Precise microwave characterization of MgO substrates for HTS circuits with superconducting post dielectric resonator

Mazierska, J.; Ledenyov, Dimitri O.; Jacob, Mohan V.; Křupka, J.

doi:10.1088/0953-2048/18/1/004

Cited by 22 publications

(9 citation statements)

References 20 publications

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“…where ε MgO = 9.7 [70] is the relative permittivity of MgO, ε 0 is the vacuum permittivity, and A is the cross-sectional area of the MTJ. The first term in eq.…”

Section: B V Mtj Dependencementioning

confidence: 99%

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Deng

Liang

Gupta³

2017

Sci Rep

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Switching magnetization in a perpendicular magnetic tunnel junction (pMTJ) via voltage controlled magnetic anisotropy (VCMA) has shown the potential to markedly reduce switching energy. However, the requirement of an external magnetic field poses a critical bottleneck for its practical applications. In this work, we propose an elliptical-shaped pMTJ to eliminate the requirement of providing an external field by an additional circuit. We demonstrate that a 10 nm thick in-plane magnetized bias layer (BL) separated by a metallic spacer of 3 nm from the free layer (FL) can be engineered within the MTJ stack to provide the 50 mT bias magnetic field for switching. By conducting macrospin simulation, we find that a fast switching in 0.38 ns with energy consumption as low as 0.3 fJ at a voltage of 1.6 V can be achieved. Furthermore, we study the phase diagram of switching probability, showing that a pulse duration margin of 0.15 ns is obtained and low-voltage operation (~1 V) is favored. Finally, the MTJ scalability is considered, and it is found that scaling down may not be appealing in terms of both the energy consumption and the switching time for precession based VCMA switching.

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“…where ε MgO = 9.7 [70] is the relative permittivity of MgO, ε 0 is the vacuum permittivity, and A is the cross-sectional area of the MTJ. The first term in eq.…”

Section: B V Mtj Dependencementioning

confidence: 99%

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Deng

Liang

Gupta³

2017

Sci Rep

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“…Fillers such as BaTiO 3 possess high dielectric constant and low breakdown strength . Large differences between the dielectric constant values of ceramic fillers and the polymer matrix were shown to result in highly inhomogeneous and localized electric fields in the composites, which further reduced the breakdown strength of the composites . On the other hand, use of conductive fillers in large concentrations increases the leakage current by creating leakage paths for charge conduction .…”

Section: Introductionmentioning

confidence: 99%

“…12 Large differences between the dielectric constant values of ceramic fillers and the polymer matrix were shown to result in highly inhomogeneous and localized electric fields in the composites, which further reduced the breakdown strength of the composites. 13 On the other hand, use of conductive fillers in large concentrations increases the leakage current by creating leakage paths for charge conduction. 11 For example, silver based nanocomposites show improved piezoelectricity but at the expense of other electrical characteristics that are desirable for a high-performance device.…”

Section: ■ Introductionmentioning

confidence: 99%

Flexible and Robust Piezoelectric Polymer Nanocomposites Based Energy Harvesters

Singh

Choudhary

Garg

2018

ACS Appl. Mater. Interfaces

117

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Environment friendly, flexible, and robust sensors have attracted considerable research attention due to their potential for a wide range of devices in energy generation and harvesting, sensing, and biomedical applications. In this manuscript, we demonstrate a lead-free, solution processed flexible piezoelectric energy generator based on a nanocomposite film, consisting of MgO nanoparticles of sizes around <50 nm, embedded in poly(vinylidene difluoride) [PVDF] and its copolymer with trifluoroethylene, that is, P(VDF-TrFE) matrix. Piezoelectric, ferroelectric, and leakage current measurements made on samples with various concentrations of MgO nanoparticles revealed a dramatic improvement in these characteristics at 2 wt % MgO with nearly 50% increase in the piezoelectric coefficient as compared to pure P(VDF-TrFE), attributed to the preferred conformation of P(VDF-TrFE) chain, improved crystallinity of the P(VDF-TrFE) matrix, and uniform distribution of nanoparticles. Assessment of the interactions between -OH groups attached to MgO surface and P(VDF-TrFE), carried out using Fourier-transform infrared spectroscopy (FTIR), suggested weak van der Waals forces between -OH groups and P(VDF-TrFE) being responsible for the observed improvement. This flexible nanocomposite device exhibits superior energy harvesting performance with over two-times improvement in the voltage output (2 V) compared to device using P(VDF-TrFE) films alone. Along with superior electrical properties, nanocomposites also exhibit excellent endurance against electrical as well as mechanical fatigue, with piezoelectric coefficient remaining unchanged even after 10 000 bending cycles, supporting their suitability in flexible energy harvesting applications.

