The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Y.d. Zheng - One of the best experts on this subject based on the ideXlab platform.
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A thermodynamic model and estimation of the experimental value of Spontaneous Polarization in a wurtzite GaN
Applied Physics Letters, 2009Co-Authors: Wensheng Yan, Zhang Rong, Xiangqian Xiu, Zili Xie, Peigao Han, Y. Shi, Peng Chen, Y.d. ZhengAbstract:Determining the Spontaneous Polarization is a fundamental problem in the III-nitride field. However the experimental value of the Spontaneous Polarization has not yet been reported. In this study, a thermodynamic model is proposed to investigate the Spontaneous Polarization of GaN from the GaN high-pressure phase transition. Total macroscopic Polarization is directly expressed as coefficients in expansion, and these coefficients are found to be conducted in experiments. The experimental value of the Spontaneous Polarization of GaN is estimated to be around −0.022 C/m2.
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Temperature dependence of the pyroelectric coefficient and the Spontaneous Polarization of AlN
Applied Physics Letters, 2007Co-Authors: Wensheng Yan, Zhang Rong, Xiangqian Xiu, Zili Xie, Peigao Han, R. L. Jiang, Y. Shi, Y.d. ZhengAbstract:Using the Debye model and existing experimental data of the pyroelectric coefficient of AlN, the temperature dependence of the pyroelectric coefficient as well as the Spontaneous Polarization of AlN is calculated over a wide temperature range from 0to1000K. The pyroelectric coefficient is proportional to T3 at low temperature and increases acutely from 0 to around 400K, and then increases gently from 400to1000K. It makes AlN uniquely suitable for application in high temperature pyroelectric sensors. The Spontaneous Polarization of AlN changes a little from 0to1000K, which indicates that the features of III-nitrides based devices will hardly be degraded by the change of the Spontaneous Polarization.
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Phenomenological model for the Spontaneous Polarization of GaN
Applied Physics Letters, 2007Co-Authors: Wensheng Yan, Zhang Rong, Xiangqian Xiu, Zili Xie, Peigao Han, R. L. Jiang, Y. Shi, Y.d. ZhengAbstract:A phenomenological model is presented to determine the experimental value of the Spontaneous Polarization of GaN. The expression of the Spontaneous Polarization at room temperature is obtained. The electrostrictive coefficient M33 of a wurtzite GaN film is used to evaluate the experimental value of the Spontaneous Polarization of GaN. The exact experimental value of the Spontaneous Polarization of GaN can be obtained as long as the electrostrictive coefficient M33 of the single crystal zinc blende GaN film is measured. The phenomenological model can also be used to determine the experimental values of the Spontaneous Polarization in other III-V nitrides, AlN and InN.
Masaru Miyayama - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Spontaneous Polarization in superlattice-structured Bi4Ti3O12–BaBi4Ti4O15 single crystals
Applied Physics Letters, 2005Co-Authors: Tomo Kobayashi, Yuji Noguchi, Masaru MiyayamaAbstract:Superlattice-structured ferroelectric single crystals composed of Bi4Ti3O12 (BiT) and BaBi4Ti4O15 (BBTi) have been reported to show a large Spontaneous Polarization as well as a sufficient insulating property. X-ray diffraction and transmission electron microscopy observations of the crystals revealed a superlattice structure with alternate stacking of the BiT and the BBTi layers. The Curie temperature (TC) of the BiT–BBTi crystals was about 540 °C, which was intermediate between those of BiT (675 °C) and BBTi (410 °C). Polarization measurements of the BiT–BBTi crystals along the a(b) axis demonstrate that the Spontaneous Polarization was 52μC∕cm2, which is larger than those of the BiT and BBTi crystals.
