Partnerships and collaboration drive innovative graduate training in materials informatics.

Holistic and intentional training prepares next-generation materials informatics leaders and workforce for expedited materials discovery and design.

Strain-Driven Faceting of Graphene-Catalyst Interfaces.

The interfacial interaction of 2D materials with the substrate leads to striking surface faceting affecting its electronic properties. Here, we quantitatively study the orientation-dependent facet topographies observed on the catalyst under graphene using electron backscatter diffraction and atomic force microscopy. The original flat catalyst surface transforms into two facets: a low-energy low-index surface, e.

Controlling Rotation of Two-Dimensional Material Flakes.

Interlayer rotational alignment in van der Waals (vdW) structures of two-dimensional (2D) materials couples strongly to electronic properties and, therefore, has significant technological implications. Nevertheless, controlling the rotation of an arbitrary 2D material flake remains a challenge in the development of rotation-tunable electronics, for the emerging field of twistronics. In this article, we reveal a general moiré-driven mechanism that governs the interlayer rotation.

Moiré-templated strain patterning in transition-metal dichalcogenides and application in twisted bilayer MoS.

To take full advantage of the electronic properties of transition-metal dichalcogenides and their vdW layered structures, it will be necessary to control the local electronic structure, on which the effect of lattice deformation is significant. Nevertheless, a general approach to programming nanoscale morphology in TMD materials, which would permit local strain engineering, has proven elusive. In this work, we propose a general moiré-templated nanoscale morphology engineering method based on bilayer TMDs.

Strain Modulation of Graphene by Nanoscale Substrate Curvatures: A Molecular View.

Spatially nonuniform strain is important for engineering the pseudomagnetic field and band structure of graphene. Despite the wide interest in strain engineering, there is still a lack of control on device-compatible strain patterns due to the limited understanding of the structure-strain relationship. Here, we study the effect of substrate corrugation and curvature on the strain profiles of graphene via combined experimental and theoretical studies of a model system: graphene on closely packed SiO nanospheres with different diameters (20-200 nm).

Direct Electrical Probing of Periodic Modulation of Zinc-Dopant Distributions in Planar Gallium Arsenide Nanowires.

Selective lateral epitaxial (SLE) semiconductor nanowires (NWs), with their perfect in-plane epitaxial alignment, ability to form lateral complex p-n junctions in situ, and compatibility with planar processing, are a distinctive platform for next-generation device development. However, the incorporation and distribution of impurity dopants in these planar NWs via the vapor-liquid-solid growth mechanism remain relatively unexplored. Here, we present a detailed study of SLE planar GaAs NWs containing multiple alternating axial segments doped with Si and Zn impurities by metalorganic chemical vapor deposition.

Towards do-it-yourself planar optical components using plasmon-assisted etching.

In recent years, the push to foster increased technological innovation and basic scientific and engineering interest from the broadest sectors of society has helped to accelerate the development of do-it-yourself (DIY) components, particularly those related to low-cost microcontroller boards. The attraction with DIY kits is the simplification of the intervening steps going from basic design to fabrication, albeit typically at the expense of quality. We present herein plasmon-assisted etching as an approach to extend the DIY theme to optics, specifically the table-top fabrication of planar optical components.

Strain Relaxation in CVD Graphene: Wrinkling with Shear Lag.

We measure uniaxial strain fields in the vicinity of edges and wrinkles in graphene prepared by chemical vapor deposition (CVD), by combining microscopy techniques and local vibrational characterization. These strain fields have magnitudes of several tenths of a percent and extend across micrometer distances. The nonlinear shear-lag model remarkably captures these strain fields in terms of the graphene-substrate interaction and provides a complete understanding of strain-relieving wrinkles in graphene for any level of graphene-substrate coherency.

Imbricate scales as a design construct for microsystem technologies.

Spatially overlapping plates in tiled configurations represent designs that are observed widely in nature (e.g., fish and snake scales) and man-made systems (e.

Theory for optimal design of waveguiding light concentrators in photovoltaic microcell arrays.

Efficiency of ultrathin flexible solar photovoltaic silicon microcell arrays can be significantly improved using nonimaging solar concentrators. A fluorophore is introduced to match the solar spectrum and the low-reflectivity wavelength range of Si, reduce the escape losses, and allow the nontracking operation. In this paper we optimize our solar concentrators using a luminescent/nonluminescent photon transport model.

Flexible concentrator photovoltaics based on microscale silicon solar cells embedded in luminescent waveguides.

Unconventional methods to exploit monocrystalline silicon and other established materials in photovoltaic (PV) systems can create new engineering opportunities, device capabilities and cost structures. Here we show a type of composite luminescent concentrator PV system that embeds large scale, interconnected arrays of microscale silicon solar cells in thin matrix layers doped with luminophores. Photons that strike cells directly generate power in the usual manner; those incident on the matrix launch wavelength-downconverted photons that reflect and waveguide into the sides and bottom surfaces of the cells to increase further their power output, by more than 300% in examples reported here.

Multidimensional architectures for functional optical devices.

Materials exhibiting multidimensional structure with characteristic lengths ranging from the nanometer to the micrometer scale have extraordinary potential for emerging optical applications based on the regulation of light-matter interactions via the mesoscale organization of matter. As the structural dimensionality increases, the opportunities for controlling light-matter interactions become increasingly diverse and powerful. Recent advances in multidimensional structures have been demonstrated that serve as the basis for three-dimensional photonic-bandgap materials, metamaterials, optical cloaks, highly efficient low-cost solar cells, and chemical and biological sensors.

Three-dimensional nanostructures formed by single step, two-photon exposures through elastomeric penrose quasicrystal phase masks.

We describe the fabrication of unusual classes of three-dimensional (3D) nanostructures using single step, two-photon exposures of photopolymers through elastomeric phase masks with 5-fold, Penrose quasicrystalline layouts. Confocal imaging, computational studies, and 3D reconstructions reveal the essential aspects of the flow of light through these quasicrystal masks. The resulting nanostructures show interesting features, including quasicrystalline layouts in planes parallel to the sample surfaces, with completely aperiodic variations through their depths, consistent with the optics.