Papers by Peter B Mozhaev
Russian microelectronics, Dec 1, 2023
Applied Physics A, Dec 26, 2023
CeO2 thin films were grown on NdGaO3 tilted-axes substrates by pulsed laser deposition (PLD) show... more CeO2 thin films were grown on NdGaO3 tilted-axes substrates by pulsed laser deposition (PLD) showing three-dimensional graphoepitaxial (3DGE) growth in the whole studied range of substrate tilt angles γ = 5-27º. Deviations from the tangent dependence can be divided into a systematic negative part and local deviations near certain film tilt angles. The systematic deviation may be explained as the effect of completely-strained coherent growth of the bottom layers of CeO2 film. Minimization of the surface energy near the small-index crystallographic planes (012) and (013) may account for the local deviations from the calculated dependence. The width of the rocking curve and the lattice constant variation for the 3DGE CeO2 films increase almost linearly with the substrate tilt angle until 19º and decrease for higher γ. At different deposition rates the 3DGE CeO2 film exhibits three possible structures: (i) relaxed completely oxygenated films at very low deposition rate, (ii) completely ...
International Conference on Micro- and Nano-Electronics 2021, 2022
Graphoepitaxial CeO2 and Y:ZrO2 (YSZ) thin films showed re-orientation towards (012), (013) small... more Graphoepitaxial CeO2 and Y:ZrO2 (YSZ) thin films showed re-orientation towards (012), (013) small-index crystallographic planes (SIPCs) due to surface energy minimization effects, with deviation from the expected tilt angles up to 4.5º. Re-orientation of the CeO2 films towards the (012) plane was obtained for the intermediate range of deposition rate and oxygen partial pressure, providing high plasticity of the lattice of the film due to formation of oxygen vacancies, and the relatively low bonding strength of the film-substrate interface. The realization of re-orientation of the YSZ graphoepitaxial films demanded intentional suppression of the epitaxial bonding between the film and the substrate. The effect was observed both for (012) and (013) SICPs. The re-orientation is obtained easier when the film experiences additional tilting towards the substrate plane, reaching inclination angles of 2.5-4.5º. The re-orientation from the substrate plane is also possible, but such films are usually re-oriented partially, and the observed inclination angle is limited to ~0.3º. The re-oriented films show a lower spread of orientations of domains, observed as a decrease of the width of the rocking curve. The reason is the co-orienting effect of the substrate surface during growth, opposite to the mis-orienting effect of dislocations generation for ordinary graphoepitaxial films. The lattice constant normal to the epiplane experiences distortion near the surface of the film, contractive for a decrease of the final tilt angle and tensile for re-orientation from the substrate surface.
International Workshop on Superconducting Nano-Electronics Devices, 2002
The dependence of the superconducting current Is on the phase difference φ between the order para... more The dependence of the superconducting current Is on the phase difference φ between the order parameters of the two superconductors forming a Josephson junction (current phase relation - CPR) determines dynamic parameters of the Josephson junctions (JJ) such as the Josephson inductance, the microwave impedance, the spectrum of the Josephson generation and so on. Calculations of Josephson circuits behaviour are usually made assuming 1 a sinusoidal CPR Is(φ)=Icsin φ (Ic is the critical current of the JJ). On other side the superconducting phase qubits for the quantum computing included Josephson junctions with double periodic (2 φ) CPR with minima at phase values φ=0. Pure sinusoidal CPR is observed in tunnel junctions between ordinary s-wave superconductors (SIS) over a wide range of temperatures2. However, in JJ with direct (nontunnel) conductivity, like point contacts (ScS), a nearly sawtooth dependence of Is(φ) is observed at low temperature, which may be expressed in terms of Fourier components: $$ {{\rm{I}}_{\rm{S}}}\left( \varphi \right) = {{\rm{I}}_{\rm{c}}}\sum {{\delta _n}\sin \left( {n\varphi } \right)} , $$ (1) where n£1 and δn are the amplitudes of the Fourier components. The possible reason for the complex dependence of Is(φ) is the contribution of multiple Andreev reflections to the current transport. For most types of JJs the Andreev’s levels are described by the formula2’3: $$ {E_b} = \pm \Delta \surd \left( {1 - \overline D {{\sin }^2}\left( {{\varphi \mathord{\left/ {\vphantom {\varphi 2}} \right. \kern-\nulldelimiterspace} 2}} \right)} \right), $$ (2) where Δ is the superconducting gap and D is the barrier transparency.
