Liquid-Liquid Interface-Assisted Self-Assembly of Ag-Doped ZnO Nanosheets for Atomic Switch Application.

Developing facile and inexpensive methods for obtaining large-area two-dimensional semiconducting nanosheets is highly desirable for mass-scale device application. Here, we report a method for producing uniform and large-area films of a Ag-doped ZnO (AZO) nanosheet network via self-assembly at the hexane-water interface by controlling the solute/solvent ratio. The self-assembled film comprises of uniformly tiled nanosheets with size ∼1 µm and thicknesses∼60-100 nm. Using these films in a Pt/AZO/Ag structure, an atomic switch operation is realized. The switching mechanism is found to be governed by electrochemical metallization with nucleation as the rate-limiting step. Our results establish the protocol for large-scale device applications of AZO nanosheets for exploring advanced atomic switch-based neuromorphic systems.

Deciphering pressure-induced nanoarchitectonics in a monolayer of heterocoronene-based discotics at air-water and air-solid interfaces.

Understanding and control of molecular alignment at the nanoscale in self-assembled supramolecular structures is a prerequisite for the subsequent exploitation of molecules in functional devices. Here, we have clarified the surface-pressure induced molecular nanoarchitectures in a monolayer of a heterocoronene-based discotic liquid crystal (DLC) at air-water and air-solid interfaces using surface manometry, real-time Brewster angle microscopy, and real-space atomic force microscopy (AFM). Chloroform-spread DLCs at a concentration of ∼108 µM exhibit floating domains at the air-water interface comprising small aggregates of edge-on stacked molecules interacting via peripheral alkyl chains. Detailed analysis of surface manometry and relaxation measurements reveal that, upon compression, these domains coalesce to form a coherent monolayer which then undergoes irreversible structural transformations via mechanisms such as monolayer loss due to desorption and localized nucleation of defects. AFM images of the films transferred on a hydrophilic substrate reveal that with increasing surface-pressure, the nanoscale structure of the monolayer transforms from randomly oriented nanowires to tightly-packed nanowire domains, and finally to fragmented wire segments which diffuse locally above the film. These results provide a facile method for the preparation of compact, two-dimensional films of ambipolar DLC molecules with a tunable nanoarchitecture which will be crucial for their applications in nanoscale electronic devices.