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The electrical conductivity of hafnium (Hf)-doped YBa₂Cu₃O${}_{7-\delta }$ ceramics is investigated. Hf doping has been revealed to lead to an increase of the number of effective scattering centers for the normal charge carriers. In a broad temperature range, the excess conductivity of the investigated samples obeys an exponential temperature dependence, while near $T_c$ it is satisfactorily described by the Aslamazov–Larkin model. Meanwhile, Hf doping has been shown to lead to a notable broadening of the temperature range for the manifestation of the pseudogap anomaly in the $ab$-plane.

The growth and stability of hafnium films on $n$-GaN(0001) surface with native oxide was investigated with X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS). It is shown that hafnium creates a continuous and stable layer on GaN substrate. Thermal treatment at $850^{\circ }$C of Hf/GaN system causes decomposition of GaN and reaction of hafnium with atomic nitrogen from the substrate. XPS spectra demonstrate the reaction by a strong shift of the N 1s and Hf 4f lines. An attempt for bringing on the same reaction with molecular nitrogen under pressure of $1.2\times 10^{-6}$ mbar was not successful. UPS spectra show a metallic character of the hafnium adlayer in such instances.

Thermal reaction of phthalonitrile with hafnium powder under iodine monobromide (IBr) yields a new type molecule: bis(hafnium(IV) stapled phthalocyanine) derivative complex. X-ray single crystal analysis shows that the complex molecule consists of two hafnium phthalocyanine units bridged by the unique internal ligand that stapled by two carbon–carbon $\sigma$ bonds to both HfPc-units. The internal dianionic ligand consists of two fragments, each of them present the three fourth part of phthalocyaninate ring. Both fragments are linked together through the bridging 1,2-di[amine(imine)methyl]benzene. The X-ray conformation of the bis(hafnium(IV) stapled phthalocyanine) derivative complex cation is confirmed by DFT calculations. An absence of the Q-band in the UV-vis spectrum, the typical band for the fully delocalized $\pi$-electron aromatic phthalocyaninato(2-) ring system, indicates on drastic modification of the chromophore in this Hf-phthalocyanine complex that was confirmed by TD DFT calculations.