In this review, we present an update on the methods for screening 2D materials suitable for valleytronic applications. We begin with an introduction to the field highlighting some of the latest findings and seminal works. Then we provide a brief background on the physics of valley- and layer- pseudospins in layered 2D materials such as transition metal dichalcogenides. This is followed by a detailed survey of a number of key techniques commonly employed to elucidate valley properties in such materials, highlighting in particular their capability for discriminating valley pseudospins, their key advantages and current limitations. Finally, we conclude by summarising the state-of-the-art assessing materials for valleytronic applications and point the reader to the current open questions that could have critical influence on the technological impact that may be derived from such materials.
High-k, low leakage thin films are crucial components for dynamic random access memory (DRAM) capacitors with high storage density and a long storage lifetime. In this work, we demonstrate a method to increase the dielectric constant and decrease the leakage current density of atomic layer deposited BaTiO3 thin films at low process temperature (250 °C) using postdeposition remote oxygen plasma treatment. The dielectric constant increased from 51 (as-deposited) to 122 (plasma-treated), and the leakage current density decreased by 1 order of magnitude. We ascribe such improvements to the crystallization and densification of the film induced by high-energy ion bombardments on the film surface during the plasma treatment. Plasma-induced crystallization presented in this work may have an immediate impact on fabricating and manufacturing DRAM capacitors due to its simplicity and compatibility with industrial standard thin film processes.
Although Si acts as an electrical semiconductor, it has properties of an optical dielectric.Here, we revisit the behavior of Si as a plasmonic metal. This behavior was previously shown to arise from strong interband transitions that lead to negative permittivity of Si across the ultra-violet spectral range. However, so far, few have studied the plasmonic characteristics of Si, particularly in its nanostructures. In this paper, we report localized plasmon resonances in Si nanostructures and the observation of plasmon hybridization in the UV (~250 nm wavelength). In addition, simulation results show that Si nanodisk dimers can achieve a local intensity enhancement greater than ~500-fold in a 1 nm gap. Lastly, we investigate hybrid Si-Al nanostructures to achieve sharp resonances in the UV, due to the coupling between plasmon resonances supported by Si and Al nanostructures. These results will have potential applications in the UV range, such as nanostructured devices for spectral filtering, plasmon enhanced Si photodetectors, interrogation of molecular chirality, and catalysis. It could have significant impact on UV photolithography on patterned Si structures.
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