Archived highlights

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Alloy Engineering Cleans Up a New Class of Semiconductors
Simulations provide a recipe based on mixing of two materials (“alloying”) to remove defect levels that limit the optimal electronic and optoelectronic properties of semiconductors. “Alloy Engineering of Defect Properties in Semiconductors: Suppression of Deep Levels in Transition-Metal Dichalcogenides” (highlight slide) Huang et. al., Phys. Rev. Lett. (2015) |
Nanofabrication with Single Atomic Plane Precision: Atomic-Level Sculpting of Crystalline Oxides
Epitaxial nanostructures of complex oxide are created by e-beam individual crystallization with single atomic plane precision and arbitrary shapes. ”Atomic-level sculpting of crystalline oxides: towards bulk nanofabrication with single atomic plane precision” (highlight slide) Jesse et al., Small (2015)| DOI: 10.1002/smll.201502048
A simple, optical method to determine how two-dimensional layers are stacked in a crystal
An optical method (Terahertz Raman spectroscopy) was developed for fast remote screening of layer stacking in new two-dimensional (2D) materials, which is orders of magnitude faster than conventional electron microscopy. “Low-Frequency Raman Fingerprints of Two-Dimensional Metal Dichalcogenide Layer Stacking Configuration” (highlight slide) Puretzky et al., ACS Nano (2015) | DOI:10.1021/acsnano.5b01884
High-Performance Flexible Perovskite Solar Cells
High performance and mechanically-robust crystalline perovskite solar cells were fabricated on flexible substrates by ultrasonic spray-coating (USC) and pulsed photonic curing processes. “High-Performance Flexible Perovskite Solar Cells by Using a Combination of Ultrasonic Spray-Coating and Low Thermal Budget Photonic Curing” (highlight slide) Das et al., ACS Photonics (2015) | DOI: 10.1021/acsphotonics.5b00119
A layered, environmentally friendly material (CuInP2S6) demonstrated to be polar at room temperature
Scanning probe techniques provide the first direct evidence for built-in electric fields in the 2D material, CuInP2S6. “CuInP2S6 - Room Temperature Layered Ferroelectric” (highlight slide) Belianinov et al., Nano Lett. (2015) | DOI: 10.1021/acs.nanolett.5b00491
Quadrupling the Activity of Core-Shell Catalyst Particles
Electron microscopy reveals that lattice distortions in Pd-Pt core-shell catalyst particles lead to four- to eight-fold enhancements in activity for oxygen reduction. “Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability toward oxygen reduction” (highlight slide) Wang et al., Nature Commun. (2015) | DOI: 10.1038/ncomms8594
Calculations Reveal the Nature of Exotic Electron Pairing States in an Iron-based Superconductor
Microscopic calculations of an iron-based superconductor demonstrate that exotic eta-pairs with finite center of mass momentum contribute to the superconducting condensate with even parity and time reversal symmetry. “Glide-Plane Symmetry and Superconducting Gap Structure of Iron-Based Superconductors” (highlight slide) Wang et al., Phys. Rev. Lett. (2015) | DOI: 10.1103/PhysRevLett.114.107002
Control of composition and strain leads to useful properties in an environmentally friendly silicide
Metastable α-FeSi2, a phase with useful ferromagnetic and transport properties, was epitaxially stabilized as a thin film on silicon.  Density functional calculations describe the unusual electronic structure. “Ferromagnetism and Nonmetallic Transport of Thin-Film α-FeSi2: A Stabilized Metastable Material” (highlight slide) Cao et al., Phys. Rev. Lett. (2015) | DOI: 10.1103/PhysRevLett.114.147202
Tiny changes have huge impact – switching a material’s magnetic strength with a voltage
By applying a tiny electric field at room temperature to an oxide crystal, the magnetic properties of a coating (FeRh film) on this crystal can be switched, demonstrating a new, giant electro-resistance effect. “Large resistivity modulation in mixed-phase metallic systems” (highlight slide) Lee, et al., Nature Commun. (2015) | DOI: 10.1038/ncomms6959
In-situ Environment Shines Light and Neutrons on Structure–Function Evolution of Polymers
A unique environmental chamber enables a new level of manipulation of polymers in solution and in thin films, and used it to explore structure and function of materials while they were being made (“in situ”). “Controlling Molecular Ordering in Solution-State Conjugated Polymers” Zhu et. al., Nanoscale (2015) | DOI: 10.1039/c5nr02037a and “Peculiarity of Two Thermodynamically-Stable Morphologies and Their Impact on the Efficiency of Small Molecule Bulk Heterojunction Solar Cells” (highlight slide) Herath, et al., Scientific Reports (2015) | DOI:10.1038/srep13407