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enhanced Spontaneous Polarization in superlattice structured bi4ti3o12 babi4ti4o15 single crystals
Applied Physics Letters, 2005Co-Authors: Tomo Kobayashi, Yuji Noguchi, Masaru MiyayamaAbstract:Superlattice-structured ferroelectric single crystals composed of Bi4Ti3O12 (BiT) and BaBi4Ti4O15 (BBTi) have been reported to show a large Spontaneous Polarization as well as a sufficient insulating property. X-ray diffraction and transmission electron microscopy observations of the crystals revealed a superlattice structure with alternate stacking of the BiT and the BBTi layers. The Curie temperature (TC) of the BiT–BBTi crystals was about 540 °C, which was intermediate between those of BiT (675 °C) and BBTi (410 °C). Polarization measurements of the BiT–BBTi crystals along the a(b) axis demonstrate that the Spontaneous Polarization was 52μC∕cm2, which is larger than those of the BiT and BBTi crystals.
Wensheng Yan - One of the best experts on this subject based on the ideXlab platform.
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A thermodynamic model and estimation of the experimental value of Spontaneous Polarization in a wurtzite GaN
Applied Physics Letters, 2009Co-Authors: Wensheng Yan, Zhang Rong, Xiangqian Xiu, Zili Xie, Peigao Han, Y. Shi, Peng Chen, Y.d. ZhengAbstract:Determining the Spontaneous Polarization is a fundamental problem in the III-nitride field. However the experimental value of the Spontaneous Polarization has not yet been reported. In this study, a thermodynamic model is proposed to investigate the Spontaneous Polarization of GaN from the GaN high-pressure phase transition. Total macroscopic Polarization is directly expressed as coefficients in expansion, and these coefficients are found to be conducted in experiments. The experimental value of the Spontaneous Polarization of GaN is estimated to be around −0.022 C/m2.
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Temperature dependence of the pyroelectric coefficient and the Spontaneous Polarization of AlN
Applied Physics Letters, 2007Co-Authors: Wensheng Yan, Zhang Rong, Xiangqian Xiu, Zili Xie, Peigao Han, R. L. Jiang, Y. Shi, Y.d. ZhengAbstract:Using the Debye model and existing experimental data of the pyroelectric coefficient of AlN, the temperature dependence of the pyroelectric coefficient as well as the Spontaneous Polarization of AlN is calculated over a wide temperature range from 0to1000K. The pyroelectric coefficient is proportional to T3 at low temperature and increases acutely from 0 to around 400K, and then increases gently from 400to1000K. It makes AlN uniquely suitable for application in high temperature pyroelectric sensors. The Spontaneous Polarization of AlN changes a little from 0to1000K, which indicates that the features of III-nitrides based devices will hardly be degraded by the change of the Spontaneous Polarization.
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Phenomenological model for the Spontaneous Polarization of GaN
Applied Physics Letters, 2007Co-Authors: Wensheng Yan, Zhang Rong, Xiangqian Xiu, Zili Xie, Peigao Han, R. L. Jiang, Y. Shi, Y.d. ZhengAbstract:A phenomenological model is presented to determine the experimental value of the Spontaneous Polarization of GaN. The expression of the Spontaneous Polarization at room temperature is obtained. The electrostrictive coefficient M33 of a wurtzite GaN film is used to evaluate the experimental value of the Spontaneous Polarization of GaN. The exact experimental value of the Spontaneous Polarization of GaN can be obtained as long as the electrostrictive coefficient M33 of the single crystal zinc blende GaN film is measured. The phenomenological model can also be used to determine the experimental values of the Spontaneous Polarization in other III-V nitrides, AlN and InN.
S. Yu. Davydov - One of the best experts on this subject based on the ideXlab platform.
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On the effect of the Spontaneous Polarization of a SiC substrate on a buffer layer and quasi-free single-sheet graphene
Semiconductors, 2012Co-Authors: S. Yu. DavydovAbstract:The study is concerned with two problems: (i) the influence of the Spontaneous Polarization of a SiC substrate on the binding energy of silicon and carbon atoms of the substrate with carbon atoms of the buffer layer and (ii) the role of the Spontaneous Polarization of the SiC substrate in the doping of quasi-free single-sheet graphene. In case (i), it is shown that Spontaneous Polarization has practically no effect on the substrate-(buffer layer) binding energy. In case (ii), Spontaneous Polarization has a profound qualitative effect, only if the Fermi level in the system is almost coincident with the Dirac point of graphene. All estimates are obtained in the context of simple models. The 6H-SiC {0001} and 4H-SiC {0001} polytypes are studied as the substrates.
