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Because of their full compatibility with CMOS technology, HfO2-based ferroelectrics, and especially Hf0.5Zr0.5O2 (HZO), attract a lot of attention. However, the overwhelming majority of measurement techniques provides only information about the cumulative electrical response of many domains of HZO, i.e., at the macroscopic level. So far, only piezoresponse force microscopy technique was applied to visualize distinct ferroelectric domains in HZO and to analyze the local switching behavior in the microscopic level. This work introduces the possibility of using electron beam-induced current (EBIC) technique in the scanning electron microscope to visualize the gradual polarization reversal of HZO and to obtain the local polarization dynamics. We show that although the local EBIC signal is affected by surrounding domains, studying the variations in the ferroelectric response of individual domains as well as the spread of the local stiffness and local imprint is possible by this method. Besides, we show the connection between the EBIC current and an electric field across passive non-ferroelectric layers at interfaces between HZO and metal electrodes, which opens up additional opportunities to use the EBIC technique for investigations of interface-dependent properties of HZO ferroelectrics in the future.

UDC 517.925 We establish new results concerning the conditions of existence of one class of monotonous solutions of a two-term nonautonomous differential equation of the the second-order with a rapidly varying nonlinearity. These results essentially supplement the results of previous researches.

Recently, the extensive study of the platinum group metal oxide electrodes for TiN replacement in Hf0.5Zr0.5O2 (HZO)-based ferroelectric memory stacks began. In this work, we use high sensitivity of x-ray photoelectron spectroscopy to the interface chemical and electronic states to investigate the chemistry and band alignment between HZO and RuO2, which is one of the most suitable noble metal oxide electrodes. We report that RuO2 is easily reduced to metallic Ru during the atomic layer deposition (ALD) of HZO because of the chemical reaction between the oxygen stored in RuO2 and metallic precursors used for HZO deposition. This process makes it impossible to use RuO2 as a bottom electrode, when HZO is grown by the conventional thermal ALD process (with H2O as a reactant). At the same time, RuO2 may be effectively conserved if one uses more active oxygen reactants for the HZO growth because of the re-oxidation of the newly formed Ru. RuO2 is also effectively conserved at the top interface, at least within the thermal budget of the growth of all functional layers. We also report the detailed investigation of the band alignment between RuO2 and HZO in both type of stacks (with reduced and conserved RuO2) and both interfaces with HZO (top and bottom), which may be useful for the understanding of the ferroelectric properties of the related stacks in the future. In addition, the potential of RuO2 utilization for the reliability improvement of HZO-based stacks is discussed.

Resistive switching (RS) device behavior is highly dependent on both insulator and electrode material properties. In particular, the bottom electrode (BE) surface morphology can strongly affect RS characteristics. In this work, Ru films with different thicknesses grown on a TiN layer by radical-enhanced atomic layer deposition (REALD) are used as an inert BE in TaOx-based RS structures. The REALD Ru surface roughness is found to increase by more than 1 order of magnitude with the increase in the reaction cycle number. Simultaneously, a wide range of RS parameters, such as switching voltage, resistance both in low and high resistance states, endurance, and so forth, monotonically change. A simplified model is proposed to explain the linkage between RS properties and roughness of the Ru surface. The field distribution was simulated based on the observed surface morphologies, and the resulting conducting filament formation was anticipated based on the local field enhancement. Conductive atomic force microscopy confirmed the theoretical expectations.

