We offer a cross section of the numerous challenges and opportunities associated with the integration of large-scale battery storage of renewable energy for the electric grid. These challenges range beyond scientific and technical issues, to policy issues, and even social challenges associated with the transition to a more sustainable energy landscape.

The commissioning on 1 December 2017 of the Tesla-Neoen 100 MW lithium-ion grid support battery at Neoen’s Hornsdale wind farm in South Australia, at the time the world’s largest, has focused the attention of policy makers and energy professionals on the broader prospects for renewable energy storage. An adequate and resilient infrastructure for large-scale grid scale and grid-edge renewable energy storage for electricity production and delivery, either localized or distributed, is a crucial requirement for transitioning to complete reliance on environmentally protective human energy systems. Its realization will require a strong synergy between technological advances in variable renewable energy storage and the governance policies that promote and support them. We examine how existing regulations and governance policies focusing on large-scale batteries have responded to this challenge around the world. We offer suggestions for potential regulatory and governance reform to encourage investment in large-scale battery storage infrastructure for renewable energy, enhance the strengths, and mitigate risks and weaknesses of battery systems, including facilitating the development of alternatives such as hybrid systems and eventually the uptake of hydrogen fuel and storage.

Greener technologies for more efficient power generation, distribution, and delivery in sectors ranging from transportation and generic energy supply to telecommunications are quickly expanding in response to the challenge of climate change. Power electronics is at the center of this fast development. As the efficiency and resiliency requirements for such technologies can no longer be met by silicon, the research, development, and industrial implementation of wide bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) are progressing at an unprecedented pace. This issue of MRS Bulletin, although certainly not exhaustive, provides an overview of the pace and quality of research revolving around GaN and SiC power electronics, from the choice of substrates, film growth, devices, and circuits to examples of applications.

We introduce a novel approach to the synthesis of high-quality and highly uniform few-layer graphene on silicon wafers, based on solid source growth from epitaxial 3C-SiC films. Using a Ni/Cu catalytic alloy, we obtain a transfer-free bilayer graphene directly on Si(100) wafers, at temperatures potentially compatible with conventional semiconductor processing. The graphene covers uniformly a 2″ silicon wafer, with a Raman ID/IG band ratio as low as 0.5, indicative of a low defectivity material. The sheet resistance of the graphene is as low as 25 Ω/square, and its adhesion energy to the underlying substrate is substantially higher than transferred graphene. This work opens the avenue for the true wafer-level fabrication of microdevices comprising graphene functional layers. Specifically, we suggest that exceptional conduction qualifies this graphene as a metal replacement for MEMS and advanced on-chip interconnects with ultimate scalability.

The feasibility of a templated seedless approach for growing segmented p-i-n nanowires –based diodes based on selective epitaxial growth is demonstrated. Such diodes are the basic structure for a TunnelFET device. This approach has the potential for being easily scalable at a full-wafer processing, and there is no theoretical limitation for control on nanowires growth and properties when scaling down their diameters, as opposed to an unconstrained vapor-liquid-solid growth. Moreover, Si/SixGe1-x hetero-structures are implemented, showing that this can improve the TFET ON current not only thanks to the lowered barrier for the band-to-band source-channel tunneling, but additionally thanks to its lower thermal budget for growth, allowing for better control of the abruptness of the doping profile at the source-channel tunneling interface.

Nanoporous organosilicate films have been recently prepared using tetraalkylammonium cations in acid and basic media, outperforming other materials. Resulting films using basic medium were called zeolite-inspired low-k dielectrics. Here we study the dependence of the properties of these films on the used silica sources: methyltrimethoxy silane (MTMS) and tetraethyl orthosilicate (TEOS). A set of experiments varying the MTMS:TEOS ratio were prepared in acid medium and characterized. A textural, physico-chemical, mechanical, and electrical characterization of this series of experiments is presented.

Semiconductor nanowires are attractive nano- building blocks for microelectronics. However, the requirements for their manufacturing and application in the microelectronics industry are very demanding. Beyond compatibility with Si technology, full control on the characteristics of the grown wires (diameter, location, crystallinity, etc..), homogeneity on wafer –scale and reproducibility are essential. In this study we review critically important challenges for a controlled process of In –mediated growth of Si nanowires. First, we stress the importance of surface type for both particle catalysts and growth substrates. Both selection and preparation of such surfaces have large impact on growth, as they influence the initiation and the driving forces for the VLS growth mechanism. Moreover, wire characteristics such as morphology, crystalline quality and growth orientation appear more difficult to control when growing from particles with sizes below 40-50nm. This limitation arises as a result of both fundamental mechanisms and more specific constrains linked to the In-Si system.

A few perspectives are given for the achievement of a controlled Si nanowire growth in a Si –technology compatible fashion.

The use of Au nanoparticles as catalysts for growth of Si nanowires poses fundamental reliability concerns for applications in Si semiconductor technology. In this work we show that the choice of catalysts can be broadened when the need for catalytic precursor dissociation is eliminated. However, the requirements for selective deposition in a gas phase transport -limited regime become stringent. When competing deposition of amorphous Si can bury the particles faster than the incubation time for VLS growth, no nanowire growth will be initiated. We show that the use of a catalyst such as In, already in a liquid form at the growth temperature, is effective. Therefore, the choice of VLS catalysts among the low melting point metals from the III, IV and V groups is suggested.

29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was employed to characterize short-range atomic structure modifications to low k dielectric films that were subjected to post-deposition plasma exposure or UV curing. Comparison of spectra from single thick depositions of a CVD low k film (k∼3.0) with sequential thin depositions of the same film revealed ∼3% increase in Si-O crosslinking that was attributed to interfacial plasma damage. Comparison of a second CVD low k film (k∼3.0) before and after UV curing revealed ∼11% increase in Si-O crosslinking with commensurate losses of Si-OH and Si-CH3 groups. UV curing was believed to result in bulk modification. This crosslinking was found to increase the Young's modulus of the film from 11 to 16 GPa as measured on 700 nm films by nanoindentation. NMR analysis was found to provide significant information beyond that provided by FTIR but required special sample preparation and extensive data collection.