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.
The multiferroic Pb(Fe1/2V1/2)O3 (PFV) bulk ceramic was fabricated by a conventional ceramic sintering method. The strong visible‐light photovoltaic effect in Sn‐doped‐In2O3(ITO)/PFV/ITO structure capacitor was observed. The open‐circuit voltage was up to ～0.7 V, which was much higher than the value (～0.3 V) in BiFeO3 film. The photo‐excited electric current is almost proportional to the incident light illumination intensity. The good visible‐light photovoltaic makes PFV ceramic a potential candidate for practical application in solar cell devices.
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.
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 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 the present work we use a series of Ti–Ru alloys, with minor amounts of Ru (0.01, 0.02, 0.05 and 0.2 at%) to grow anodic self‐organized Ru‐doped TiO2 nanotube layers. When used in dye‐sensitized solar cells (DSSCs), the nanotube layers with an optimum amount of Ru (0.02 at% Ru in the alloy) show a considerable increase in solar cell efficiency (η = 5.2%) under AM1.5 (100 mW/cm2) conditions compared with non‐doped TiO2 nanotubes (η = 4.3%).
Osmium diboride has been known for some time as a low compressibility material and a superhard material. It is suitable for hard coating applications. It is also a superconductor below 2.1 K. Using first‐principles calculations, the author investigated the geometry of its Fermi surface (FS) and calculated the related physical quantities. The theoretical results are used to predict the frequencies of the Shubnikov–de Haas quantum oscillations. Comparison with recent measurements of the magneto‐resistance oscillations in osmium diboride is made.
We prepared and investigated grain boundary Josephson junctions based on SrTiO3 bicrystal substrates. During the deposition of YBa2Cu3O7–δ (YBCO) gold nanocrystals forming from an intermediate gold layer can modify the crystalline structure and thus the properties of the YBCO grain boundaries. The variation of the film thickness of the Au seed layer changes the growth conditions of the YBCO film and the Au nanocrystals. The values of the characteristic ICRN product do not change whereas the values of the critical current IC decrease.
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.
Organic field‐effect transistors (OFETs) based on interconnected nanowire networks of P3HT have been successfully fabricated by using a mixed‐solvent method. The nanowire network density can be tuned by controlling the anisole/chlorobenzene ratio of mixed solvents. The obtained field‐effect mobility, threshold voltage and the ratio of on‐state current and off‐state current (Ion/Ioff) was 0.0435 cm2/V s, –10 V and 1.75 × 104, respectively. The three‐dimensional and interconnected nanowire structure of the networks can enhance the charge transport in P3HT.
The two‐dimensional layered semiconducting di‐chalcogenides are emerging as promising candidates for post‐Si‐CMOS applications owing to their excellent electrostatic integrity and the presence of a finite energy bandgap, unlike graphene. However, in order to unravel the ultimate potential of these materials, one needs to investigate different aspects of carrier transport. In this Letter, we present the first comprehensive experimental study on the dependence of carrier mobility on the layer thickness of back‐gated multilayer MoS2 field‐effect transistors. We observe a non‐monotonic trend in the extracted effective field‐effect mobility with layer thickness which is of relevance for the design of high‐performance devices. We also discuss a detailed theoretical model based on Thomas–Fermi charge screening and interlayer coupling in order to explain our experimental observations. Our model is generic and, therefore, is believed to be applicable to any two‐dimensional layered system.
Heteroepitaxial growth of kesterite Cu2ZnSnS4 (CZTS) thin film on cubic ZnS(100) single crystal substrate was achieved by radio frequency magnetron sputtering from a single CZTS target. An optimal substrate temperature in the range of 470–500 °C is found suitable for this epitaxial growth. The growth of CZTS was confirmed to be along a‐axis. The sputtered CZTS thin film is homogeneous throughout the whole film. The band gap of the film is found to be approximately 1.51 eV, i.e., promising for high efficiency thin film solar cells.
Bulk polycrystalline La0.8Li0.2MnO3 is found to switch between a low‐resistance state and a high‐resistance state on thermal cycling. The low‐temperature, high‐resistance state exhibits strong electroresistance whereas the high‐temperature, low‐resistance state does not. The change in resistance between the two distinct states is of two orders of magnitude. It is proposed that the observed metastability may serve as the basis for resistive thermal‐switching devices.
The authors describe an organic complementary inverter with N,N′‐ditridecyl‐3,4,9,10‐perylenetetracarboxylic diimide as an n‐type semiconductor and pentacene as a p‐type semiconductor. Each transistor of the inverter exhibited high carrier mobility: 1.62 cm2/Vs for an n‐type drive transistor and 0.57 cm2/Vs for a p‐type switch transistor. The gain of the inverter reached 125. Another inverter using Ta2O5 as a high κ gate dielectric performed well with a gain of 500 and an operation voltage of only 5 V.
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.
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 the fabrication procedure and the characterization of an Al0.3Ga0.7As solar cell containing high‐density GaAs strain‐free quantum dots grown by droplet epitaxy. The production of photocurrent when two sub‐bandgap energy photons are absorbed simultaneously is demonstrated. The high quality of the quantum dot/barrier pair, allowed by the high quality of nanostructured strain‐free materials, opens new opportunities for quantum dot based solar cells.
