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 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.
We study graphene growth on hafnia (HfO2) nanoparticles by chemical vapour deposition using optical microscopy, high resolution transmission electron microscopy and Raman spectroscopy. We find that monoclinic HfO2 nanoparticles neither reduce to a metal nor form a carbide while nucleating nanometer domain‐sized few layer graphene. Hence we regard this as an interesting non‐metallic catalyst model system with the potential to explore graphene growth directly on a (high‐k) dielectric.
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.
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.
We propose a theory of thin film photovoltaics in which one of the polycrystalline films is made of a pyroelectric material grains such as CdS. That film is shown to generate strong polarization improving the device open circuit voltage. Implications and supporting facts for the major photovoltaic types based on CdTe and CuIn(Ga)Se2 absorber layers are discussed.
An original approach is proposed to study the magnetic phase separation phenomenon. It is based on the registration of the noise‐like FMR Fine Structure (FMR FS) caused by the magnetic interparticle dipole–dipole interaction between spatially separated ferromagnetic regions. Data obtained for a La0.7Pb0.3MnO3 single crystal point to the existence of spatially separated ferromagnetic regions. It is shown that FMR FS of the La0.7Pb0.3MnO3 single crystal is temperature reversible and disappears at the maximum of magnetoresistance.
The properties of transition‐metal (V, Cr, Mn, Fe, Co, Ni) δ‐doped ZnO are reported based on ab‐initio electronic structure calculations where the on‐site electronic correlations are included using the Hubbard parameters. The calculated electronic and magnetic properties are considerably altered with respect to usual band‐structure calculations. Most of the studied systems are found to be either half‐metals or ferromagnetic/antiferromagnetic semiconductors and thus can be employed in a variety of spintronic applications as spin‐filter materials.
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.
We demonstrated important changes produced on the modulation frequency of hybrid organic–inorganic light‐emitting diodes to examine the applicability as a light source for visible optical communications. The fabricated device structure was 4,4′‐bis[N ‐(1‐napthyl)‐N ‐phenyl‐amino]biphenyl/4,4′‐(bis(9‐ethyl‐3‐carbazovinylene)‐1,1′‐biphenyl:4,4′‐bis[9‐dicarbazolyl]‐2,2′‐biphenyl/ZnS/LiF/MgAg. This device showed an improvement in the modulation frequency using ZnS instead of an organic material, tris(8‐hydroxyquinoline)aluminum. A maximum cutoff frequency of 20.6 MHz was achieved.
Heteroepitaxial growth of III‐Sb nanowires allows for the formation of various interesting complex structures and enables the combination of their remarkable properties. In this Letter, we investigate the heteroepitaxial growth of Au‐seeded InSb and GaSb nanowires using metalorganic vapor phase epitaxy. We demonstrate successful single and double axial InSb–GaSb heterostructures in both directions. The formation properties of the grown nanowires including the compositional change of the particle and the interface sharpness are further discussed. In addition, the decomposition of InSb and GaSb segments and their side facet evolution are explained.
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.
Light‐induced degradation of charge carrier lifetime was observed in indium‐doped silicon. After defect formation, an annealing step at 200 °C for 10 min deactivates the defect and the initial charge carrier lifetime is fully recovered. The observed time range of the defect kinetics is similar to the well known defect kinetics of the light‐induced degradation in boron‐doped samples. Differences between defect formation in boron‐ and indium‐doped silicon are detected and discussed. A new model based on an acceptor self‐interstitial ASi–Sii defect is proposed and established with experimental findings and existing ab‐initio simulations.
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.
Ultrafast transverse thermoelectric voltage response has been observed in c‐axis inclined epitaxial La0.5Sr0.5CoO3thin films. Voltage signals with the rise time of 7 ns have been detected under the irradiation of pulse laser with duration of 28 ns. A concept, named response rate ratio, has been proposed to evaluate the intrinsic response rate, and this ratio in La0.5Sr0.5CoO3is smaller than that in other reported materials. The low resistivity is thought to be responsible for the ultrafast response, as low resistivity induces small optical penetration depth, and response time has a monotonous increasing relationship with this depth.
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.
We present metal wrap through (MWT) silicon solar cells with passivated surfaces based on a simplified device structure. This so‐called HIP‐MWT structure (high‐performance metal wrap through) does not exhibit an emitter on the rear side and therefore simplifies processing. The confirmed peak efficiency of the fabricated solar cells with an edge length of 125 mm, screen printed contacts and solder pads is 20.2%. To our knowledge, this is the highest value reported for large‐area p‐type silicon solar cells to date.
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.
