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Dive into the research topics where Natalia V. Morozova is active.

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Featured researches published by Natalia V. Morozova.


Journal of Applied Physics | 2014

Significant enhancement of thermoelectric properties and metallization of Al-doped Mg2Si under pressure

Natalia V. Morozova; Sergey V. Ovsyannikov; Igor V. Korobeinikov; Alexander E. Karkin; Kenichi Takarabe; Yoshihisa Mori; Shigeyuki Nakamura; Vladimir V. Shchennikov

We report results of investigations of electronic transport properties and lattice dynamics of Al-doped magnesium silicide (Mg2Si) thermoelectrics at ambient and high pressures to and beyond 15 GPa. High-quality samples of Mg2Si doped with 1 at. % of Al were prepared by spark plasma sintering technique. The samples were extensively examined at ambient pressure conditions by X-ray diffraction studies, Raman spectroscopy, electrical resistivity, magnetoresistance, Hall effect, thermoelectric power (Seebeck effect), and thermal conductivity. A Kondo-like feature in the electrical resistivity curves at low temperatures indicates a possible magnetism in the samples. The absolute values of the thermopower and electrical resistivity, and Raman spectra intensity of Mg2Si:Al dramatically diminished upon room-temperature compression. The calculated thermoelectric power factor of Mg2Si:Al raised with pressure to 2–3 GPa peaking in the maximum the values as high as about 8 × 10−3 W/(K2m) and then gradually decreased ...


Applied Physics Letters | 2012

“Smart” silicon: Switching between p‐ and n‐conduction under compression

Sergey V. Ovsyannikov; Igor V. Korobeinikov; Natalia V. Morozova; A. Misiuk; Nikolai V. Abrosimov; Vladimir V. Shchennikov

We report results of thermoelectric power (Seebeck effect) and Raman spectroscopy studies on undoped and Ge-doped (1.4–2.6 at. %) Czochralski-grown silicon under high pressure to ∼17 GPa. Lattice dynamics of Si:Ge under compression resembles that in Ge-free silicon. But in contrary to undoped silicon, the electrical conduction in Si1−xGex may be reversibly (irreversibly) “switched” from p- to n-type by application of pressure of ∼0.6 GPa (∼0.8–1.5 GPa). Under pressures higher than ∼2 GPa the samples turn to a compensated state. Thus, Si:Ge being a “smart” material that opens emergent perspectives for silicon-based devices. It may be utilized, e.g., as a “smart” substrate for integrated circuits or a “smart” layer in heterostructures.


Advanced Materials | 2014

A Hard Oxide Semiconductor with A Direct and Narrow Bandgap and Switchable p–n Electrical Conduction

Sergey V. Ovsyannikov; Alexander E. Karkin; Natalia V. Morozova; Vladimir V. Shchennikov; Elena Bykova; Artem M. Abakumov; Alexander A. Tsirlin; Konstantin Glazyrin; Leonid Dubrovinsky

An oxide semiconductor (perovskite-type Mn2 O3 ) is reported which has a narrow and direct bandgap of 0.45 eV and a high Vickers hardness of 15 GPa. All the known materials with similar electronic band structures (e.g., InSb, PbTe, PbSe, PbS, and InAs) play crucial roles in the semiconductor industry. The perovskite-type Mn2 O3 described is much stronger than the above semiconductors and may find useful applications in different semiconductor devices, e.g., in IR detectors.


Applied Physics Letters | 2015

Enhanced power factor and high-pressure effects in (Bi,Sb)2(Te,Se)3 thermoelectrics

Sergey V. Ovsyannikov; Natalia V. Morozova; Igor V. Korobeinikov; Lidia N. Lukyanova; Andrey Yu. Manakov; Anna Yu. Likhacheva; A. I. Ancharov; A. P. Vokhmyanin; I. F. Berger; Oleg A. Usov; Vsevolod A. Kutasov; V.A. Kulbachinskii; Taku Okada; Vladimir V. Shchennikov

We investigated the effects of applied high pressure on thermoelectric, electric, structural, and optical properties of single-crystalline thermoelectrics, Bi2Te3, BixSb2−xTe3 (x = 0.4, 0.5, 0.6), and Bi2Te2.73Se0.27 with the high thermoelectric performance. We established that moderate pressure of about 2–4 GPa can greatly enhance the thermoelectric power factor of all of them. X-ray diffraction and Raman studies on Bi2Te3 and Bi0.5Sb1.5Te3 found anomalies at similar pressures, indicating a link between crystal structure deformation and physical properties. We speculate about possible mechanisms of the power factor enhancement and suppose that pressure/stress tuning can be an effective tool for the optimization of the thermoelectric performance.


