Herein, the characterization of n‐doped InGaP:Si shells in coaxial not‐intentionally doped (nid)‐GaAs/n‐InGaP as well as n–p–n core–multishell nanowires grown by metalorganic vapor‐phase epitaxy is reported. The multi‐tip scanning tunneling microscopy technique is used for contact‐independent resistance profiling along the tapered nid‐GaAs/n‐InGaP core–shell nanowires to estimate the established emitter shell doping concentration to ND ≈ 3 · 1018 cm−3. Contacts on these shells are demonstrated and exhibit ohmic current–voltage characteristics after annealing. Application potential is demonstrated by the growth and processing of coaxial p‐GaAs/n‐InGaP junctions in n–p–n core–multishell nanowires, with n‐InGaP being the electron‐supplying emitter material. Current–voltage characteristics and temperature‐dependent electroluminescence measurements substantiate successful doping of the n‐InGaP shell. A tunneling‐assisted contribution to the leakage currents of the investigated p–n junctions is verified by the sub‐bandgap luminescence at low temperatures and is attributed to radiative tunneling processes.

Herein, a detailed analysis of leakage mechanisms in epitaxially grown nanowire heterojunction bipolar transistors (NW‐HBTs) is presented. Coaxial npn‐GaAs/InGaP core–multishell nanowires are grown via gold‐catalyzed metalorganic vapor phase epitaxy, processed to three terminal devices and electrically characterized. The key for successful NW‐HBT device functionality is the identification of tunneling as the dominant leakage mechanism in highly doped nanowire pn‐junctions. The suppression of forward tunneling currents by adjustment of the tunneling barrier width reduces the junction leakage current density into the nA cm−2 regime, which is further verified by tunneling‐related electroluminescence measurements. In addition, the suppressed tunneling accordingly increases the number of electrons that are injected from the n‐emitter into the p‐base. The latter effect influences the performance of pn‐junction based devices and is found to enable bipolar transistor functionality. Measured common emitter Gummel plots of the NW‐HBT exhibit a current gain of up to 9 and the transistor function is additionally verified by current‐controlled output characteristics.

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The polarization of photoluminescence emitted from anisotropic nanocrystals directly reflects the symmetry of the eigenstates involved in the recombination process and can thus be considered as a characteristic feature of a nanocrystal. We performed polarization resolved magneto-photoluminescence spectroscopy on single colloidal Mn 2+ :CdSe/CdS core− shell quantum dots of wurtzite crystal symmetry. At zero magnetic field, a distinct linear polarization pattern is observed, while applying a magnetic field enforces circularly polarized emission with a characteristic saturation value below 100%. These polarization features are shown to act as a specific fingerprint of each individual nanocrystal. A model considering the orientation of the crystal c⃗ axis with respect to the optical axis and the magnetic field and taking into account the impact of magnetic doping is introduced and quantitatively explains our findings. We demonstrate that a careful analysis of the polarization state of single nanocrystal emission using the full set of Stokes parameters allows for identification of the complete three-dimensional orientation of the crystal anisotropy axis of an individual nanoobject in lab coordinates.

Between 1987 and 1991 the spine was stabilised in 205 patients using corundum ceramic implants. The radiological results were assessed with a follow up of from 6 to 24 months and were graded as good in 81%. Poor results were not due to the implanted material, but were usually caused by failure to obtain full correction of the deformity at operation. Porous ceramic implants produce better radiological results, with a decrease in operating time and a reduced risk of infection.