Mg doping of thermochromic VO 2 films enhances the optical transmittance and decreases the metal-insulator transition temperature

Using photoelectron spectroscopy, we investigate the band alignments of the Cu2O/ZnO heterointerface and compare the findings with the corresponding values for Cu2O/GaN. While for Cu2O/ZnO, we find a valence band offset (VBO) of 2.17 eV and a conduction band offset (CBO) of 0.97 eV, both values are considerably reduced for Cu2O/GaN where the numbers are 1.47 eV (VBO) and 0.24 eV (CBO), respectively. The large CBO between ZnO and Cu2O will very likely result in low photovoltaic power conversion efficiencies as is the current status of Cu2O/ZnO solar cells.

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The dynamic properties of water in the hydration shell of hemoglobin have been studied by means of dielectric permittivity measurements and nuclear magnetic resonance spectroscopy. The temperature behavior of the complex permittivity of hemoglobin solutions has been measured at 3.02, 3.98, 8.59, and 10.80 GHz. At a temperature of 298 K the average rotational correlation time tau of water within a hydration shell of 0.5-nm thickness is determined from the activation parameters to be 68 +/- 10 ps, which is 8-fold the corresponding value of bulk water. Solvent proton magnetic relaxation induced by electron-nuclear dipole interaction between hemoglobin bound nitroxide spin labels and water protons is used to determine the translational diffusion coefficient D(T) of the hydration water. The temperature dependent relaxation behavior for Lamor frequencies between 3 and 90 MHz yields an average value D(298K) = (5 +/- 2) x 10(-10)m2 s-1, which is about one-fifth of the corresponding value of bulk water. The decrease of the water mobility in the hydration shell compared to the bulk is mainly due to an enhanced activation enthalpy.

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The influence of nitrogen incorporation in high concentrations on the structural properties and morphology of SnO2–xNx thin films grown by chemical vapor deposition is studied. A decrease in crystallite size and a lattice expansion in SnO2–xNx films with increasing x are found by X‐ray diffraction analysis and Raman spectroscopy. Substitutional nitrogen with a binding energy of 397.15 eV was detected by X‐ray photoelectron spectroscopy, attributed to the N3− ion in the SnN bond. The increase of the N atomic concentration x in SnO2–xNx films from 0 to 7.9 at.% without phase separation with increasing NH3 flow rate during the deposition is accompanied by a decrease of O atomic concentration.

Thin films of nitrogen‐doped cuprous oxide (Cu2O:N) have been deposited by means of direct‐current and radio‐frequency sputtering using a metallic copper target and a mixture of argon, oxygen, and nitrogen for generating the plasma. The doping with nitrogen appears to significantly increase the electrical conductivity of the films. All samples exhibit a temperature‐activated transport behavior. It is shown that the activation energy decreases proportionally to the reciprocal distance between nitrogen atoms, which indicates that a constant fraction of nitrogen is most likely substitutionally incorporated on oxygen site in the Cu2O lattice and acts as an acceptor. Nevertheless, Raman measurements suggest that molecular nitrogen can also be found in the samples, bound at different sites inside the bulk and at the surface.

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