Monte‐Carlo simulations predict that a local correlated disorder is responsible for many of the novel transport and magnetic properties of colossal magnetoresistance (CMR) materials such as manganites. One important prediction of these models is that the resistivity at the metal–insulator transition (MIT) in manganites depends strongly on the correlated quenched disorder. However, experimental confirmation has been challenging since it is difficult to control the amount of disorder in these compounds. We carried out experiments on Sm0.55Sr0.45MnO3, a prototypical CMR manganite with a sharp MIT, whereby the oxygen‐related disorder is systematically enhanced by low temperature thermal activation. We observe dramatic changes in the temperature dependence of resistivity at the MIT as the amount of quenched disorder is increased, occurring in a manner that is in agreement with theoretical predictions.
We report a very simple and novel approach to produce anodic TiO2 nanotube arrays with highly defined and ordered tube openings. It is based on carrying out anodization through a slowly soluble photoresist coating. This eliminates the formation of undesired initiation layers on the tube tops and protects them to a certain extent from etching by the electrolyte.
We report a stacked Y2O3/TiOx resistive random access memory (RRAM) device, showing good high‐temperature switching characteristics of extremely low reset current of 1 μA at 150 °C, large off/on resistance window (>200) at 150 °C, large rectification ratio of ～300 at 150 °C and good current distribution at 85 °C. The good rectifying property, lower high‐temperature sneak current and tighter high‐temperature current distribution can be attributed to the combined results of the oxygen vacancies in TiOx and the related carrier depletion effect.
A high‐stability Eu complex has been achieved by coating with a silica glass via a low temperature sol–gel process using deuterated methanol. A three‐dimensional glass network protects the Eu complex from free oxygen and/or water to change the ligand structure. In addition, the chemical bond of the deuterated Eu complex is more stable than that of the conventional Eu complex. Therefore, we achieved a high‐thermal‐stability Eu complex encapsulated by a sol–gel derived silica glass using deuterated methanol instead of ethanol.
In this Letter, a novel modified anodization was utilized to synthesize high‐aspect‐ratio, top‐open and ultraflat‐surface TiO2 nanotubes. The interruption of voltage during anodization leads to the formation of a double‐layered structure. Due to the weak mechanical connection between the upper and the underlying layer, the two parts can be easily detached. Compared with the conventional ultrasonication method to remove the clusters of nanotubes where rough surfaces resulted, this efficient and reliable strategy may facilitate further applications of TiO2 nanotubes in diverse conditions.
The metastability of the bixbyite‐ and corundum‐type In2O3 polymorphs up to 33 GPa (at room temperature) is shown. While compressed (in diamond anvil cells) and laser‐heated, both polymorphs undergo a phase transition to the Rh2O3‐II‐type structure (space group Pbcn, No. 60). The direct transition from bixbyite to Rh2O3‐II structure has not yet been observed for any other oxide.
Lead carbonate chloride, Pb2CO3Cl2, known as mineral phosgenite, is introduced as a novel SRS‐active carbonate crystal with tetragonal symmetry. Under picosecond one‐micron laser pumping Raman‐induced χ(3)‐nonlinear generation in the near‐IR is observed. All recorded high‐order Stokes and anti‐Stokes sidebands are identified and attributed to two SRS‐promoting vibration modes with ωSRS1 ≈ 1062 cm–1 and ωSRS2 ≈ 86 cm–1.
ZnO thin films with a rippled surface structure were used as electron‐collecting layers of inverted organic photovoltaics (OPVs). Using additional ultrathin layers of ZnO and TiO2 fabricated using atomic layer deposition (ALD), not only the power‐conversion efficiency of the OPVs could be increased (up to 3.5%), but also the photovoltaic performance became nearly constant within 100 days without any additional encapsulations of the solar cells under ambient conditions.
Alkali‐free Cu(In,Ga)Se2(CIGS) absorbers grown on Mo‐coated alumina (Al2O3) substrates were doped with potassium (K) after CIGS growth by a potassium fluoride (KF) post‐deposition treatment (PDT). The addition of K to the absorber leads to a strong increase in cell efficiency from 10.0% for the K‐free cell to 14.2% for the K‐doped cell, mainly driven by an increase in the open‐circuit voltage Voc and the fill factor FF, and to an increase in the net charge carrier density. Hence K doping by KF‐PDT is comparable to doping with Na.