Nanotextured Micropillars Accelerate Ice/Water Removal from Surfaces for Heat Exchangers
Superhydrophobic surfaces consisting of nano-textured micropillars induce sideways jumping of water droplets, which can rapidly remove water condensate from the surface in a “chain reaction”. “Self-Propelled Sweeping Removal of Dropwise Condensate” (highlight slide) Qu, et al., App. Phys. Lett. (2015) | DOI: 10.1063/1.4921923
New chemistry for graphene
Theoretical simulations identify a tunable and new type of chemical bonding in graphene-based materials. “Nitrogen-Doping Enables Covalent-Like π−π Bonding between Graphenes” (highlight slide) Tian, et al., Nano Lett. (2015) | DOI: 10.1021/acs.nanolett.5b01940
Exquisite Control During Growth to Create Complex Oxide Microstructures
A robust solution-phase process to synthesize complex silica and silica–titania hybrid microstructures was developed to build complex hybrid structures. "Step-by-Step Growth of Complex Oxide Microstructures" (highlight slide) Datskos, et al., Angew. Chem. Int. Ed. (2015) | DOI: 10.1002/anie.201503777
Activating Grain Boundaries in Perovskite Solar Cells
A new morphology for perovskite solar cells was realized that activates vertical grain boundaries between single-crystalline grains to enhance the collection and transport of photogenerated charges. “Perovskite Solar Cells with Near 100% Internal Quantum Efficiency Based on Large Single Crystalline Grains and Vertical Bulk Heterojunctions” (highlight slide) B. Yang et al., J. Am. Chem. Soc. (2015) | DOI: 10.1021/jacs.5b03144


Computations Shine Light on a Single-Layer Sheet of Zinc Selenide
Computer simulations identify a unique sheet of zinc selenide (ZnSe) composed of a three atom thick single-layer that has a large enhancement of the electronic band gap.
“A Novel and Functional Single-Layer Sheet of ZnSe” (highlight slide)
J. Zhou et al., ACS Appl. Mater. Interfaces (2015) | DOI:10.1021/am505655m
Heat flow between a tip and a surface depends on atomic scale properties of the surface
Tuning the electronic properties of a surface increases the thermally induced voltage between a sharp tip and a clean surface ten-fold.
“Surface-State Enhancement of Tunneling Thermopower on the Ag(111) Surface” (highlight slide)
P. Maksymovych et al., ACS Nano (2015) | DOI:10.1021/nn506123g
Tuning friction at the nanoscale
Electrically-induced condensation of lubricant (water) from air controls friction of surfaces.
“Nanoscale Lubrication of Ionic Surfaces Controlled via Strong Electric Field” (highlight slide)
E. Stelcov et al., Scientific Reports (2015) | DOI: 10.1038/srep08049
Untangling How Crystals Stack
Bilayers of GaSe were grown directly onto transmission electron microscopy grids. This made it possible to study how two layers stack, such as to understand the importance and consequences of van der Waals interactions.
"Revealing the Preferred Interlayer Orientations and Stackings of Two-Dimensional Bilayer Gallium Selenide Crystals" (highlight slide)
X. Li et al., Angew. Chem. Int. Ed. (2015) | DOI:10.1002/anie.201409743
“Googling” the Wealth of Information Available from Microscopy
A “general mode” of atomic force microscopy is introduced, in which all of the data describing the motion of the tip is collected. This enables a more un-biased, thorough analysis of the data after it has been collected. The use of a supercomputer (Titan) make such analysis possible in real time.
"Complete information acquisition in dynamic force microscopy" (highlight slide)
A. Belianinov et al., Nat. Commun. (2015) | DOI:10.1038/ncomms7550
Watching what happens in an operating battery, at the nanoscale
A new microscopy technique (in situ electrochemical scanning transmission electron microscopy, or in situ ec-S/TEM) allows scientists to observe how the components of a Li-ion battery change while the battery is used.
"Nanoscale Imaging of Fundamental Li Battery Chemistry: Solid-Electrolyte Interphase Formation and Preferential Growth of Lithium Metal Nanoclusters" (highlight slide)
R. L. Sacci et al., Nano Lett. (2015)  | DOI: 10.1021/nl5048626
Controlling Leidenfrost Droplets Directionality by Tuning the Height of the Surface Features  
Directionality of a Leidenfrost droplet can be controlled by varying the height and the length scale of the surface features. 
“Length Scale of Leidenfrost Ratchet Switches Droplet Directionality” (highlight slide)
R.L. Agapov et al., Nanoscale (2014) | DOI: 10.1039/C4NR02362E
Big-Data Approach to Surface Diffraction Data for Film Growth
Multivariate statistical analysis is applied to surface electron diffraction data to unravel hidden epitaxial film growth processes.