Journal of Applied Physics | 2012

Similar behavior of thermoelectric properties of lanthanides under strong compression up to 20 GPa

Vladimir V. Shchennikov; Natalia V. Morozova; Sergey V. Ovsyannikov

We report results of investigations of thermoelectric properties of dozen of the lanthanides at ambient temperature under strong compression up to 15-20 GPa. We present data of pressure evolution of Seebeck coefficient in cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and ytterbium (Yb) and review literature data for lanthanum (La). Peculiarities detected at pressure dependencies of thermoelectric power were addressed to the known structural transitions. Therefore, thermopower values of all high-pressure phases below 20 GPa were established. Seebeck effect in different lanthanides subjected to compression demonstrated similar behavior: monotonic rising from near-zero values, ±(1-2) μV/K to magnitudes of ∼+(8-10) μV/K beyond about 5 GPa. This tendency was noticed in those rare-earth elements that follow a commonly accepted sequence of structural transformations for this group, and hence the s→d electron transfer is considered as a possible reason for this similar behavior of thermoelectric properties. Distinctive behavior of Seebeck effect in cerium and ytterbium may be related to peculiar structural phase diagrams of these elements. Possible implications from the findings of this thermoelectric study are discussed.We report results of investigations of thermoelectric properties of dozen of the lanthanides at ambient temperature under strong compression up to 15-20 GPa. We present data of pressure evolution of Seebeck coefficient in cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and ytterbium (Yb) and review literature data for lanthanum (La). Peculiarities detected at pressure dependencies of thermoelectric power were addressed to the known structural transitions. Therefore, thermopower values of all high-pressure phases below 20 GPa were established. Seebeck effect in different lanthanides subjected to compression demonstrated similar behavior: monotonic rising from near-zero values, ±(1-2) μV/K to magnitudes of ∼+(8-10) μV/K beyond about 5 GPa. This tendency was noticed in those rare-earth elements that follow a commonly accepted sequence of structural transformations for this group, and hence the s→d electron transfer is c...


Applied Physics Letters | 2011

Colossal tuning of an energy gap in Sn2P2S6 under pressure

Vladimir V. Shchennikov; Natalia V. Morozova; Iryna Tyagur; Yuriy Tyagur; Sergey V. Ovsyannikov

We report results of investigation of electrical and thermoelectric properties of Sn2P2S6 under strong compression up to 20 GPa. An “insulator-metal”(I-M)-type transition was discovered by a monotonic and reversible lowering of electrical resistivity by 9–10 orders. The energy gap (Eg = 2.3 eV) was estimated to decrease to ∼0.25–0.3 eV at 20 GPa. X-ray diffraction and Raman studies on samples recovered from the high pressure experiments confirm a conservation of the original monoclinic lattice. Thus, a colossal “band-gap engineering” potential is revealed in this optical material. Sn2P2S6 is a potential candidate for emergent multi-functional switches, between transparent “insulator” state and conducting state with magneto-dependent properties.


Superconductor Science and Technology | 2015

Electronic transport properties of MFe2As2 (M = Ca, Eu, Sr) at ambient and high pressures up to 20 GPa

Natalia V. Morozova; Alexander E. Karkin; Sergey V. Ovsyannikov; Yuliya A Umerova; Vladimir V. Shchennikov; R Mittal; A. Thamizhavel

We experimentally investigated the electronic transport properties of four iron pnictide crystals, namely, EuFe2As2, SrFe2As2, and CaFe2As2 parent compounds, and superconducting CaFe1.94Co0.06As2 at ambient and high pressures up to 20 GPa. At ambient pressure we examined the electrical resistivity, Hall and magnetoresistance effects of the samples in a temperature range from 1.5 to 380 K in high magnetic fields up to 13.6 T. In this work we carried out the first simultaneous investigations of the in-plane and out-of-plane Hall coefficients, and found new peculiarities of the low-temperature magnetic and structural transitions that occur in these materials. In addition, the Hall coefficient data suggested that the parent compounds are semimetals with a multi-band conductivity that includes hole-type and electron-type bands. We measured the pressure dependence of the thermoelectric power (the Seebeck effect) of these samples up to 20 GPa, i.e. across the known phase transition from the tetragonal to the collapsed tetragonal lattice. The high-pressure behavior of the thermopower of EuFe2As2 and CaFe2As2 showing the p-n sign inversions was consistent with the semimetal model described above. By means of thermopower, we found in single-crystalline CaFe2As2 direct evidence of the band structure crossover related to the formation of As–As bonds along the c-axis on the tetragonal → collapsed tetragonal phase transition near 2 GPa. We showed that this feature is distinctly observable only in high-quality samples, and already for re-pressurization cycles this crossover was strongly smeared because of the moderate deterioration of the sample. We also demonstrated by means of thermopower that the band structure crossover that should accompany the tetragonal → collapsed tetragonal phase transition in EuFe2As2 near 8 GPa is hardly visible even in high-quality single crystals. This behavior may be related to a gradual valence change of the Eu ions under pressure that leads to an injection of free electrons and the steady shift of the conduction to n-type.