The Fe3O4(111)/graphene/Ni(111) trilayer is proposed to be used as an ideal spin‐filtering sandwich where the half‐metallic properties of magnetite are used. Thin magnetite layers on graphene/Ni(111) were prepared via successive oxidation of a thin iron layer predeposited on graphene/Ni(111) and the formed system was investigated by means of low‐energy electron diffraction and photoelectron spectroscopy. The electronic structure and structural quality of the graphene film sandwiched between two ferromagnetic layers remain unchanged upon magnetite formation as confirmed by experimental data.
In this Letter, we report a low operation voltage and high mobility flexible InGaZnO thin‐film transistor (TFT) using room‐temperature processed Y2O3/TiO2/Y2O3 gate dielectric. The flexible IGZO TFT showed a low threshold voltage of 0.75 V, a small sub‐threshold swing of 137 mV/decade, a good field effect mobility of 32.7 cm2/V s, and a large Ion/Ioff ratio of 1.7 × 106. The low operation voltage, small sub‐threshold swing and high mobility could be ascribed to the combination of high‐κ TiO2 and large band gap Y2O3, which provide the potential to meet the requirements of low‐temperature and low‐power portable electronics.
We present a computational study based on time‐dependent density functional theory of the optical absorption spectra of TiO2 nanowires sensitized with organic dye molecules. We concentrate on catechol and squaraine dyes. For those molecules, we compute adsorption geometries and energies and investigate the optical properties of the combined dye– nanowire system. We find that although the molecules have qualitatively different optical spectra in the gas phase, both lead to an enhancement of the absorption in the visible frequency range when adsorbed on a nanowire.
A facile metal catalyst free route to synthesize boron doped (0.6%–1.0%) carbon nanotubes via ceramic nanowires in which the formation of the nanowires (probably serving as templates), the carbon nanotubes and their doping all occur unanimously in the reaction, is presented.
Ordered Sr2CrReO6 has been synthesized recently. It is measured to be ferrimagnetic semiconductor, in contrary to the previous reports of metallic properties. To solve the discrepancy, we have investigated the compound by using the density functional theory. The semiconducting behavior is reproduced by including the electron correlation and spin–orbit coupling simultaneously. The calculated band gap is 0.22 eV, close to the experimental value of 0.21 eV. A large orbital moment of 0.69µB is found for Re, which is caused by the Coulomb‐enhanced spin–orbit coupling. By applying pressure, a semiconductor to half‐metal transition is observed through 5% volume compression.
Optically transparent and high‐quality hybrid ZnO nanoparticle and anthracene embedded polyphenylsiloxane (PPS) glass films were spin‐coated on quartz substrates. A strong Förster resonant energy transfer (FRET) process was indicated by the observation of quenching of the ZnO emission and an enhancement of the anthracene emission at room temperature. The efficiency of this energy transfer between ZnO and the S1 vibronic states of the anthracene molecules can be optimized to exceed 90%.
Polymer nanocomposites containing different concentrations of Au nanoparticles have been investigated by small angle X‐ray scattering and electronic absorption spectroscopy. The variation in the surface plasmon resonance (SPR) band of Au nanoparticles with concentration is described by a scaling law. The variation in the plasmon band of ReO3 nanoparticles embedded in polymers also follows a similar scaling law.
In this study, we report a low power Ni/GeOx /TiOy /TaN resistive random access memory (RRAM) using plasma‐modified electrode. The low sub‐mA switching current, highly uniform switching cycles (only 4% variation for the set) and good high‐temperature current distribution at 125 °C are simultaneously achieved in this RRAM device. Such good performance can be ascribed to interface plasma treatment on TaN electrode where the resulting Ta–N ionic bond increases the oxidation resistance and reduces the oxygen vacancy concentration near TaN interface that is favorable to lower switching power and improve high‐temperature current distribution.
In this Letter, we report on a new nanofabrication technology to yield highly arrayed nanoelectrodes for organic–inorganic solar cells that promise new levels of performance and efficiency. This technology efficiently controls the effective area of highly arrayed nanoelectrodes and allows for the maximum incorporation of organic materials within the voids. Particularly the 3D parameters such as thickness, spacing, and height of the nanostructures are controlled non‐lithographically by atomic layer deposition technology.
MgZnO‐based ultraviolet avalanche photodetectors (APDs) have been fabricated from Au/MgO/Mg0.44Zn0.56O/MgO/Au Schottky structures. The carrier avalanche multiplication is realized via an impact ionization process occurring in the MgO layer under relatively large electric field. The APDs exhibit an avalanche gain of 587 at 31 V bias, and the response speed of the APDs is in the order of microseconds.