“Big-data Reflection High Energy Electron Diffraction Analysis for Understanding Epitaxial Film Growth Processes” (highlight slide)
R. K. Vasudevan et al., ACS Nano (2014) | DOI: 10.1021/nn504730n
Ion Transport and Softening in a Polymerized Ionic Liquid
The Dissociation of ions resulting from the presence of an applied electric field leads to novel engagement between conductivity and structural properties for polymerized ionic liquids.
“Ion transport and softening in a polymerized ionic liquid” (highlight slide)
R. Kumar et al., Nanoscale (2014) | DOI: 10.1039/c4nr05491a
A Glimpse into the Formation of a Molecular Bottlebrush During Polymerization Reactions
Chemical building blocks are joined together as part of a complicated chemical synthesis while experimentally and computationally observing the process that underwent three conformational changes to produce a complex “bottlebrush” shape.
“Structural Evolution of Poly(lactide) Molecular Bottlebrushes” (highlight slide)
S-K. Ahn et al., ACS Macro Letters (2014) | DOI: 10.1021/mz5003454
Super Stable Ceramic Opens New Horizons for High-Energy Lithium Batteries
An excellent stability of the lithium ion conducting ceramic electrolyte Li7La3Zr2O12 in neutral and strong basic aqueous solutions is observed. The identification of such electrolyte materials with excellent stability across a wide pH range speeds the advent of batteries that exceed conventional lithium-ion technology in both energy density and operating life.
“Excellent Stability of a Li-Ion-Conducting Solid Electrolyte upon Reversible Li+/H+ Exchange in Aqueous Solutions” (highlight slide)
C. Ma et al., Angewandte Chemie International Edition (2014) | DOI: 10.1002/anie.201408124
Arbitrary Rotation of Bits Creates New Options for Data Storage
The presence of small nanoscale domains makes it possible to rotate the ferroelectric polarization of a thin film in an arbitrary, but deterministic, direction. Controlled manipulation of polarization to any angle allows increased information densities for ferroelectric memory devices.
“Deterministic arbitrary switching of polarization in a ferroelectric thin film” (highlight slide)
R.K. Vasudevan et al., Nature Communications (2014) | DOI: 10.1038/ncomms5971

Confined Nanoparticle Evaporation: Creating Patterned 2D Metal Chalcogenides
The confined evaporation of laser-deposited nanoparticles enables the synthesis of large-area 2D metal chalcogenide crystals in pre-patterned locations. This approach overcomes processing roadblocks that have hindered the scalable growth and pattering of such materials for optoelectronic and energy related applications.
“Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation” (highlight slide)
M. Mahjouri-Samani et al., ACS Nano (2014) | DOI: 10.1021/nn5048124

Little Chemical Additive Makes Big Difference to Efficiency of Plastic Solar Cells
A common additive helps organize molecules during drying to self-assemble thin films for organic solar cells and improve their power-conversion efficiency. The ability to control ordering of molecules and segregation of chemical phases in solar materials may increase production of electricity from sunlight and lower solar-energy costs.
“Understanding how processing additives tune the nanoscale morphology of high efficiency  organic photovoltaic blends: From casting solution to spun-cast thin film” (highlight slide)
M. Shao et al., Advanced Functional Materials (2014) | DOI: 10.1002/adfm.201401547
Understanding Chemical and Electronic Distortions on Manganite Surfaces
Scientists mapped chemical and electronic structure at the surface of a manganite thin film and identified deviations from ideal structure. Atomic-resolution mapping will aid investigations of materials promising for energy applications, such as solid-oxide fuel cells.
“Chemically induced Jahn-Teller ordering on manganite surfaces” (highlight slide)
Z. Gai et al., Nature Communications (2014) | DOI: 10.1038/ncomms5528
Complex interplay yields a novel data-storage approach
The electrically biased tip of a scanning probe microscope was used to switch spontaneous polarization on and form complex symmetrical and asymmetrical domains in a technologically promising ferroelectric material. Manipulation of nanoscale “bits” (ferroelectric domains) that encode information in their diverse shapes and sizes may form the basis of novel data storage devices that consume less energy.
“Ionic field effect and memristive phenomena in single-point ferroelectric domain switching” (highlight slide)
A.V. Ievlev et al., Nature Communications (2014) | DOI: 10.1038/ncomms5545
Deep data analysis of conductive materials
Computer algorithms for statistical analysis separated and extracted signals of conductive behavior in a complex nanomaterial. Automated decomposition of complex signals into simpler components will allow researchers to arrive at fuller insights faster.
“Deep Data Analysis of Conductive Phenomena on Complex Oxide Interfaces: Physics from Data Mining” (highlight slide)
E. Strelcov et al., ACS Nano (2014) | DOI: 10.1021/nn502029b