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Semiconductors with electrically tunable band gaps are of great interest in controlling transparency to electromagnetic radiation. Thin films of perovskite nickelate NdNiO3 (NNO), a class of correl...

Ultrasound-assisted surface modification of graphene nanoplatelets (GNPs) has made possible for in situ growth of V2O5 nanoparticles; homogeneously decorating inter-connected two-dimensional GNPs. The as-fabricated One-Step V2O5|GNPs nanocomposite exhibited enhanced electronic conductivity and facilitates higher Li+ ion insertion/ extraction kinetics, attained the high capacity of 297 mA h g−1 (10 mA g−1) corresponding to ∼2 Li+ ion insertion/ extraction. Consequently, the sonochemically tailored One-Step V2O5|GNPs nanocomposite delivered the specific capacity of 248 mA h g−1 at 50 mA g−1 with 83% capacity retention and 98.4% coulombic efficiency for the cycling studies. In addition, the rate capability studies were extended to One-Step V2O5|GNPs cathode at different current density from 10 to 200 mA g-1. On the other hand, the Two-Step (sonochemical synthesis of 200 nm V2O5 particles followed by its deposition on GNPs) V2O5|GNPs composite cathode yielded less specific capacity of 225 mA h g−1 (10 mA g-1) than the One-Step V2O5|GNPs nanocomposite cathode.

Tunable plasmonic structure at the nanometer scale presents enormous opportunities for various photonic devices. In this work, we present a hybrid plasmonic thin film platform: i.e., a vertically aligned Au nanopillar array grown inside a TiN matrix with controllable Au pillar density. Compared to single phase plasmonic materials, the presented tunable hybrid nanostructures attain optical flexibility including gradual tuning and anisotropic behavior of the complex dielectric function, resonant peak shifting and change of surface plasmon resonances (SPRs) in the UV-visible range, all confirmed by numerical simulations. The tailorable hybrid platform also demonstrates enhanced surface plasmon Raman response for Fourier-transform infrared spectroscopy (FTIR) and photoluminescence (PL) measurements, and presents great potentials as designable hybrid platforms for tunable optical-based chemical sensing applications.

Solid-state ion shuttles are of broad interest in electrochemical devices, nonvolatile memory, neuromorphic computing, and biomimicry utilizing synthetic membranes. Traditional design approaches are primarily based on substitutional doping of dissimilar valent cations in a solid lattice, which has inherent limits on dopant concentration and thereby ionic conductivity. Here, we demonstrate perovskite nickelates as Li-ion shuttles with simultaneous suppression of electronic transport via Mott transition. Electrochemically lithiated SmNiO 3 (Li-SNO) contains a large amount of mobile Li + located in interstitial sites of the perovskite approaching one dopant ion per unit cell. A significant lattice expansion associated with interstitial doping allows for fast Li + conduction with reduced activation energy. We further present a generalization of this approach with results on other rare-earth perovskite nickelates as well as dopants such as Na + . The results highlight the potential of quantum materials and emergent physics in design of ion conductors.

Fast-ion conductors are of broad interest in diverse fields such as electrochemical energy and non-volatile memory technologies. In this study, δ -phase Bi 2 O 3 thin film was stabilized to room temperature via reactive magnetron sputter deposition and characterized by X-ray diffraction and Raman spectroscopy. The δ -phase Bi 2 O 3 thin films were highly textured along ( 1 1 1 ) direction on various substrates and stable during annealing up to 400 °C in air and 200 °C in 5% H2 atmosphere. Electrochemical impedance measurements on δ -phase Bi 2 O 3 thin films show an ionic conductivity of 0.001 S/cm at 400 °C and an activation energy of 0.98 eV. δ -phase Bi 2 O 3 thin films based resistance switching cells (Ag/ δ - Bi 2 O 3 /Pt or Ag/ δ - Bi 2 O 3 /Au) show unipolar resistance switching phenomena. The voltage difference between the RESET and SET voltage is over 0.8 V and the resistance contrast between high resistance state (HRS) and low resistance state (LRS) is greater than 10 3 . The resistance switching parameters, like FORMING voltage, SET voltage and RESET voltage can be controlled by the thickness of δ - Bi 2 O 3 . In the low resistance state, both the absence of superconductivity down to 2 K and magnetoresistance value indicates metallicity originates from non-stoichiometric bismuth oxide and not pure bismuth metal. The electric field required for SET and RESET operations are estimated to be 7 MV/m and 3.25 MV/m respectively.