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“…in LAO) to generate inhomogeneities in the YBCO films [25]. They have a thermal expansion coefficient (≈ 1 • 10 −5 K −1 at 273 K) similar to that of YBCO, and are characterized by low dielectric constant (≈ 10) and microwave losses (loss tangent ≈ 10 −5 at 10 GHz and 90 K) [26]. It can therefore be used in devices where a good coupling with the microwave radiation is required, differently from other substrates (e.g.…”

Section: Surface Reconstruction By Temperature Annealing Of (110) Ori...mentioning

confidence: 99%

Untwinned YBa2Cu3O7−δ thin films on MgO substrates: A platform to study strain effects on the local orders in cuprates

Arpaia

Andersson

Kalaboukhov

et al. 2019

Phys. Rev. Materials

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We have grown untwinned YBa2Cu3O 7−δ (YBCO) films on (110) MgO substrates that were preannealed at high temperature in oxygen atmosphere. The annealing results in surface reconstruction with shallow facets, which induce the suppression of the YBCO twinning domains, and the preferential alignment of the CuO chains along one of the in-plane directions of the substrate. Because of the large mismatch between the in-plane lattice parameters of film and substrate, the strain induced by the MgO into the YBCO layer is strong and very peculiar. The YBCO film is compressed, with respect to the bulk, and presents a unidirectional buckling of the atomic planes, along the chains' direction, due to a deformation of the copper-oxygen octahedra. The YBCO films, which can be grown with thicknesses down to few unit cells and oxygen doping levels spanning most of the superconducting dome, are patterned into nanowires with dimensions down to 50 nm. The anisotropies due to the untwinning state are preserved in these structures; moreover, additional anisotropies appear, in ultrathin structures where strain effects become more pronounced. Such untwinned and compressively strained films can therefore be used as a platform to study the interplay between strain and the various local orders in the normal state of YBCO. * riccardo.arpaia@chalmers.se † floriana.lombardi@chalmers.se duced by the substrate. In the case of YBa 2 Cu 3 O 7−δ (YBCO), this requires the growth of films which must be untwinned, to preserve the anisotropies related to the orthorhombicity of the unit cell, and at the same time compressively strained. The growth of untwinned films, where aligned CuO chains are present throughout the sample, is not an easy task since c-axis oriented YBCO films usually grow twinned on the substrates commonly used for the deposition of cuprates. This twinning, caused by a random exchange of the in-plane a and b axis, influences the electric and magnetic properties of the films [15][16][17][18]. The best untwinned YBCO films, reported so far, have been achieved on SrTiO 3 (STO) substrates with a vicinal miscut angle, i.e. with a small misorientation, with respect to the (001) plane direction [19,20]. However, the STO substrate induces a tensile stress into the YBCO films.Here we report on the growth of untwinned YBCO films under compressive strain. We succeeded in this task, by an in-situ thermal treatment of (110) oriented MgO substrates, prior to the deposition of the YBCO thin films. The thermal treatment results in a reconstruction of the substrate surface, favoring the growth of untwinned YBCO. Moreover, the film is subject to a very peculiar compressive strain, as a result of the large mismatch between the in-plane lattice parameters of the film and the substrate: the b axis shrinks, and tilts around the normal to the MgO surface.The manuscript is organized as follows: In Section II, we start with an overview of the past results on un-arXiv:1908.02637v2 [cond-mat.supr-con]

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Precise microwave characterization of MgO substrates for HTS circuits with superconducting post dielectric resonator

Cited by 22 publications

References 20 publications

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Flexible and Robust Piezoelectric Polymer Nanocomposites Based Energy Harvesters

Untwinned YBa2Cu3O7−δ thin films on MgO substrates: A platform to study strain effects on the local orders in cuprates

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