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Harnessing hot electrons and holes resulting from the decay of localized surface plasmons in nanomaterials has recently led to new devices for photovoltaics, photocatalysis and optoelectronics. Properties of hot carriers are highly tunable and in this work we investigate their dependence on the material, size and environment of spherical metallic nanoparticles. In particular, we carry out theoretical calculations of hot carrier generation rates and energy distributions for six different plasmonic materials (Na, K, Al, Cu, Ag and Au). The plasmon decay into hot electron-hole pairs is described via Fermi's Golden Rule using the quasistatic approximation for optical properties and a spherical well potential for the electronic structure. We present results for nanoparticles with diameters up to 40 nm, which are embedded in different dielectric media. We find that small nanoparticles with diameters of 16 nm or less in media with large dielectric 1 arXiv:1802.05096v1 [cond-mat.mtrl-sci] 14 Feb 2018 constants produce most hot carriers. Among the different materials, Na, K and Au generate most hot carriers. We also investigate hot-carrier induced water splitting and find that simple-metal nanoparticles are useful for initiating the hydrogen evolution reaction, while transition-metal nanoparticles produce dominantly holes for the oxygen evolution reaction. Keywordshot electrons, plasmon decay, nanoparticles, water splitting, nanophotonics Energetic or "hot" electrons and holes produced by the decay of localized surface plasmons (LSP) in metallic nanostructures have recently generated much excitement. They can be harnessed in optoelectronic devices, such as photodetectors, or for solar energy conversion, i.e. in photocatalytic or photovoltaic devices. 1-8 For example, Mukherjee et al. observed that plasmon-induced hot electrons can trigger H 2 dissociation reactions on the surface of gold nanoparticles. 9 An important advantage of nanoplasmonic devices compared to traditional systems is their tunability: their optical and electronic properties depend sensitively on the nanoparticle size and shape, but also on the nanoparticle material and its environment. 10-15To guide experimental progress and identify nano-devices with favorable hot-carrier properties, a detailed theoretical understanding of the physico-chemical processes that govern hot-carrier generation is needed. However, developing such a theory is challenging because of the large size of experimentally relevant nanoparticles. Atomistic ab initio calculations are currently only feasible for metallic clusters and very small nanoparticles. 5,16,17 To model properties of experimentally relevant nanoparticles with radii of 10 nm or more, two different strategies have been employed. In many calculations, simplified models for the electronic structure of the nanoparticle are used, such as jellium models or non-interacting electron models. 18-21 For example, Manjavacas et al. employed a spherical well model to simulate hot-carrier generation in silver nanoparticles with di...

Computational design can accelerate the discovery of new materials with tailored properties, but applying this approach to plasmonic nanoparticles with diameters larger than a few nanometers is challenging as atomistic first-principles calculations are not feasible for such systems. In this paper, we employ a recently developed material-specific approach that combines effective mass theory for electrons with a quasistatic description of the localized surface plasmon to identify promising bimetallic core-shell nanoparticles for hot-electron photocatalysis. Specifically, we calculate hot-carrier generation rates of 100 different core-shell nanoparticles and find that systems with an alkali-metal core and a transition-metal shell exhibit high figures of merit for water splitting and are stable in aqueous environments. Our analysis reveals that the high efficiency of these systems is related to their electronic structure, which features a two-dimensional electron gas in the shell. Our calculations further demonstrate that hot-carrier properties are highly tunable and depend sensitively on core and shell sizes. The design rules resulting from our work can guide experimental progress towards improved solar energy conversion devices.

Chalcogenide phase change materials (PCMs) are truly remarkable compounds whose unique switchable optical and electronic properties have fueled an explosion of emerging applications in electronics and photonics. Key to any application is the ability of PCMs to reliably switch between crystalline and amorphous states over a large number of cycles. While this issue has been extensively studied in the case of electronic memories, current PCM-based photonic devices show limited endurance. This review discusses the various parameters that impact crystallization and re-amorphization of several PCMs, their failure mechanisms, and formulate design rules for enhancing cycling durability of these compounds.

Packaging of photonic integrated circuit (PIC) chips is an essential and critical step before they can be integrated into functional optoelectronic systems. Photonic packaging is however often a major barrier impeding scalable deployment of PIC technologies given its high cost and limited throughput. This perspective addresses the technical challenges and discusses promising strategies and research directions to overcome the "packaging bottleneck".