The current–voltage characteristics and photoresponse of mesa structured {111}‐oriented homoepitaxial CVD diamond p(i)n‐junctions with different intrinsic layer thickness are investigated. When a sufficiently thick intrinsic layer is present, a rectification ratio of 108 at ±10 V could be obtained. Good rectifying diodes show a high photoresponse ratio between 210 nm (above bandgap) and 500 nm (below bandgap), making them suitable for UV detection purposes. The results are compared with similar measurements carried out on polycrystalline CVD diamond pn‐junctions.
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.
Graphene, the two‐dimensional form of carbon presents outstanding electronic and transport properties. This gives hope for the development of applications in nanoelectronics. However, for industrial purpose, graphene has to be supported by a substrate. We focus here on the graphene‐on‐SiC system to discuss how the SiC substrate interacts with the graphene layer and to show the effect of the interface on graphene atomic and electronic structures.
Write‐once–read‐many‐times memory (WORM) devices were fabricated using Ti/Au and Au as top contacts on ZnO thin films on Si. Electrical characterization shows that both types of WORM devices have large resistance OFF/ON ratio (R ratio), small resistance distribution range, long retention and good endurance. WORM devices with Au top contact have better performance of higher R ratio because of a larger work function of Au compared to Ti.
Nanostructures formed in a titanium dioxide (TiO2)–poly(styrene)‐block‐poly(ethyleneoxide) nanocomposite film on top of fluor‐doped tin oxide (FTO) layers are investigated. The combinatorial approach is based on probing a wedge‐shaped FTO‐gradient with grazing incidence small angle X‐ray scattering (GISAXS) in combination with a moderate micro‐focus X‐ray beam. The characteristic lateral length is given by adjacent nanowire‐shaped TiO2 regions. It decreases from 200 nm on the thick FTO layer to 90 nm on the bare glass surface.
We report on solution‐processible polymer solar cells (PSCs) fabricated on a papery substrate using carton. Highly conductive PEDOT:PSS was used as a bottom anode and planarization layer, and a semi‐transparent top cathode was applied. This research could be an important approach to the development of all‐solution‐processible papery PSCs as well as paper electronics.
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 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.
We have demonstrated an effective method of enhancing the power efficiency of double–emissive solution‐processed blue phosphorescent organic light‐emitting diode (PHOLED) by controlling the charge transport in the heterojunction and emissive layer. The first emissive layer consists of poly(vinylcarbazole) (PVK) and bis(4,6 difluorophenylpyridinato‐N,C2)picolinatoiridium (FIrpic) mixed with 4,4′,4″‐tris(N‐carbazolyl)‐triphenylamine (TCTA) or 1,3‐bis[(4‐tert‐ butylphenyl)‐1,3,4 oxidiazolyl] phenylene (OXD‐7). The second layer consists of an alcohol‐soluble 2,7‐bis(diphenylphosphoryl)‐9,9′‐spirobi[fluorene] (SPPO13) and FIrpic blend. The incorporation of OXD‐7 into PVK blurs the interface between the emissive layers and widens the recombination zone while blending TCTA into PVK reduces the hole‐ injection barrier from PEDOT:PSS to PVK. By adding TCTA or OXD‐7 into the first emissive layer, we have achieved a power efficiency of 10 lm/W and 11 lm/W, respectively, at 1000 cd/m2.
Steady‐state and time‐resolved photoluminescence of silicon nanoparticles dispersed in low‐polar liquids at above room temperature is studied. The roles of low‐polar liquids as well as mechanisms responsible for their temperature‐dependent photoluminescence are discussed. The thermal sensitivity of the photoluminescence is estimated and application of the nanoparticles as nanothermometers is proposed.
The crystallization process of mechanically alloyed Fe75Zr25 metallic glasses is investigated by means of both thermo‐magnetization and in situ neutron powder thermo‐diffraction experiments in the temperature range 300–1073 K. It was found that the crystallization takes place in a two‐step process, involving firstly the appearance of metastable Fe and Fe2Zr crystalline phases between 880 K and 980 K, and a subsequent polymorphic transformation into Fe3Zr above 980 K. These findings explain the anomalous magnetization vs. temperature behaviour on heating–cooling cycles.
Dip‐coating of a colloidal suspension is investigated in situ with microbeam grazing incidence small‐angle X‐ray scattering. We focus on the real‐time monitoring of a vertical dip‐coating process yielding insights into structural changes during pattern formation of the thin film. With the selected configuration a fixed spot on the sample surface is probed and the structural information at the time the contact line passes this spot is obtained, hence revealing the structure at the vicinity of the flowing meniscus owing to the microfocused beam. After dip‐coating the morphology is analyzed with atomic force microscopy, yielding real space information about the arrangement of individual nanoparticles at the film surface.
We demonstrate the monolithic integration of a microstructured organic photodiode with a planar optical stripe waveguide. The manufacturing of this waveguide‐integrated organic photodiode is based on an UV photolithography process. The integration of photodiodes with optical waveguides represents an essential building block in the field of optoelectronic‐photonic integrated circuits.
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.
Epitaxial TiC/SiC multilayers were grown by magnetron sputtering at a substrate temperature of 550 °C, where SiC is normally amorphous. The epitaxial TiC template induced growth of cubic SiC up to a thickness of ～2 nm. Thicker SiC layers result in a direct transition to growth of the metastable amorphous SiC followed by renucleation of nanocrystalline TiC layers.
Persistent layer‐by‐layer growth is demonstrated for pulsed‐laser homoepitaxy of ZnO thin films on $(000\bar 1)$ ZnO single crystals. Employing interval pulsed‐laser deposition (PLD), RHEED oscillations are stabilized over a film thickness of about 90 nm. For interval pulsed laser deposited films a considerably decreased root‐mean‐square surface roughness of 0.26 nm was found, in comparison to 0.74 nm for conventional PLD. A small asymmetry in the X‐ray diffraction (XRD) 2θ –ω scan reveals compressive strain in the thin film being slightly larger for interval PLD as compared to conventional PLD. The FWHM of the photoluminescence (PL) I6 line is higher with about 500 µeV as compared to 350 µeV for the conventional PLD. Consequently, both XRD as well as PL indicate a slightly higher amount of charged defects for the interval PLD.