The purpose of this work was to reveal the intra- and inter-individual variability of the urine proteomic composition and of biochemical blood parameters in cosmonauts with different preflight autonomic status when they are back to Earth (on the 1st and 7th day after space flight). The objects of the study were 5-min samples of electrocardiogram (ECG) at rest and urine and venous blood samples, obtained in the same timeline from twelve male cosmonauts (age 46.5 ± 3.4 years), who performed space flights (SF) with duration 169–199 days onboard the Russian segment of the International Space Station (ISS). Two groups with different sympathetic-parasympathetic balance were identified (each consists of 6 cosmonauts) by the results of preflight heart rate variability (HRV) analysis. We have revealed in groups of cosmonauts with preflight predominance of sympathetic or parasympathetic tone the significant differences in the directionality of changes on days 1 and 7 after the SF as compared to the preflight values in three proteins (from total amount around 200): alpha-1 subunit of collagen type VI, Mucin 1, Cadherin-13. A set of biochemical parameters, unidirectionally changing with these proteins, was different in classified groups. Direct bilirubin, potassium and total calcium move unidirectionally with collagen, direct bilirubin, potassium – with mucin, and uric acid, ferrum, alpha-1, KFK, potassium - with cadherin in group with a sympathetic tone. Potassium, ferrum, alpha-1 move unidirectionally with collagen, amylase, KFK, AST, urea, inorganic phosphate, glucose, alkaline phosphatase, ionized calcium – with mucin, and total ferrum biding capacity, transferrin, glucose gamma globulin transferase - with cadherin in group with parasympathetic predominance. Probably, differences between groups in the concentration of these proteins and their different relationship with some biochemical parameters reflect different ways to achieve the same goal - adaptation to a complex of SF factors and re-adaptation after returning to Earth.

Urine chromatography–mass spectrometry and a heart rate variability (HRV) analysis were performed in 13 healthy males (age 28 ± 4 years, height 174 ± 1 cm, weight 67.9 ± 1.5 kg). Mathematical and bioinformatics analyses identified the proteins that are associated with the condition of the cardiovascular system and the autonomic regulation of the heart rate in the total protein aggregate. The set included serotransferrin, tyrosine-protein kinase receptor UFO, prostatic acid phosphatase, secreted and transmembrane protein 1, cell adhesion molecule 4, galectin-3-binding protein, immunoglobulin heavy constant alpha 1, matrix remodeling-associated protein 8, and biotinidase. Associations were for the first time studied for protein markers of the heart rate autonomic regulation. Proteomics data were used to describe the indicators of the heart rate physiological regulation in the urine proteome of healthy young males.

The feasibility of growing atomically thin MoS2 films (down to two monolayers) on several tens of cm2 area was demonstrated by first depositing the MoO3 thin film by using an atomic layer depositio...

We establish conditions for the existence of one class of monotone solutions of two-term nonautonomous differential equations of the second order with rapidly varying nonlinearities, as well as the asymptotic representations of these solutions and their first-order derivatives as t ↑ ω (ω ≤ + ∞).

The method of deposition from the gas phase is applied to the synthesis of thin films of molybdenum disulfide. It was established that varying the rate of temperature rise in the course of the synthesis affects the character of growth and the structure of the layers formed. With a decrease in the rate of temperature rise, a transition from standard two-dimensional to screw growth of MoS2 films is observed. MoS2 films produced as a result of screw growth have a high density of edge states, which makes them promising for use in catalysis.

The discovery of ferroelectricity in hafnium oxide has revived the interest in ferroelectric memories as a viable option for low power non-volatile memories. However, due to the high coercive field of ferroelectric hafnium oxide, instabilities in the field cycling process are commonly observed and explained by the defect movement, defect generation and field induced phase transitions. In this work, the optical and transport experiments are combined with ab-initio simulations and transport modeling to validate that the defects which act as charge traps in ferroelectric active layers are oxygen vacancies. A new oxygen vacancy generation leads to a fast growth of leakage currents and a consequent degradation of the ferroelectric response in Hf0.5Zr0.5O2 films. Two possible pathways of the Hf0.5Zr0.5O2 ferroelectric property degradation are discussed.

We establish new conditions for the existence of slowly varying solutions of a second-order differential binomial nonautonomous equation with rapidly varying nonlinearity. We also determine the asymptotic representations for these solutions and their first derivatives as t ↑ ω, ω ≤ + ∞.