Journal of Applied Physics | 2013

Raman spectroscopy of ferroelectric Sn2P2S6 under high pressure up to 40 GPa: Phase transitions and metallization

Sergey V. Ovsyannikov; Huiyang Gou; Natalia V. Morozova; Iryna Tyagur; Yuriy Tyagur; Vladimir V. Shchennikov

We report results of a Raman spectroscopy study of non-oxide ferroelectric tin-hypothiodiphosphate (Sn2P2S6) at ambient temperature under application of high pressure up to 40 GPa. Pressure evolution of the Raman spectra revealed several different compression regimes that are most likely related to phase transitions, with boundaries near <1, ∼5–7, ∼16–19, ∼26–29, and ∼39 GPa. Above 39 GPa, the Raman signal disappeared. Pronounced softening in some phonon modes prior to these crossovers also suggested that these features are related to structural phase transitions. In optical absorption spectroscopy, we confirmed the wide semiconductor band gap Eg of Sn2P2S6, and in particular, found indirect gap of Eg = 2.26 eV and direct one of Eg = 2.42 eV. In visual examinations, we observed that the sample color gradually changed with pressure from yellow to orange, red, and then to opaque. Eventually, at the maximal pressure achieved in our study, the sample demonstrated a metallic luster. Hence, the metallization at...


Journal of Applied Physics | 2015

Features and regularities in behavior of thermoelectric properties of rare-earth, transition, and other metals under high pressure up to 20 GPa

Natalia V. Morozova; Vladimir V. Shchennikov; Sergey V. Ovsyannikov

We report results of systematic investigations of the thermoelectric properties of a number of rare-earth metals, transition metals, and other metals under high pressure up to 20 GPa at room temperature. We studied an effect of applied pressure on the Seebeck effect of scandium (Sc), yttrium (Y), lanthanum (La), europium (Eu), ytterbium (Yb), iron (Fe), manganese (Mn), chromium (Cr), gold (Au), tin (Sn), and CeNi alloy. We found that the high-pressure behavior of the thermopower of three rare-earth metals, namely, Sc, Y, and La, follows a general trend that has been established earlier in lanthanides, and addressed to a s → d electron transfer. Europium and ytterbium, on the contrary, showed a peculiar high-pressure behavior of the thermopower with peaks at near 0.7–1 GPa for Eu and 1.7–2.5 GPa for Yb. Chromium, manganese, and tin demonstrated a gradual and pronounced lowering of the absolute value of the thermopower with pressure. Above 9–11 GPa, the Seebeck coefficients of Mn and Sn were inverted, from ...


Scientific Reports | 2017

Dramatic Changes in Thermoelectric Power of Germanium under Pressure: Printing n–p Junctions by Applied Stress

Igor V. Korobeinikov; Natalia V. Morozova; Vladimir V. Shchennikov; Sergey V. Ovsyannikov

Controlled tuning the electrical, optical, magnetic, mechanical and other characteristics of the leading semiconducting materials is one of the primary technological challenges. Here, we demonstrate that the electronic transport properties of conventional single-crystalline wafers of germanium may be dramatically tuned by application of moderate pressures. We investigated the thermoelectric power (Seebeck coefficient) of p– and n–type germanium under high pressure to 20 GPa. We established that an applied pressure of several GPa drastically shifts the electrical conduction to p–type. The p–type conduction is conserved across the semiconductor-metal phase transition at near 10 GPa. Upon pressure releasing, germanium transformed to a metastable st12 phase (Ge-III) with n–type semiconducting conductivity. We proposed that the unusual electronic properties of germanium in the original cubic-diamond-structured phase could result from a splitting of the “heavy” and “light” holes bands, and a related charge transfer between them. We suggested new innovative applications of germanium, e.g., in technologies of printing of n–p and n–p–n junctions by applied stress. Thus, our work has uncovered a new face of germanium as a ‘smart’ material.

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I. F. Berger

Russian Academy of Sciences

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