2021/01/19 by Alessandro Kovtun, Andrea Candini, Anna Vianelli +13
Materials Science · Physics and Astronomy · #2D Materials and Applications #Charge (physics) #Charge carrier #Chemical physics #Condensed matter physics #Graphene #Graphene research and applications #Heterojunction #Materials science #Molecule #Nanosheet #Nanotechnology #Optoelectronics #Oxide #Percolation (cognitive psychology) #Physics #Thermal properties of materials #Thin film #cond-mat.mes-hall #cond-mat.mtrl-sci #van der Waals force
paper · pdf · doi:10.1021/acsnano.0c07771
published as ACS Nano 2021, 15, 2, 2654 2667
openalex publication_date 2021/01/19 · arxiv created 2021/02/02 · arxiv updated 2021/03/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Large area van der Waals (vdW) thin films are assembled materials consisting of a network of randomly stacked nanosheets. The multiscale structure and the two-dimensional (2D) 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 Ω·m. We systematically observe a clear transition between two different regimes at a critical temperature T *: Efros–Shklovskii variable-range hopping (ES-VRH) below T * and power law behavior above. First, we demonstrate that the two regimes are strongly correlated with each other, both depending on the charge localization length ξ, calculated by the ES-VRH model, which corresponds to the characteristic size of overlapping sp 2 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-one-dimensional nanofillers with length ξ, 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.