The study of proteins - potential markers, associated signal transduction pathways, and their targets - provides a new understanding of the fundamental mechanisms occurring at the level of regulatory processes in the cardiovascular system (CVS), especially in space flight, as well as in model experiments that reproduce its individual effects on the human body. The article presents the results of studies in an experiment with 120-day isolation within the framework of the SIRIUS project in which 6 volunteers aged 28 to 44 years (three men and three women) participated. SIRIUS (Scientific International Research in Unique Terrestrial Station) is the international research project, which studies the issues of biomedical and psychological support of long-term manned space flights. The possible involvement of collagen different types, an extracellular matrix protein, in the mechanisms of autonomic regulation of the CVS was studied. Using chromatic mass spectrometry in urine samples and analysis of heart rate variability, we have established that the extracellular matrix collagen, which is present, in particular, in the structure of the blood vessel wall, are markers associated with the modulating effect of the autonomic nervous system on the regulatory mechanisms of blood circulation. We hypothesized that these proteins may be a biomarker of the autonomic balance in the regulatory mechanisms of the circulatory system. In addition, these proteins can also be markers of the aging process, which increases the risks of developing autonomic dysfunction of the cardiovascular system (dominance of sympathicotonia) and changes in the quality of the tissue of the heart muscle and blood vessels, provoking the development of prenosological conditions and diseases of the cardiovascular system.

The purpose of the study was to investigate the regulatory and metabolic changes in the circulatory system when simulating microgravity conditions in a five-day dry immersion. These changes reflect the adaptation processes characteristic for the initial stages of a space flight or a short-duration space flight. Studies were conducted with 13 healthy male volunteers aged 21 to 29 years. The assessment of regulatory and metabolic processes in the circulatory system was based on the heart rate variability (HRV) and urine proteomic profile analysis. It was found that the restructuring of hemodynamics during 5 days hypogravity begins with the inclusion of the nervous circuit of regulation, and for manifestations at the body fluids protein composition level and activation of the metabolic regulation, these periods are apparently insufficient. Perhaps this is due to the fact that the metabolic regulation, being evolutionarily ancient and genetically determined, is more stable and requires more time for its pronounced activation when stimulated by extreme life conditions.

This work demonstrates by in vacuo X-ray photoelectron spectroscopy and grazing-incidence X-ray diffraction that Ru(EtCp)

The microstructures of amorphous and polycrystalline ferroelectric Hf0.5Zr0.5O2 films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film consists of an “incompletely mixed” solid solution of metallic oxides HfO2 and ZrO2. After rapid thermal annealing, the mixed Hf0.5Zr0.5O2 oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands are formed in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO2 and ZrO2. The presence of the HfO2 and ZrO2 phases in the Hf0.5Zr0.5O2 films is also detected by ellipsometry.

We establish conditions for the existence of one class of solutions of two-term nonautonomous second-order differential equations with rapidly varying nonlinearities and obtain the asymptotic representations for these solutions and their first-order derivatives as t ↑ ω(ω ≤ + ∞).

Because of their full compatibility with the modern Si-based technology, the HfO2-based ferroelectric films have recently emerged as viable candidates for application in nonvolatile memory devices. However, despite significant efforts, the mechanism of the polarization switching in this material is still under debate. In this work, we elucidate the microscopic nature of the polarization switching process in functional Hf0.5Zr0.5O2-based ferroelectric capacitors during its operation. In particular, the static domain structure and its switching dynamics following the application of the external electric field have been monitored with the advanced piezoresponse force microscopy (PFM) technique providing a nm resolution. Separate domains with strong built-in electric field have been found. Piezoresponse mapping of pristine Hf0.5Zr0.5O2 films revealed the mixture of polar phase grains and regions with low piezoresponse as well as the continuum of polarization orientations in the grains of polar orthorhombic ph...

Hf0.5Zr0.5O2 thin films are one of the most appealing HfO2-based ferroelectric thin films, which have been researched extensively for their applications in ferroelectric memory devices. In this work, a 1 mol % La-doped Hf0.5Zr0.5O2 thin film was grown by plasma-assisted atomic layer deposition and annealed at temperatures of 450 and 500 °C to crystallize the film into the desired orthorhombic phase. Despite the use of a lower temperature than that used in previous reports, the film showed highly promising ferroelectric properties—a remnant polarization of ∼30 μC/cm2 and switching cycle endurance up to 4 × 1010. The performance was much better than that of undoped Hf0.5Zr0.5O2 thin films, demonstrating the positive influence of La doping. Such improvements were mainly attributed to the decreased coercive field (by ∼30% compared to the undoped film), which allowed for the use of a lower applied field to drive the cycling tests while maintaining a high polarization value. La doping also decreased the leakage...

