Search results for " Hafnium"

Synergistic Use of Electrochemical Impedance Spectroscopy and Photoelectrochemical Measurements for Studying Solid State Properties of Anodic HfO2

2017

Within the past years, intense research has been carried out on HfO2 as high k material, promising candidate to replace SiO2 as gate dielectric in CMOS based devices (1), and as metal oxide for resistive random access memory (ReRAM) (2). For both technological applications compact, uniform and flat oxides are necessary, and a detailed understanding of their physical properties as a function of the fabrication conditions is strongly. Hafnia performance can be significantly influenced by carrier trapping taking place at pre-existing precursors states (induced by oxygen vacancies, interstitial ions, impurities acting as dopants), or by self-trapping in a perfect lattice, where the potential we…

Zirconium–hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water

2016

The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidicwaters are sulphate dominatedwith different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr a nd Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters. Y-Ho and Zr-Hf (twin pairs) have a…

Geochemistry of Zr, Hf and REE in extreme water environments: hyperacid, hyper saline and lake waters in hydrothermal systems

This PhD thesis concerns the geochemistry of Zr, Hf and REE in extreme water environments characterized by a wide spectrum of chemical physical-parameters and compositions. The investigations were carried out in hypersaline waters covering a wide range of Eh values along Dead Sea Fault (Israel), in hyperacid waters circulating in Nevado del Ruiz volcano-hydrothermal system (Colombia) and in CO2-rich waters belonging to the Pantelleria volcano-hydrothermal system (Italy), including the alkaline lake “Specchio di Venere” formed within a calderic depression. The wide spectrum of chemical-physical conditions and various water chemical compositions interacting with different solid phases allowed…

Local structural investigation of hafnia-zirconia polymorphs in powders and thin films by X-ray absorption spectroscopy

2019

Björn Matthey (Fraunhofer IKTS, Dresden) is acknowledged for providing HfO2 and ZrO2 powders on short notice after DESY’s renowned customs office punished us. Parts of this research were carried out at Petra III at DESY, a member of the Helmholtz Association (HGF). The experiments on single Si:HfO2 thin film samples were performed at the CLAESS beamline at ALBA Synchrotron with the collaboration of ALBA staff. We would like to thank Edmund Welter for assistance (in using beamline P65) and DESY for enabling this research for proposal no. 20160591 and for travel support. T.S. acknowledges the German Research Foundation (DFG) for funding this work in the frame of the project “Inferox” (project…

Zirconium, Hafnium and Rare Earths behaviour during the transport in volcanic fluids. Geochemical effects throughout the sublimation and after intera…

This research indicates the fate of Zr, Hf and Rare Earths during their sublimation from the high-temperature gas phase (100° - 420 °C), in volcanic systems associated with different geodynamic regimes, and processes associated with volcanic sublimation representing the last natural “inorganic” interface where a detailed investigation into the behaviour of Rare Earths had never been conducted. The research was carried out in active volcanic systems at Vulcano (Aeolian Islands, Italy), Santorini (Cyclades Islands, Greece), Phlegrean Fields (Italy), Tenerife (Canary Islands, Spain) and Fogo Island (Cape Verde) where both fumaroles and thermal waters from submarine springs and inland wells wer…

Geochemistry of REE, Zr and HF in a wide range of pH and water composition: The Nevado del Ruiz volcano hydrothermal system (Colombia)

2015

International audience; The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidic waters are sulphate dominated with different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr and Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters.Y–Ho and Z…

Search for very long-lived isomers in the hafnium-tungsten region

2000

Targets of ${}^{48}\mathrm{Ca}$ have been bombarded with ${}^{134,136}\mathrm{Xe}$ beams as part of a search for long-lived, high-K states in well-deformed nuclei with $A\ensuremath{\approx}180.$ Several known isomers were observed by off-line \ensuremath{\gamma}-ray detection, and limits have been established for high-K isomer production in various isotopes of hafnium $(A=175--178),$ tantalum $(A=177--181),$ and tungsten $(A=177--181).$