results are explained in term of the Abeles-Sheng model which considers the structural effect of metal grains. The extracted values of the optimal separation between grains ($s_{m}$) and the charging energy ($E_{c}$) slightly increase with decreasing $x$. The variation of the parameter $C(x)$, defined in the Abeles-Sheng model, is in consistency with a simplified expression which depends only on $x$ and the dielectric constant of the insulating matrix. As the temperature is increased to above $\sim$\,100 K, a crossover to the thermally fluctuation-induced tunneling conduction processes is observed.
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