We establish the conditions for the existence of one class of solutions of a nonautonomous binomial differential equation of the second order with rapidly varying nonlinearity and the asymptotic representations for these solutions and their first derivatives as t ↑ ω (ω ≤ +∞).

Retention of the storing polarization state at elevated temperatures (typically 85–105 °C) as well as the ability to rewrite and subsequently read it are an essential property of usable HfO2-based ferroelectrics for ferroelectric random access memory implementation. This work shows that retention loss in TiN/Hf0.5Zr0.5O2 (HZO)/TiN capacitors is highly dependent on the duration of pulses that are used for measurements, i.e., there is better retention of the same state (SS), new same state (NSS), and opposite state (OS) for longer pulses. The root cause of this phenomenon is the dynamic recovery of the imprint, which happens during the first long SS measurement. This may be due to the fast re-injection of charges injected from the electrode and trapped in the HZO during storage at elevated temperatures. Such dynamic imprint recovery underlies the best NSS behavior compared to other states and may affect the worst retention loss of the OS.

In this work, we report on the electron transport properties of ultrathin (~2.5nm) ferroelectric polycrystalline Hf0.5Zr0.5O2 (HZO) films grown by the Atomic Layer Deposition (ALD) technique directly on the highly doped Si substrate. On the devices with TiN top electrode we demonstrate the reversible electroresistance change R/R up to 3 across HZO layer following the polarization reversal. We further correlate the electroresistance switching with the polycrystalline structure of the the HZO layer, the polarization measurements, the current lateral distribution over the HZO layer as well as DFT calculations of the electronic band structure. Such analysis reveals that the polarization switching in ferroelectric HZO grains contribute to the current transport in TiN/HZO/n+-(p+-)Si devices. Display Omitted Ultrathin ferroelectric HZO films exhibit the electroresistance change effect.Electron transport properties are defined by specific grains of monoclinic phase.Electron transport modulation model for ultrathin hafnium oxide films is proposed.

We study the charge transport mechanism in ferroelectric Hf0.5Zr0.5O2 thin films. Transport properties of the leakage currents in Hf0.5Zr0.5O2 are described by phonon-assisted tunneling between traps. Comparison with transport properties of amorphous Hf0.5Zr0.5O2 demonstrates that the transport mechanism does not depend on the crystal structure. The thermal trap energy of 1.25 eV and optical trap energy of 2.5 eV in Hf0.5Zr0.5O2 were determined based on comparison of experimentally measured data on transport with simulations within phonon-assisted tunneling between traps in dielectric films. We found that the trap density in ferroelectric Hf0.5Zr0.5O2 is slightly less that one in amorphous Hf0.5Zr0.5O2. A hypothesis that oxygen vacancies are responsible for the charge transport in Hf0.5Zr0.5O2 is confirmed by electronic structure ab initio simulation.

Early diagnosis of diseases and conditions undesirable in terms of flight safety in senior pilots is tightly linked with the evaluation of disease risks. Prenosological diagnostics is focused on borderline states that may pass from health to disease (prenosology and premorbidity) and, vice versa, from disease to recovery (post-nosology). Regarding health as a vital adaptation reserve, prenosology diagnostics is concerned with the ability of the body to adapt to the environment rather than develop a disease. A constant drain of adaptation reserves may become the reason for increased risks of disease. Heart rate variability analysis is one of the instruments of prenosological diagnostics. The paper discusses the applicability of the space-medicine oriented probabilistic approach to the evaluation of adaptation risks by medical expert assessment boards certifying civil pilots. The results of two series of investigations showed increased adaptation risks and reduced functional reserves in pilots found unfit to continue their careers.