ABSTRACT Ramp-type Josephson junctions with YBCO superconducting electrodes and PrBa2Cu2.6Ga0.4O6... more ABSTRACT Ramp-type Josephson junctions with YBCO superconducting electrodes and PrBa2Cu2.6Ga0.4O6+d(PBGCO) barriers were fabricated and characterized. The YBCO ramp junctions with 25 nm-thick barriers of PBGCO showed typical resistively- shunted-junction (RSJ)-like I-V behavior and 1s spread of less than 13% in critical current density. Differential conductance-voltage characteristics registered using a lock-in technique indicate that the resonant tunneling via localized states in the barriers plays a dominant role in the conduction process of the ramp junctions.
ABSTRACT The stability of pinned vortex systems is constantly challenged in superconductors. In t... more ABSTRACT The stability of pinned vortex systems is constantly challenged in superconductors. In this work, magneto-optical imaging was used to reveal a new type of intermittent flux behavior in films of YBa2Cu3Ox. Films were grown on tilted NdGaO3 substrates, where the terrace structure creates a high density of planar defects. The flux penetration along the terrace steps consists of numerous 1-dimensional avalanches, some starting at the film edge, some fully internal. In spite the vivid dynamics the flux front advances in accordance with the critical state model. Analysing more than 10000 avalanche events, we find a power-law size distribution and finite-size-scaling with the depth of the flux front as crossover length. The intermittent behaviour shows no threshold value in the applied field. These new characteristics largely contrast those of the thermo-magnetic avalanches observed in many superconducting films, and suggest that a different mechanism is responsible for the 1-dimensional avalanches.
Physical Review X, 2012
Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YB... more Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa 2 Cu 3 O 7-deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a power law, and data collapse is obtained by finite-size scaling, with the depth of the flux front used as crossover length. The intermittent behavior shows no threshold value in the applied field, in contrast to conventional flux jumping. The results strongly suggest that the quasi-one-dimensional flux jumps are of a different nature than the thermomagnetic dendritic (branching) avalanches that are commonly found in superconducting films.
Physica C: Superconductivity, 2006
Bi-epitaxial heterostructures YBa2Cu3Ox(YBCO)/CeO2/NdGaO3 were prepared on tilted-axes NdGaO3 sub... more Bi-epitaxial heterostructures YBa2Cu3Ox(YBCO)/CeO2/NdGaO3 were prepared on tilted-axes NdGaO3 substrates using laser ablation technique. The heterostructures were patterned for electrical measurements using photolithography and ion-beam milling. Electrical anisotropy of the YBCO film was tested on the ion-beam etched surface. Bi-epitaxial junctions with four different orientations of the bi-epitaxial border were fabricated and studied. The measured I V curves showed flux flow behavior with critical current density 2.5 × 104 A/cm2 for the twist-type junctions and 1.5 × 103 A/cm2 for [1 0 0]-tilt type junctions.
Journal of Physics: Conference Series, 2008
The characteristics are investigated of high temperature superconducting YBa2Cu3O7 (YBCO) films g... more The characteristics are investigated of high temperature superconducting YBa2Cu3O7 (YBCO) films grown on LaAlO3 (LAO) substrates being exposed a different number of times to YBCO film deposition and acid-solution-based cleaning procedures. Possible mechanisms of degradation of the substrate surface quality reflecting on the growing YBCO film parameters are discussed and analyzed.
International Workshop on Superconducting Nano-Electronics Devices, 2002
DYNAMICS OF SUPERCONDUCTING INTERFEROMETERS CONTAINING PI-JUNCTIONSVictor K. Kornev, Igor I. Solo... more DYNAMICS OF SUPERCONDUCTING INTERFEROMETERS CONTAINING PI-JUNCTIONSVictor K. Kornev, Igor I. Soloviev, Igor V. Borisenko, Peter B. Mozhaev, and Gennady A. Ovsyannikov 1. INTRODUCTION Josephson junction circuits containing n-junctions are ...
In type-II superconductors, increasing applied magnetic field penetrates gradually in the form of... more In type-II superconductors, increasing applied magnetic field penetrates gradually in the form of magnetic vortices. It is of great interest to understand the dynamics of magnetic flux in different superconducting materials, as this phenomenon can severely limit the performance of superconductors in applications. YBa2Cu3O7 − x (YBCO) is an important high-temperature superconductor, but until recently, it has been hard to make wires from it due to misalignment of superconducting grains. A solution to this problem is to deposit YBCO on vicinal substrates to better align the grains. Some of these samples show a strongly intermittent flux penetration at low temperatures. In this work, we have studied flux penetration in YBCO deposited on a 14° vicinal substrate of NdGaO3 (NGO) at different temperatures.
