Materials Literature
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X-ray-absorption near-edge spectroscopy (XANES or NEXAFS) has been used to obtain information on the orientation, corrugation, and cross-linking of graphitic carbon nitride planes, structural parameters that determine the mechanical properties of the material. The contribution of p electrons from carbon and nitrogen a…
We derive an approximate analytical expression for the density-of-states singularities in single-walled carbon nanotubes. Our approximation goes beyond the lowest-order, isotropic approach and yields the energy splitting for an arbitary chiral angle in metallic nanotubes. Semiconducting tubes are shown to fall into tw…
Scanning tunneling microscope spectroscopy is used to study in detail the electronic band structure of carbon nanotubes as well as to locally investigate electronic features of interesting topological sites such as nanotube ends and bends. From a large number of measurements of the tunneling density-of-states (DOS) na…
Electroluminescence (EL) spectra of nanoscale diodes formed after gate-oxide breakdown of n+-polysilicon/oxide/p+-substrate metal–oxide–semiconductor capacitors were measured in reverse and forward bias. The nanoscale diodes, called diode antifuses, are created by the formation of a small link between the n+-poly and…
In order to understand the phase stability and physical properties of artificial close-packed Cr films, we have performed electronic structure and total-energy calculations for Cr in bcc, fcc, and hcp structures based density functional theory with local-density approximation plus generalized gradient corrections. The…
For the first time, commonly unaccessible local electronic structure parameters of Fe 2+ and Fe 3+ in minerals are derived from the calculation of the pre-edge features of X-ray absorption spectra at the Fe K edge. The Ligand Field Multiplet approach is used to calculate the eigenstates of the ions and the absolute in…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTWeak Ferromagnetism in a Three-Dimensional Manganese(II) Azido Complex, [Mn(4,4'-bipy)(N3)2]n (bipy = Bipyridine)Sujin Han, Jamie L. Manson, Jinkwon Kim, and Joel S. MillerView Author Information Department of Chemistry, Kongju National University, 182 Shinkwan, Chungnam 314-70…
The structure and electronic properties of potassium-doped single-wall carbon nanotubes have been studied by conduction electron spin resonance, conductivity $(\ensuremath{\sigma}),$ and x-ray diffraction (XRD), using in situ electrochemical methods. The spin susceptibility ${\ensuremath{\chi}}_{P}$ of the K-saturated…
The potential of acetylation of plant fibers to improve the properties of composites was studied. The chemical modification of oil palm empty fruit bunch (EFB), coconut fiber (Coir), oil palm frond (OPF), jute, and flax using noncatalyzed acetic anhydride were investigated. Proof of acetylation was indicated by the in…
The sonolytic decomposition chemistry of the refractory compound 1,4-dioxane in aqueous solution has been investigated at four ultrasonic frequencies (205, 358, 618, and 1071 kHz). To maintain fully saturated solutions, argon and oxygen were used as sparge gases. Using a frequency of 358 kHz, the observed first-order…
Time-resolved photoluminescence spectroscopy at 2 K was used to measure the radiative recombination lifetime of the allowed (Γ5) and forbidden (Γ6) free excitons in ZnO. The measurements were made on a sample containing internal strain, which altered the sample symmetry, and resulted in relaxed selection rules, allowi…
The presence of silicon nanocrystals in Er doped SiO2 can enhance the effective Er optical absorption cross section by several orders of magnitude due to a strong coupling between quantum confined excitons and Er. This article studies the fundamental processes that determine the potential of Si nanocrystals as sensiti…
The low-frequency vibrational spectrum of an isolated nanometer-scale solid differs dramatically from that of a bulk crystal, causing the decay of a localized electronic state by phonon emission to be inhibited. We show, however, that an electron can also interact with the rigid translational motion of a nanocrystal.…
The current carrying capacity of ballistic electrons in carbon nanotubes that are coupled to ideal contacts is analyzed. At small applied voltages, electrons are injected only into crossing subbands, the differential conductance is ${4e}^{2}/h.$ At applied voltages larger than $\ensuremath{\Delta}{E}_{\mathrm{NC}}/2e$…
The correlation between ${}^{29}\mathrm{Si}$ chemical shifts and Si-O-Si bond angles in ${\mathrm{SiO}}_{2}$ is determined within density-functional theory for the full range of angles present in vitreous silica. This relation closely reproduces measured shifts of crystalline polymorphs. The knowledge of the correlati…
Unlike semiconducting TiCoSb, ZrCoSb and HfCoSb half-Heusler phases are semimetallic below room temperature and exhibit small Seebeck coefficients of ∼−10 μV/K at 300 K. However, upon substituting (doping) the Co and Sb sites with Pt and Sn, respectively, much larger thermopowers (S) are obtained. For ZrCoSb, S reache…
Iron nitride Fe4N is studied by full-potential LAPW method. Structure parameters, electronic and magnetic properties as well as hyperfine interaction parameters are obtained. We observe perfect agreement with experimental results. Hypothetical Fe4N structure was also calculated to study the influence of disordering ef…
Two electrons confined in quantum dots (QD's) are studied under an assumption of a Gaussian confining potential and its parabolic approximation. We have calculated the energy levels of singlet and triplet states as functions of the range and depth of the confining potential in the two-dimensional (circular) and three-…
The crystal structure of the new fast oxide-ion conductor La 2 Mo 2 O 9 (ionic conductivity of 0.06 S cm - 1 at 800 °C) has been studied. This compound presents a reversible phase transformation around 580 °C from a low-temperature form α-La 2 Mo 2 O 9 to a high-temperature form β-La 2 Mo 2 O 9 . The high-temperature…
In recent years, lack of donor organs has caused many to consider tissue engineering methods as means to replace diseased or damaged organs. This newly-emerging field uses tissue-specific cells in a three-dimensional organization, provided by a scaffolding material, to return functionality of the organ. For these appl…