For the decade, ferroelectric hafnium oxide films are attracting the interest as a promising functional material for nonvolatile ferroelectric random access memory due to full scalability and complementary metal-oxide-semiconductor integratability. Despite the significant progress in key performance parameters, particularly, the readout charge and voltage as well as the endurance, the developed devices can only be implemented by the electronics industry if they exhibit a standard retention time of 10 years. Material engineering modifies not only target ferroelectric properties, but also the retention time. To understand how to maintain the sufficient retention, the physical mechanism behind it should be clarified. For this purpose, we have fabricated the capacitor memory cell with a high rate of retention loss. Comparing the device performance with the results of capacitance transient spectroscopy, operando hard X-ray photoelectron spectroscopy and in situ piezoresponse force microscopy, we have concluded that the retention loss is caused by the accumulation of the positively charged oxygen vacancies at the interfaces with capacitor electrodes. The redistribution of charges during long-term storage of information is fully defined by the domain structure in memory cell.

We report the influence of an ultrathin Ru bottom electrode on ferroelectric properties of fully atomic layer deposition (ALD)-grown Hf0.5Zr0.5O2 (HZO) and La-doped Hf0.5Zr0.5O2 (HZLO)-based ferroelectric capacitors. We show that the Ru bottom electrode deposited by radical enhanced ALD (REALD) improves the remanent polarization of both capacitors considerably. The origin of such a phenomenon is established by grazing-incidence and symmetrical θ–2θ x-ray diffraction measurements. HZO films on Ru exhibit the orthorhombic phase, which is highly (002)-textured in the out-of-plane direction as compared to HZO on TiN. HZLO films demonstrate the rise of (111) intensity of the orthorhombic phase when it is grown on Ru. Both types of capacitors with Ru exhibit a lower wake-up degree as compared to the ones with TiN, which is assumed to be due to the difference in the bottom interface properties. At the same time, both HZO and HZLO on Ru suffer from the relatively early breakdown during electric field cycling, which is presumably due to the high surface roughness of REALD Ru. Taking into account the continuous search for the new precursor's chemicals and ALD processes for Ru, which would be able to provide smother films, ALD Ru might be promising for the hafnium oxide-based ferroelectric random access memory.

The mechanism responsible for the charge transport in thin ferroelectric Hf0.5Zr0.5O2 films has been studied. It is shown that in these films the transport mechanism is phonon-assisted tunneling between the traps. The optimal thickness of dielectric film for TiN/Hf0.5Zr0.5O2/Pt structures is determined. As a result of comparing the experimental current–voltage (I–V) characteristics of TiN/Hf0.5Zr0.5O2/Pt structures with the calculated ones, the thermal and optical energies of the traps are determined and the concentration of the traps is estimated. A comparison between the transport properties of ferroelectric and amorphous Hf0.5Zr0.5O2 films is carried out. It is shown that the charge transport mechanism in this dielectric does not depend on its crystalline phase. A method for decreasing leakage currents in Hf0.5Zr0.5O2 is proposed. A study of the resource of repolarization cycles for TiN/Hf0.5Zr0.5O2/TiN metal-dielectric-metal (MDM) structures fully grown by atomic layer deposition (ALD) has been carried out.

The structural and electrical properties of materials based on hafnium oxide grown by atomic layer deposition (ALD) are analyzed. The possibility and prospects of the use of their nanoscale films in nonvolatile memory are considered. The possibility of scaling Ferroelectric random access memory (FRAM) to subμm dimensions while preserving the ferroelectric properties is shown.

Trends in the development of current concepts of health as the ability to adapt require personalization and a preventive approach in the evaluation and prognostication of individual health. This can be put into practice on the basis of a prenosological approach, which is necessary in occupational medicine and physiology, especially in aviation and space medicine. We present here an analysis of data from space and terrestrial model studies of autonomic regulation, and data on heart rate variability are interpreted in relation to the concept of adaptation risk and is application to health assessment. Methods for individual prenosological monitoring have shown to have high diagnostic effectiveness.

A long-term eco-medical monitoring was undertaken from 2009 through 2011 as part of the MARS-500 satellite project. One of its major objectives was to conduct field testing of innovative technologies for assessment of human physiological status. The monitoring protocol represented a replica of that in the experiment with 520-day isolation. Heart Wizard Mars-500 is a telemedical health assessment system based on heart rate variability (HRV) analysis. Prenosology diagnosis using Heart Wizard Mars-500 has been tested in the United States and Canada. Prenosology monitoring is aimed predominantly to estimate the potential risks of maladaptation. Our results further validate diagnostic comprehensiveness of HRV analysis, in particular, during long-term systematic health monitoring, and when functional HRV tests results are compared and contrasted with entries in the health and lifestyle questionnaire. Heart Wizard Mars-500 is a simple and easy system for home use. Individual prenosology monitoring to assess the dynamics of personal functional state and detect potential risk factors may inspire personal changes in the way of life and, thus, improve one’s health and life quality.