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On the possibility of the experimental determination of Spontaneous Polarization for silicon carbide polytypes
Semiconductors, 2012Co-Authors: S. Yu. Davydov, A. A. Lebedev, O. V. PosrednikAbstract:A NH-SiC/3C-SiC heterojunction and a heterostructure of the NH-SiC/3C-SiC/NH-SiC type (N = 2, 4, 6, 8), fabricated from silicon carbide polytypes, are considered. Two possibilities are analyzed for the heterojunctions, in which a Si or a C plane is the contact plane of the NH polytype. In this case, the energies of quasi-local levels in the quantum wells at the interface will be different. With the difference of these energies measured, it is possible to determine the Spontaneous Polarization Psp inherent in the NH polytype. In the presence of a Spontaneous Polarization field, the quasi-local levels in the left- and right-hand quantum wells of the heterostructure have different energies. It is shown that, if the heterostructure is placed in an external electric field, it is possible to determine the magnitude of the Spontaneous Polarization by calculating the difference between the energies of these levels. Experimental ways to find Psp by using the suggested theoretical scenario are discussed.
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Energy features induced by Spontaneous Polarization in the NH/3C/NH-SiC heterostructure: A general treatment
Physics of the Solid State, 2011Co-Authors: S. Yu. Davydov, O. V. PosrednikAbstract:The effect of Spontaneous Polarization of hexagonal regions of a trilayer NH/3C/NH heterostructure on the relative position of the bands has been considered within the model previously proposed for the description of the NH/3C heterojunction. Considerable attention has been focused on the study of the effect of Spontaneous Polarization and thickness of the 3C region on the energy characteristics of the quantum wells formed near heterojunctions.
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Estimates of the Spontaneous Polarization in silicon carbide
Physics of the Solid State, 2007Co-Authors: S. Yu. Davydov, A. V. TroshinAbstract:Various approaches to calculating the Spontaneous Polarization P sp for different polytypes of silicon carbide are discussed. Our estimates combined with data reported by other authors reveal a considerable scatter in the values of P sp for the 2 H -SiC polytype (from -1.11 to -4.32 × 10 -2 C/m 2 ). The need for further studies is stressed.
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Role of Spontaneous Polarization in formation of heterojunctions from silicon carbide polytypes
Semiconductors, 2007Co-Authors: S. Yu. Davydov, A. A. Lebedev, A. V. TroshinAbstract:Solution of the Poisson equation is analyzed in terms of the model of a completely depleted contact layer for a heterojunction having as one of its components a noncubic silicon carbide polytype that exhibits a Spontaneous Polarization Psp. It is shown that consideration of Psp leads to broadening of the space charge regions. It is demonstrated that an isotype p-p junction with a quantum well in the valence band of the 3C polytype at the interface with the H-SiC polytype can serve as a model object for studies of the effect exerted by the Spontaneous Polarization on the properties of SiC heterojunctions. The possibility of a noticeable effect of Psp on the ground-state energy of an electron in the well is demonstrated for the model with a triangular potential well.
L. Bata - One of the best experts on this subject based on the ideXlab platform.
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Chiral smectic side-chain copolymers—2. Pyroelectric effect and Spontaneous Polarization
European Polymer Journal, 1992Co-Authors: Mikhail V. Kozlovsky, S.g. Kononov, L.m. Blinov, Katalin Fodor-csorba, L. BataAbstract:Abstract Temperature dependences of pyroelectric coefficient, Spontaneous Polarization and relaxation time have been measured for a series of ferroelectric liquid crystalline copolymers.
