Computational and experimental studies of diffusion in monoclinic HfO2

Research on hafnia and zirconia has received a boost in the last two decades, mainly because of their electrical properties. As materials with high dielectric permittivity and a wide band-gap, they can replace SiO2 in Si-based semiconductor devices as the gate dielectric, and they can be employed as the insulator in metal—insulator—metal structures, showing memristive behavior.[1,2] Anion, and possibly cation, transport is of fundamental importance for the annealing of such devices and the proposed mechanism of resistive switching (filament switching in the case of HfO2).[2,3] In this study, we investigated both cation and anion diffusion in HfO2 using diffusion experiments, with subsequent determination of the diffusion profiles by Secondary Ion Mass Spectrometry (SIMS). For the diffusion of oxygen in dense ceramics of monoclinic HfO2,, (18O/16O) isotope exchange anneals were performed in the temperature range 573 ≤ T / K ≤ 973 at an oxygen partial pressure of pO2 = 200 mbar.[4] All measured isotope profiles exhibited two features: the first feature, closer to the surface, was attributed to slow oxygen diffusion in an impurity silicate phase; the second feature, deeper in the sample, was attributed to oxygen diffusion in a homogeneous bulk phase. The activation enthalpy of oxygen tracer diffusion in bulk HfO2 was found to be ΔHD* ≈ 0.5 eV. In contrast to oxygen diffusion, diffusion of cations in HfO2 and other oxide-ion conductors is experimentally much more challenging. It is slow, requiring, therefore, high temperatures and long diffusion times. In the case of HfO2, there is also the problem of Si impurities (see above), which are hard to get rid of in ceramic samples. To alleviate these problems somewhat, we directly investigated the diffusion of Zr in thin films of nanocrystalline, monoclinic HfO2, prepared by Atomic Layer Deposition (ALD) and coupled with a sputtered top layer of ZrO2 as a diffusion source. Diffusion experiments were performed in the temperature range 1173 ≤ T / K ≤ 1323 in air. All measured diffusion profiles exhibited bulk diffusion and fast grain-boundary diffusion. Using numerical simulations, we were able to describe the profiles and extract diffusion coefficients for Zr diffusion in bulk HfO2 and along its grain boundaries. The activation enthalpies of diffusion in both cases were, surprisingly, the same at ΔHDb/Dgb ≈ 2.1 eV. They are also much lower than activation energies predicted by static atomistic simulations.[5] In order to aid the interpretation of the experimental data, we conducted atomistic simulations of cation diffusion in HfO2. Specifically we performed Molecular Dynamics (MD) simulations using the empirical pair potentials derived by Catlow and Lewis.[6,7] These potentials are suitable for describing defect behaviour in HfO2.[8,9] The activation enthalpy of Hf diffusion in bulk HfO2 we obtained from the MD simulations agrees exceedingly well with the experimental results: ΔHD* ≈ 2 eV. The reasons for this behaviour are discussed. [1]: V. A. Gritsenko et al., Phys. Rep 613, 1 (2016). [2]: R. Waser et al., Adv. Mater. 21, 2632 (2009). [3]: S. Uhlenbruck et al., Solid State Ionics 180, 418 (2009). [4]: M. P. Mueller, R. A. De Souza, Appl. Phys. Lett. 112, 051908 (2018). [5]: S. Beschnitt et al., J. Phys. Chem. C 119, 27307 (2015). [6]: C. R. A. Catlow, Proc. R. Soc. Lond. A. 353(1675), 533 (1977). [7]: G. Lewis, C. R. A. Catlow, J. Phys. C: Solid State Phys. 18(6), 1149 (1985). [8]: M. Schie et al., J. Chem. Phys. 146, 094508 (2017). [9]: M. Schie et al., Phys. Rev. Mat. 2, 035002 (2018

In situ investigation of copper corrosion in acidic chloride solution using atomic force - scanning electrochemical microscopy

The anodic dissolution of pure copper surfaces in acidic chloride solution has been monitored in-situ using combined atomic force – scanning electrochemical microscopy (AFM-SECM). Here, the initial studies performed on model copper-modified substrates have been extended to the investigation of bulk copper samples used in industrial settings. The local release of Cu2+ ions was monitored through electrochemical reduction and deposition of the metal ions on the conductive frame of the AFM-SECM probe. Simultaneous monitoring of the topographical changes due to the corrosion process allowed the distinction and correlation of local passivation and pitting phenomena. The extent of the attack was estimated by anodic stripping of the copper metal deposited at the probe

In situ monitoring of pit nucleation and growth at iron passive oxide layer using combined atomic force and scanning electrochemical microscopy

Generation of single corrosion pits and in situ monitoring of pit growth on iron exposed to 0.5 M NaCl solution was achieved using combined atomic force - scanning electrochemical microscopy (AFM-SECM). Pits as small as 2.7 μm in diameter were formed at arbitrary locations on the substrate by local generation of highly concentrated nitric acid in the vicinity of the AFM-SECM probe. Addition of nitrite ions to the environment, which act as corrosion inhibitors for iron, ensures passivation of the metal, and hinders metal corrosion despite exposure to the chloride-containing media. Localized acidification was achieved by oxidizing nitrite ions at the probe. Acidification in combination with the high chloride content in the solution leads to a local rapid attack at the surface and pit generation below the AFM-SECM probe. Besides improved spatial resolution and precise control of the pit nucleation site, combined AFM-SECM allows simultaneous imaging of the generated pits by the AFM tip

Power supply for battery charging

В системах энергоснабжения космических аппаратов очень много внимания уделяется системам заряда аккумуляторных батарей. В состав данных систем входят фотоэлектрические преобразователи, преобразующие энергию солнца в электрический ток. Данные преобразователи имеют крайне низкие энергетические показатели. Предлагаемая работа направлена на повышение эффективности заряда аккумуляторных батарей, посредством применения резонансного инвертора.In the space power systems, much attention is paid to battery charging systems. The composition of these systems includes photoelectric converters that convert the energy of the sun into electric current. These converters have extremely low energy performance. The proposed paper is aimed at increasing the efficiency of batteries chargers, by applying a resonant inverter

Simultaneous pit generation and visualization of pit topography using combined atomic force-scanning electrochemical microscopy

Combined atomic force microscopy – scanning electrochemical microscopy (AFM-SECM) is for the first time used to generate single corrosion pits on passivating iron surfaces in the micrometer range. The AFM-SECM probe locally generates nitric acid during the oxidation of nitrite ions with the release of protons at selected sites on the surface of the otherwise passive metal. High confinement of passive film breakdown is achieved from the combination of a small probe size and the inhibiting properties of non-reacted nitrite ions on the surrounding passivated surface. Simultaneous visualization of pit nucleation and propagation can be obtained in the same solution without changing the probe by AFM

Boxnep - модульный подводный робот перспективных технологий

The article discusses the relevance of the underwater vehicles are able to solve a wide range of problems. The decision puts in a basis of the research is designing a modular underwater robot. It allows to make a mounting of various equipment and testing it in the water medium. The paper deals with the concept of the robot and its characteristics

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration

Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results