Display Omitted Hf0.5Zr0.5O2 films with wide range of thickness were grown by ALD.Structural and electrical properties were studied after PMA and PDA.Ferroelectricity achievement in case of electrode-free annealing was demonstrated.The difference of structural properties in case of PMA and PDA was provided.The explanation of films structural difference after PMA and PDA was proposed. The structural and electrical properties of Hf0.5Zr0.5O2 thin films after post deposition and post metallization annealing were investigated. The possibility of the annealing without top electrodes for attainment of ferroelectric properties in Hf0.5Zr0.5O2 thin films was demonstrated. It was, however, shown, that the annealing in presence of top electrode leads to the more preferable crystallization to polar o-phase and the increase in the remanent polarization value. The influence of the film thickness on the structural and ferroelectric properties was studied both after post metallization and post deposition annealing. The optimal Hf0.5Zr0.5O2 thickness was found to be equal to ~19nm for electrode free annealing, which is promising value for modern nanoscale ferroelectric devices.

The charge transport mechanism in thin amorphous and ferroelectric Hf0.5Zr0.5O2 films has been studied. It has been shown that the transport mechanism in studied materials does not depend on the crystal phase and is phonon-assisted tunneling between traps. The comparison of the experimental current–voltage characteristics of TiN/Hf0.5Zr0.5O2/Pt structures with the calculated ones provides the trap parameters: thermal energy of 1.25 eV and the optical energy of 2.5 eV. The trap concentration has been estimated as ~1019–1020 cm–3.

This work demonstrates by in vacuo X-ray photoelectron spectroscopy and grazing-incidence X-ray diffraction that Ru(EtCp)2 and O* radical-enhanced atomic layer deposition, where EtCp means the ethylcyclopentadienyl group, provides the growth of either RuO2 or Ru thin films depending on the deposition temperature (Tdep), while different mechanisms are responsible for the growth of RuO2 and Ru. The thin films deposited at temperatures ranging from 200 to 260 °C consisted of polycrystalline rutile RuO2 phase revealing, according to atomic force microscopy and the four-point probe method, a low roughness (∼1.7 nm at 15 nm film thickness) and a resistivity of ≈83 µΩ cm. This low-temperature RuO2 growth was based on Ru(EtCp)2 adsorption, subsequent ligand removal, and Ru oxidation by active oxygen. The clear saturative behavior with regard to the precursor and reactant doses and each purge time, as well as the good step coverage of the film growth onto 3D structures, inherent to genuine surface-controlled atomic layer deposition, were confirmed for the lowest Tdep of 200 °C. However, at Tdep = 260 °C, a competition between film growth and etching was found, resulted in not-saturative growth. At higher deposition temperatures (300-340 °C), the growth of metallic Ru thin films with a resistivity down to ≈12 µΩ cm was demonstrated, where the film growth was proved to follow a combustion mechanism known for molecular oxygen-based Ru growth processes. However, this process lacked the truly saturative growth with regard to the precursor and reactant doses due to the etching predominance.

© 2017 IEEE. Recent advancements in the field of space medicine and technology have extended the boundaries of space travel, presenting humankind with the ability to explore undiscovered habitats. As humans embark on long range missions, adaptation mechanisms will be put to the test, challenging provision of medical care in space. To date, a vast amount of knowledge has been accumulated through a series of experiments, both in terrestrial simulation environments and space missions on the ISS. As a result, functional health state algorithm has been developed and validated by IBMP, to identify transitional states between health and disease. Significant limitations on provision of medical care in space are imposed due to retrospective data processing and analysis techniques. Some of these limitations can be addressed by the proposed instantiation of the functional state algorithm within the Online Analytics component of the Artemis platform, to enhance clinical decision support systems during spaceflight.