Physical Review Materials, Oct 9, 2018
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Superconductivity and Novel Magnetism
A deposition process for NdBa 2 Cu 3 O y thin films by laser ablation at decreased deposition tem... more A deposition process for NdBa 2 Cu 3 O y thin films by laser ablation at decreased deposition temperature was developed using substitution of oxygen with argon in the chamber during deposition. A low deposition rate is the crucial factor to obtain high-quality NBCO films. The Nd/Ba cation disorder in the film can be suppressed by an increase of the deposition temperature or by a decrease of the oxygen partial pressure during deposition. The presence of Nd/Ba disorder during deposition stimulates the introduction of oxygen into the growing film. A simple model is proposed for estimation of oxygen contents in the film using structural parameters measured with XRD techniques. Studies of the post-deposition annealing process showed ordering of the Nd/Ba sub-lattice and intense oxygen in-and outdiffusion. The temperature of the post-deposition annealing step should be chosen low enough (∼400 • C) to avoid oxygen diffusion out of the NBCO film.
Journal of Superconductivity and Novel Magnetism
Pulsed laser deposition is often considered a process providing congruent transfer of target comp... more Pulsed laser deposition is often considered a process providing congruent transfer of target composition to the growing film. In fact, many different processes affect compositional preservation, starting from incongruent target ablation, to scattering on the way to the substrate, and to processes of the film formation on the substrate surface. We developed a pulsed laser deposition process trying to minimize the compositional deviations due to the scattering by the ambient gas by applying laser beam scanning across the target surface and substitution of oxygen with argon in the chamber during deposition. Transfer of elemental composition of YBa 2 Cu 3 O 7 targets with compositions varying from stoichiometric 1/2/3 ratio was tested by deposition of thin films in conditions optimal for high-temperature superconductor formation. Despite all measures, the films still show Ba,Y enrichment due to different efficiencies of scattering on the ambient gas. The Y part in the film followed well the composition of the target, but the Ba enrichment was almost constant for most of the studied target compositions, implying a crucial role of the film growth processes. The YBa 2 Cu 3 O x (YBCO) films show a layered structure, with increased density of defects in the topmost layer. We
Proceedings of SPIE - The International Society for Optical Engineering, 2004
Tilted-axes YBCO thin films: from vicinal range to step bunching. [Proceedings of SPIE 5401, 597 ... more Tilted-axes YBCO thin films: from vicinal range to step bunching. [Proceedings of SPIE 5401, 597 (2004)]. PB Mozhaev, JE Mozhaeva, IK Bdikin, T. Donchev, E. Mateev, T. Nurgaliev, CS Jacobsen, J. Bindslev Hansen, Sergei A. Zhgoon, AE Barinov. Abstract. ...
Vacuum, 2004
The results of the study (at 77 K) of electrical parameters of YBCO thin films deposited on tilte... more The results of the study (at 77 K) of electrical parameters of YBCO thin films deposited on tilted NdGaO 3 substrates using a 2-opposed-magnetron sputtering technique are reported. The films prepared on the substrates with tilt angle $31 demonstrated less surface roughness and higher critical current density. The minimum of the surface resistance (measured at 8 GHz) was observed at a smaller tilt angle of $1.51. The surface resistance demonstrated some anisotropy in the film plane, induced, possibly, by the tilted substrate. r
Physica C: Superconductivity, 2005
Thin YBa 2 Cu 3 O x (YBCO) films were deposited using DC-sputtering technique on NdGaO 3 substrat... more Thin YBa 2 Cu 3 O x (YBCO) films were deposited using DC-sputtering technique on NdGaO 3 substrates, tilted from (1 1 0) orientation by 0-26°. The structure and surface quality of the substrates were carefully characterized to obtain reliable results of thin films deposition. Structural, morphological and electrical properties of the YBCO thin films show three different ranges of inclination angle: vicinal, intermediate and high. In the vicinal range the properties of the film are generally the same as of the standard films deposited on (1 1 0) NdGaO 3 substrate. An increase of the inclination angle to the intermediate range results in a significant improvement of morphology and structural quality of the film. Best electrical parameters are measured for the films of the intermediate range also. Probable reason for such behavior is simultaneous and regular seeding of the film in the joints of facets on the substrate surface. Further increase of inclination angle leads to step bunching and oxygen out-diffusion, destroying both structural and electrical perfection of the tilted-axes YBCO film. (P.B. Mozhaev).
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Papers by Peter B Mozhaev