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arXiv 2102.01488cond-mat.mes-hallcond-mat.mtrl-sci
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范德瓦尔斯薄膜中的多尺度电荷输运:还原氧化石墨烯的实例研究

Multiscale charge transport in van der Waals thin films: reduced graphene oxide as case study

Alessandro Kovtun, Andrea Candini, Anna Vianelli, Alex Boschi, Simone Dell Elce, Marco Gobbi, Kyung Ho Kim, Samuel Lara Avila, Paolo Samori, Marco Affronte, And… 展开作者

Alessandro Kovtun, Andrea Candini, Anna Vianelli, Alex Boschi, Simone Dell Elce, Marco Gobbi, Kyung Ho Kim, Samuel Lara Avila, Paolo Samori, Marco Affronte, Andrea Liscio, Vincenzo Palermo

摘要:

大面积范德华(vdW)薄膜是由随机堆叠的纳米片网络组成的组装材料。构建块的多尺度结构和二维性质意味着界面自然地在这种薄膜的电荷传输中起关键作用。虽然单个或几个堆叠的纳米片(即vdW异质结构)一直是密集工作的主题,但对电荷如何通过多层,更无序的网络行进知之甚少。在这里,我们报告了随机堆叠的还原氧化石墨烯2D纳米片网络给出的原型系统的全面研究,其化学和几何性质可以独立控制,允许探索从单个纳米片到数十亿个纳米片的纳米网络,室温电阻率从10-5到10-1欧姆米。我们系统地观察到在临界温度T* 下两种不同制度之间的明显转变:低于T* 的Efros-Shklovskii可变范围跳跃(ESVRH)和高于T* 的幂律(PL)行为。首先,我们证明了这两个制度是强烈相关的彼此,都取决于电荷局域化长度xi,计算ES-VRH模型,这对应于重叠的sp2域属于不同的纳米片的特征尺寸。因此,我们提出了一个微观模型描述的电荷传输作为一个几何相变,给出的金属-绝缘体过渡与渗透的准一维纳米填料与长度为xi,表明网络的电荷传输行为是有效的所有的几何形状和缺陷的纳米片,最终提出了一个广义的描述vdW和无序薄膜。

英文摘要:

Large area van der Waals (vdW) thin films are assembled materials consisting of a network of randomly stacked nanosheets. The multi-scale structure and the two-dimensional nature of the building block mean that interfaces naturally play a crucial role in the charge transport of such thin films. While single or few stacked nanosheets (i.e. vdW heterostructures) have been the subject of intensive works, little is known about how charges travel through multilayered, more disordered networks. Here we report a comprehensive study of a prototypical system given by networks of randomly stacked reduced graphene oxide 2D nanosheets, whose chemical and geometrical properties can be controlled independently, permitting to explore percolated networks ranging from a single nanosheet to some billions with room temperature resistivity spanning from 10-5 to 10-1 ohm m. We systematically observe a clear transition between two different regimes at a critical temperature T*: Efros-Shklovskii variable range hopping (ESVRH) below T* and power law (PL) behavior above. Firstly, we demonstrate that the two regimes are strongly correlated with each other, both depending on the charge localization length xi, calculated by ES-VRH model, which corresponds to the characteristic size of overlapping sp2 domains belonging to different nanosheets. Thus, we propose a microscopic model describing the charge transport as a geometrical phase transition, given by the metal-insulator transition associated with the percolation of quasi-1D nanofillers with length xi, showing that the charge transport behavior of the networks is valid for all geometries and defects of the nanosheets, ultimately suggesting a generalized description on vdW and disordered thin films.

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