Films of hafnium oxide HfOx with a thickness of about 40 nm were obtained by electron beam sputtering at di erent oxygen ow rates in the chamber. The electrophysical properties of lms in air and vacuum were studied. It is shown that the temperature dependences of lm conductivity, measured in vacuum inthe temperature range from 20 to 180 ◦C, have an activation character with an activation energy of 0.82 ±0.02 eV. It has been suggested that charge transfer in the resulting lms is determined by the activation of electrons into the conduction band from the donor level associated with oxygen vacancies. It was found that the conductivity of lms in air changes greatly with varying oxygen ow, while in vacuum the conductivity is practically independent of the oxygen ow. This indicates signi cant di erences in the surface properties of lms obtained at di erent oxygen ows in the chamber during the deposition process.
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 no. MI 1247/11-2). B.J., J.L.J., and U.S. acknowledge funding from the Army Research Office through contract number W911NF-15-1-0593. This work was performed in part at the Analytical Instrumentation Facility (AIF) at North Carolina State University, which is supported by the State of North Carolina and the U.S. National Science Foundation (award number ECCS-1542015). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI). ; Despite increasing attention for the recently found ferro- and antiferroelectric properties, the polymorphism in hafnia- and zirconia-based thin films is still not sufficiently understood. In the present work, we show that it is important to have a good quality X-ray absorption spectrum to go beyond an analysis of the only the first coordination shell. Equally important is to analyze both EXAFS and XANES spectra in combination with theoretical modelling to distinguish the relevant phases even in bulk materials and to separate structural from chemical effects. As a first step toward the analysis of thin films, we start with the analysis of bulk references. After that, we successfully demonstrate an approach that allows us to extract high-quality spectra also for 20 nm thin films. Our analysis extends to the second coordination shell and includes effects created by chemical substitution of Hf with Zr to unambiguously discriminate the different polymorphs. The trends derived from X-ray absorption spectroscopy agree well with X-ray diffraction measurements. In this work we clearly identify a gradual transformation from monoclinic to tetragonal phase as the Zr content of the films increases. We separated structural effects from effects created by chemical disorder when ration of Hf:Zr is varied and found differences for the incorporation of the substitute atoms between powders and thin films, which we attribute to the different fabrication routes. This work opens the door for further in-depth structural studies to shine light into the chemistry and physics of these novel ferroelectric thin films that show high application relevance. ; DESY proposal no. 20160591; German Research Foundation MI 1247/11-2; Army Research Office W911NF-15-1-0593; State of North Carolina and the U.S. National Science Foundation (award number ECCS-1542015); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²
International audience ; In their roadmap towards the decommissioning of Fukushima Daiichi reactors, the Japanese authorities plan to start removing fuel debris by the end of 2021. To reach this objective, several RetD projects have been launched and subsidized by the Japanese government. In this framework, a French consortium (COMEX Nucleaire/ONET Technologies, CEA and IRSN) has been selected to implement RetD related to the laser cutting of Fukushima Daiichi fuel debris and related dust collection technology. Some of the key aspects of this project are to fabricate representative corium debris simulants, to test laser cutting technique on these simulants and to measure the aerosols and dusts that are released during the debris thermal cutting. This paper concentrates on the first issue.Two representative corium compositions have been selected in-vessel debris having the average of Fukushima Daiichi Unit 2 (1F2) lower head debris composition best estimates from the OECD Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF); ex-vessel debris composition chosen from DOE calculations on Fukushima Daiichi Unit 1 (1F1) molten core concrete interaction in order to maximize the concrete content and bound the possible composition space.Fission Products expected 10 years after plant shutdown have also been taken into account. As it was not possible within the current project timeframe to perform debris cutting tests with (depleted) uranium oxide, it has been necessary to simulate uranium oxide and hafnium oxide has been considered as the best option.Based on its 20 year experience in corium experimental RetD, PLINIUS platform at CEA Cadarache has been chosen to fabricate these simulants. Two blocks of 8-10 kg have been induction melted. After melting and cooling, samples have been analyzed (microstructure and chemical composition) and laser cutting of these simulant blocks has been successfully carried out.