A meticulous solid state chemistry approach has been developed for the synthesis of carbon anode from a sustainable source. The reaction mechanism of carbon formation during pyrolysis of sustainable feed-stock was studied in situ by employing Raman microspectroscopy. No Raman spectral changes observed below 160 °C (thermally stable precursor) followed by color change, however above 280 °C characteristic D and G bands of graphitic carbon are recorded. Derived carbon particles exhibited high specific surface area with low structural ordering (active carbons) to low specific surface area with high graphitic ordering as a function of increasing reaction temperature. Carbons synthesized at 600 °C demonstrated enhanced reversible lithiation capacity (390 mAh g−1), high charge-discharge rate capability, and stable cycle life. On the contrary, carbons synthesized at higher temperatures (>1200 °C) produced more graphite-like structure yielding longer specific capacity retention with lower reversible capacity.

Sodium-ion batteries are emerging as an alternative energy storage system for lithium-ion batteries because of the abundance and low cost of sodium. Various carbon-based anode materials have been investigated in order to improve sodium battery performance and cycle life. In this study, because of its abundance and high porosity, pistachio shell was selected as the primary carbon source, and carbonization temperatures ranged from 700 to 1500 °C. Pistachio shell carbonized at 1000 °C resulted in a highly amorphous structure with specific surface area 760.9 m2 g–1 and stable cycle performance (225 mA h g–1 at 10 mA g–1). Our initial results obtained from carbonized pistachio shell suggest that sufficient electrochemical performance may be obtained from biowaste materials, offering new pathways for sustainable electro-mobility and other battery applications.

Bulk metals and metal chalcogenides are found to dissolve in primary amine-dithiol solvent mixtures at ambient conditions. Thin-films of CuS, SnS, ZnS, Cu2Sn(S(x),Se(1-x))3, and Cu2ZnSn(S(x)Se(1-x))4 (0 ≤ x ≤ 1) were deposited using the as-dissolved solutions. Cu2ZnSn(S(x)Se(1-x))4 solar cells with efficiencies of 6.84% and 7.02% under AM1.5 illumination were fabricated from two example solution precursors, respectively.

Semiconductor nanowires (SCNWs) provide a unique tunability of electro-optical property than their bulk counterparts (e.g., polycrystalline thin films) due to size effects. Nanoscale straining of SCNWs is desirable to enable new ways to tune the properties of SCNWs, such as electronic transport, band structure, and quantum properties. However, there are two bottlenecks to prevent the real applications of straining engineering of SCNWs: strainability and scalability. Unlike metallic nanowires which are highly flexible and mechanically robust for parallel shaping, SCNWs are brittle in nature and could easily break at strains slightly higher than their elastic limits. In addition, the ability to generate nanoshaping in large scale is limited with the current technologies, such as the straining of nanowires with sophisticated manipulators, nanocombing NWs with U-shaped trenches, or buckling NWs with prestretched elastic substrates, which are incompatible with semiconductor technology. Here we present a top-down fabrication methodology to achieve large scale nanoshaping of SCNWs in parallel with tunable elastic strains. This method utilizes nanosecond pulsed laser to generate shock pressure and conformably deform the SCNWs onto 3D-nanostructured silicon substrates in a scalable and ultrafast manner. A polymer dielectric nanolayer is integrated in the process for cushioning the high strain-rate deformation, suppressing the generation of dislocations or cracks, and providing self-preserving mechanism for elastic strain storage in SCNWs. The elastic strain limits have been studied as functions of laser intensity, dimensions of nanowires, and the geometry of nanomolds. As a result of 3D straining, the inhomogeneous elastic strains in GeNWs result in notable Raman peak shifts and broadening, which bring more tunability of the electrical-optical property in SCNWs than traditional strain engineering. We have achieved the first 3D nanostraining enhanced germanium field-effect transistors from GeNWs. Due to laser shock induced straining effect, a more than 2-fold hole mobility enhancement and a 120% transconductance enhancement are obtained from the fabricated back-gated field effect transistors. The presented nanoshaping of SCNWs provide new ways to manipulate nanomaterials with tunable electrical-optical properties and open up many opportunities for nanoelectronics, the nanoelectrical-mechanical system, and quantum devices.

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