Materials Literature
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The room-temperature ferromagnetism of Zn 1− x Al x O nanoparticles synthesized by a sol−gel method is reported in this paper. X-ray diffraction and selected area electron diffraction results show that the Al atoms have successfully substituted for some of the Zn atoms in the ZnO lattice without forming other new phas…
In this short paper, the authors report a new computational approach in the context of Density Functional Theory (DFT). It is shown how it is possible to speed up the self-consistent cycle (iteration) characterizing one of the most well-known DFT implementations: FLAPW. Generating the Hamiltonian and overlap matrices…
In percolating networks of mixed metallic and semiconducting carbon nanotubes (CNTs), there is a tradeoff between high on-current (dense networks) and high on/off ratio (sparse networks). Experiments on transistors and Monte Carlo simulations were performed to determine the scaling behavior of device resistivity as a…
We report a theoretical study of the quasiparticle lifetime and the quasiparticle mean free path caused by inelastic electron-electron scattering in ferromagnetic compounds of the Co-Fe and Ni-Fe systems. The study is based on spin-polarized calculations, which are performed within the $GW$ approximation for equiatomi…
We report room temperature scanning tunneling microscopy and spectroscopy study of bilayer graphene prepared by mechanical exfoliation on SiO$_2$/Si surface and electrically contacted with gold pads using a mechanical mask. The bulk conductivity shows contribution from regions of varying electron density indicating si…
Say cheeeese! The thixotropic processes that occur in a naphthalenediimide-based organogel can be imaged in real time by TEM and AFM (see picture). The self-assembled 1D fibers disintegrate under mechanical stress and undergo a self-healing process during a resting time to reconstitute the 1D fibers.
We present characteristics of dual-gated graphene devices with an Al2O3 gate dielectric formed by an O3-based atomic-layer-deposition process. Raman spectra reveal that a O3 process at 25°C on single-layered graphene introduces the least amount defects, while a substantial number of defects appear at 200 °C. This grap…
Peptide Self-Assembly for Lithium Ion Batteries: Nanostructures of transition metal phosphates were fabricated through biomimetic mineralization of self-assembled peptide hydrogel nanofibers. FePO4-mineralized peptide nanofibers were readily converted to carbon-coated FePO4 nanotubes after heat treatment and exhibited…
We report resistance switching effects in polycrystalline pure BiFeO3 films prepared by a sol-gel method. By current-voltage and conductive atomic force microscope (c-AFM) measurements, resistance switching effects are observed in BiFeO3 films annealed at and above 650 °C. A fresh sample can be transformed into a low-…
We have investigated antidot lattices, which were prepared on exfoliated graphene single layers via electron-beam lithography and ion etching, by means of scanning Raman spectroscopy. The peak positions, peak widths, and intensities of the characteristic phonon modes of the carbon lattice have been studied systematica…
The transition metal nitride BaHfN$_2$, which consists of weakly bonded neutral slabs of closed shell ions, has structural and chemical similarities to other layered nitrides which have impressive superconducting T$_c$ when electron doped: A$_x$HfNCl, A$_x$ZrNCl, A$_x$TiNCl, with $T_c= 25.5$, $15.2$ and $16.5$ K, resp…
Using Green-function many-body theory, we present the details of a formally exact adiabatic-connection fluctuation-dissipation density-functional theory based on range separation, which was sketched in Toulouse, Gerber, Jansen, Savin and Angyan, Phys. Rev. Lett. 102, 096404 (2009). Range-separated density-functional t…
Structure transformation by heat treatment in single-walled carbon nanotubes (SWCNT) is investigated using molecular dynamics simulation. The critical temperature for the collapse of pure SWCNT is as high as 4655 K due to strong covalent carbon-carbon bonding. Above 2000 K, the cross section of SWCNT changes from circ…
Understanding the behavior of molecular systems under pressure is a fundamental problem in condensed matter physics. In the case of nitrogen, the determination of the phase diagram and in particular of the melting line, are largely open problems. Two independent experiments have reported the presence of a maximum in t…
The phonon localized edge modes are systematically studied, and two conditions are proposed for the existence of the localized edge modes: (I) coupling between different directions ($x$, $y$ or $z$) in the interaction; (II) different boundary conditions in three directions. The generality of these two conditions is il…
Nanostructured carbonaceous materials, that is, carbon materials with a feature size on the nanometer scale and, in some cases, functionalized surfaces, already play an important role in a wide range of emerging fields, such as the search for novel energy sources, efficient energy storage, sustainable chemical technol…
Dendrimer synthesis should not be tedious and time-consuming. By utilizing an AB 2 −CD 2 approach and having orthogonal, “clickable” groups on each monomer, the time for dendrimer assembly can be drastically reduced. This was shown by preparation of a sixth generation dendrimer from starting monomer units in a single…
A tight-binding analytic framework is combined with first-principles calculations to reveal the mechanism underlying the strain effects on electronic structures of graphene and graphene nanoribbons (GNRs). It provides a unified and precise formulation of the strain effects under various circumstances-including the shi…
Microscopic, structural, transport, and thermodynamic measurements of single crystalline $\text{Ba}{({\text{Fe}}_{1\ensuremath{-}x}{\text{TM}}_{x})}_{2}{\text{As}}_{2}$ ($\text{TM}=\text{Ni}$ and Cu) series, as well as two mixed $\text{TM}=\text{Cu}/\text{Co}$ series, are reported. In addition, high-magnetic field, an…
We propose a simple, yet highly efficient and robust device for producing valley polarized current in graphene. The device comprises of two distinct components; a region of uniform uniaxial strain, adjacent to an out-of-plane magnetic barrier configuration formed by patterned ferromagnetic stripes. We show that when t…