International audience ; In their roadmap towards the decommissioning of Fukushima Daiichi reactors, the Japanese authorities plan to start removing fuel debris by the end of 2021. To reach this objective, several RetD projects have been launched and subsidized by the Japanese government. In this framework, a French consortium (COMEX Nucleaire/ONET Technologies, CEA and IRSN) has been selected to implement RetD related to the laser cutting of Fukushima Daiichi fuel debris and related dust collection technology. Some of the key aspects of this project are to fabricate representative corium debris simulants, to test laser cutting technique on these simulants and to measure the aerosols and dusts that are released during the debris thermal cutting. This paper concentrates on the first issue.Two representative corium compositions have been selected in-vessel debris having the average of Fukushima Daiichi Unit 2 (1F2) lower head debris composition best estimates from the OECD Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF); ex-vessel debris composition chosen from DOE calculations on Fukushima Daiichi Unit 1 (1F1) molten core concrete interaction in order to maximize the concrete content and bound the possible composition space.Fission Products expected 10 years after plant shutdown have also been taken into account. As it was not possible within the current project timeframe to perform debris cutting tests with (depleted) uranium oxide, it has been necessary to simulate uranium oxide and hafnium oxide has been considered as the best option.Based on its 20 year experience in corium experimental RetD, PLINIUS platform at CEA Cadarache has been chosen to fabricate these simulants. Two blocks of 8-10 kg have been induction melted. After melting and cooling, samples have been analyzed (microstructure and chemical composition) and laser cutting of these simulant blocks has been successfully carried out.
The interface-induced second-harmonic generation from ferroelectric hafnium–zirconium oxide (Hf0.5Zr0.5O2) epitaxial thin films, buffered with a La0.67Sr0.33MnO3 bottom electrode, is analyzed as a function of input and output polarization angles and the azimuthal angle of the sample for several film thicknesses. It is shown that the signal is generated mainly from the buffer side of the interface, rather than from the ferroelectric side. However, the ferroelectric film affects significantly the nonlinear optical properties of the underlying ferromagnetic buffer electrode. Several mechanisms accounting for these observations are discussed, from oxygen migration, to an electrostatic effect, including a possible modulation of the La0.67Sr0.33MnO3 magnetization by the upper ferroelectric film. ; The authors would like to acknowledge funding from the Italian Government, PRIN-TWEET (grant code 2017YCTB59), and from the Spanish Ministry of Science and Innovation, through the Severo Ochoa FUNFUTURE (CEX2019-000917-SMCIN, AEI/10.13039/501100011033), PID2020-112548RB-I00 (MCIN/AEI/10.13039/501100011033), and PID2019-107727RB-I00 (MCIN/AEI/10.13039/501100011033) projects. All authors would like to thank Silvia Picozzi (CNR-SPIN) and Christian Rinaldi (Politecnico Milano) for the useful discussions. ; info:eu-repo/grantAgreement/AGENCIA FINANCIADORA/PROGRAMA DE FINANCIACIÓN/REFERENCIA DEL PROYECTO ; Peer reviewed
Die Inhalte der verlinkten Blogs und Blog Beiträge unterliegen in vielen Fällen keiner redaktionellen Kontrolle.
Warnung zur Verfügbarkeit
Eine dauerhafte Verfügbarkeit ist nicht garantiert und liegt vollumfänglich in den Händen der Blogbetreiber:innen. Bitte erstellen Sie sich selbständig eine Kopie falls Sie einen Blog Beitrag zitieren möchten.
A startling piece of misinformation is circulating again. The thing that makes us sad about this - no, really sad - is that it comes from the American Chemical Society. You know, one of those official bodies that we'd hope would actually be informative. Even, possibly, attempt to be factually correct. You can see their warning about the elements we're going to have significant supply problems with here. We've covered this subject at book length here (it's free!).But to cut to the short version. The ACS says that there's a serious threat of running out of gallium, germanium and hafnium in the next 100 years. All of which is a heck of a surprise to any geologist or anyone actually in the metals business. So it's difficult to grasp why the chemists are in such a tizzy about it.Gallium is extracted from a Bayer Process plant. That's the stage of the aluminium business that turns bauxite, the ore (and possibly the most common component of the Earth's surface) into alumina, the oxide. The gallium in the bauxite goes into solution and with the right little doohickey it can be extracted. Which is what is done. We have - already mapped out, ready to roll - at least a 1,000 year supply of bauxite. We're not going to run out of gallium.Germanium has two sources, a byproduct from the mining of zinc from spharelite and another process which extracts from fly ash. That's the waste left over from the burning of coal. There are hundreds of millions of tonnes of fly ash lying around the countryside in vast ponds. We're simply not going to run out of germanium.Zircon is a common enough mineral, the world uses perhaps 600,000 tonnes a year, there are millennia of it out there at least. All zircon is 2 to 4% hafnium. We usually don't bother to extract it as for near all uses the two are so similar that we don't care. Sometimes we do care and so we extract the Hf from the Zr to use them separately. We extract perhaps 500 tonnes a year of the 20,000 tonnes of hafnium already incorporated in the zircon/zirconium moving through the system. We're not going to run out of hafnium.All of which is bad enough, the official sources being so horribly out of whack with reality (and as an aside, one of the reasons that state planning works so badly, it so often starts from such lack of knowledge as this). But Ga, Ge, Hf, they're not exactly at the top of the worries list for most people. But think on it, if they're this wrong about these simple things then what else is wrong in all of the other things they're saying to us?
