Fabrication of periodic arrays of metallic nanoparticles by block copolymer templates on HfO2 substrates

Electron Transport in Discontinuous Metal Thin Films

The structure and basic experimental electrical properties of vacuum evaporated discontinuous (island) metal thin films of discrete metal nanoparticles on insulating substrates are briefly reviewed. Then the widely accepted Neugebauer and Webb (N&W) electrostatically activated electron tunneling conduction model is covered (with enhancements) before the numerous discrepancies between this model and experimental observations are identified, e.g. minimal substrate bias effect, non-linear field distribution, anomalous AC effects, asymmetrical contact effects, and switching. A modified model, based on contact electron injection and extraction, and computer simulations are introduced which explain these discrepancies at a qualitative level. However, quantitative experimental verification of the model is not possible without stable, reproducible films of known structures. The paper concludes with a review of possible preparation techniques which could yield satisfactory samples, especially self-assembly of organically protected metal nanoparticles. One of these has already demonstrated electrostatically activated conduction.

Rectangular Cylinders Formed by Compositionally Bidisperse ABC Triblock Terpolymer Blends: A Self-Consistent Field Theory Study

Compared with traditional cylinders that have circular cross-sections, cylinders with rectangular cross-sections can endow nanomaterials with various novel optical properties and functions. In this work, the formation of the rectangular cylinders self-assembled by compositionally bidisperse ABC triblock terpolymer blends has been investigated via numerical simulations based on self-consistent field theory. The specially designed blending systems are composed of two types of linear ABC triblock terpolymers that have the same total chain lengths and the middle B block chain lengths, but different chain lengths of the side A/C blocks. By tuning the chain length fractions and the interactions between different blocks, rectangular cylinders with a fourfold symmetry pattern were successfully obtained in our simulations. Each rectangular phase domain is self-assembled together by the short and long side blocks of the same species. The simulation results indicate that the selective aggregation of the short side blocks determines the formation of the rectangular cylindrical phase, i.e., the short side blocks prefer to aggregate at the four corners within a rectangular cylindrical phase domain. This simulation result reveals a formation mechanism that is different from the mechanism proposed in previous experiments [Asai ACS Macro Lett., 2014, 3, 166-169]. Moreover, under different middle B block chain length fractions, phase diagrams as a function of the interaction parameter between different blocks and the short side block chain length fraction have been constructed. The phase diagrams show that the parameter window of the rectangular cylinders is considerably expanded by increasing the chain length fraction of the middle B blocks. Our simulation works can provide a theoretical basis for molecular design to regulate and fabricate nanomaterials with nontraditional phase domains in future experiments.

Tailored Surfaces/Assemblies for Molecular Plasmonics and Plasmonic Molecular Electronics

Molecular plasmonics uses and explores molecule-plasmon interactions on metal nanostructures for spectroscopic, nanophotonic, and nanoelectronic devices. This review focuses on tailored surfaces/assemblies for molecular plasmonics and describes active molecular plasmonic devices in which functional molecules and polymers change their structural, electrical, and/or optical properties in response to external stimuli and that can dynamically tune the plasmonic properties. We also explore an emerging research field combining molecular plasmonics and molecular electronics.