Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/...Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the Co layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a corresponding lateral anisotropy gradient in the Co layer,correlating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.展开更多
Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP),of much interest owing to its high ionic conductivity,superior air stability,and low cost,has been regarded as one of the most promising solid-state electrolytes for next-gen...Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP),of much interest owing to its high ionic conductivity,superior air stability,and low cost,has been regarded as one of the most promising solid-state electrolytes for next-generation solid-state lithium batteries(SSLBs).Unfortunately,the commercialization of SSLBs is still impeded by severe interfacial issues,such as high interfacial impedance and poor chemical stability.Herein,we proposed a simple and convenient in-situ approach to constructing a tight and robust interface between the Li anode and LATP electrolyte via a SnO_(2)gradient buffer layer.It is firmly attached to the surface of LATP pellets due to the volume expansion of SnO_(2)when in-situ reacting with Li metal,and thus effectively alleviates the physical contact loosening during cycling,as confirmed by the mitigated impedance rising.Meanwhile,the as-formed SnO_(2)/Sn/LixSn gradient buffer layer with low electronic conductivity successfully protects the LATP electrolyte surface from erosion by the Li metal anode.Additionally,the LixSn alloy formed at the Li surface can effectively regulate uniform lithium deposition and suppress Li dendrite growth.Therefore,this work paves a new way to simultaneously address the chemical instability and poor physical contact of LATP with Li metal in developing low-cost and highly stable SSLBs.展开更多
The CeO2 and Y2O3 buffer layers were deposited on the cube textured metallic Ni substrates by using reactive magnetron sputtering. Ar/H2 mixed atmosphere, which is used as pre-depositing gas, can effectively inhibit t...The CeO2 and Y2O3 buffer layers were deposited on the cube textured metallic Ni substrates by using reactive magnetron sputtering. Ar/H2 mixed atmosphere, which is used as pre-depositing gas, can effectively inhibit the formation of NiO. In addition, the linear relationship between pre-depositing time and total depositing time is required to ensure the epitaxial growth of the films. The growth conditions of CeO2 and Y2O3 were comparatively studied, and it is found that the windows of substrate temperatures and pressures for CeO2 films are wider than that for Y2O3 films.展开更多
The buffer layer CeO2 films were grown on cube textured metallic Ni substrates by using reactive magnetrun sputtering. Ar/H2 mixed atmosphere, which effectively inhibited the formation of NiO, was used as pre-depositi...The buffer layer CeO2 films were grown on cube textured metallic Ni substrates by using reactive magnetrun sputtering. Ar/H2 mixed atmosphere, which effectively inhibited the formation of NiO, was used as pre-depositing gas before CeO2 films were grown in Ar and 02. At 700 ℃ under the total pressure of 26 Pa,the pure c-axis orientation tilm was obtained. X-ray θ-2θscan, pole figure and φ-scan were used to observe the microstructure of the buffer layer. The resuits show that CeO2 film has strong cube texture and the FWHM is 9°. In addition, the CeO2 film is dense and crack-free.展开更多
VO_2 thin films were grown on silicon substrates using Al_2O_3 thin films as the buffer layers. Compared with direct deposition on silicon, VO_2 thin films deposited on Al_2O_3 buffer layers experience a significant i...VO_2 thin films were grown on silicon substrates using Al_2O_3 thin films as the buffer layers. Compared with direct deposition on silicon, VO_2 thin films deposited on Al_2O_3 buffer layers experience a significant improvement in their microstructures and physical properties. By optimizing the growth conditions, the resistance of VO_2 thin films can change by four orders of magnitude with a reduced thermal hysteresis of 4 °C at the phase transition temperature. The electrically driven phase transformation was measured in Pt/Si/Al_2O_3/VO_2/Au heterostructures. The introduction of a buffer layer reduces the leakage current and Joule heating during electrically driven phase transitions. The C–V measurement result indicates that the phase transformation of VO_2 thin films can be induced by an electrical field.展开更多
Ba0.6Sr0.4TiO3 (BST) thin films with and without HfO 2 buffer layer were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Dependences of HfO 2 thickness on the dielectric property and leakage curre...Ba0.6Sr0.4TiO3 (BST) thin films with and without HfO 2 buffer layer were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Dependences of HfO 2 thickness on the dielectric property and leakage current of BST thin films were focused. The dielectric constant of BST thin films increased and then decreased with the increase of HfO 2 thickness, while the dielectric relaxation was gradually improved. The loss tangent and leakage current under positive bias decreased with the HfO 2 thickness increasing. The leakage current analysis based on the Schottky emission indicated an improvement of the BST/Pt interface with HfO 2 buffer layer. The loss tangent, tunability and figure of merit of optimized HfO 2 buffered BST thin film achieved 0.009 8, 21.91% (E max = 200 kV/cm), 22.40 at 10 6 Hz, respectively.展开更多
Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films. In this paper, Co films with different thickness of Co Si2 buffer layers were grown on Si(001) substrates. In order to investi...Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films. In this paper, Co films with different thickness of Co Si2 buffer layers were grown on Si(001) substrates. In order to investigate morphology, structure,and magnetic properties of films, scanning tunneling microscope(STM), low energy electron diffraction(LEED), high resolution transmission electron microscopy(HRTEM), and surface magneto-optical Kerr effect(SMOKE) were used. The results show that the crystal quality and magnetic anisotropies of the Co films are strongly affected by the thickness of Co Si2 buffer layers. Few Co Si2 monolayers can prevent the interdiffusion of Si substrate and Co film and enhance the Co film quality. Furthermore, the in-plane magnetic anisotropy of Co film with optimal buffer layer shows four-fold symmetry and exhibits the two-jumps of magnetization reversal process, which is the typical phenomenon in cubic(001) films.展开更多
Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition (PLD) under the same conditions have been studied. Of them, one group is of CeO2 films, which...Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition (PLD) under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel (SS) tapes coated by IBAD-YSZ (IBAD-YSZ/SS), and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density (Jc) of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50 nm. The surface morphologies of the two groups of samples are examined by SEM.展开更多
Porous SiO_(2)film has been widely studied due to its extensive applications in many fields.This paper presents a newly produced porous SiO_(2)film made by traditional sol-gel method.Bare Si and Si with SiO_(2)buffer ...Porous SiO_(2)film has been widely studied due to its extensive applications in many fields.This paper presents a newly produced porous SiO_(2)film made by traditional sol-gel method.Bare Si and Si with SiO_(2)buffer layer were used as substrate.The SiO_(2)buffer layer was 500 nm in thickness and was grown by thermal oxidization.The structural properties of SiO_(2)aerogel films spincoated on both materials were observed by optical microscope(OM)and scanning electron microscope(SEM).Results reveal that the surface of SiO_(2)aerogel films on bare Si is rough and discontinuous.While flat and smooth surface is observed on sample with SiO_(2)buffer layer.This indicates that by inserting SiO_(2)buffer layer,the structural property of SiO_(2)aerogel film deposited on Si is improved.展开更多
We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2+] on particle size and photoluminescence (PL) of ZnS:Mn^2+ nanocrystMs. By changing the [S^2-]/[Zn^2+] ratio from 0.6 (Zn-rich) to 2.0 (S-...We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2+] on particle size and photoluminescence (PL) of ZnS:Mn^2+ nanocrystMs. By changing the [S^2-]/[Zn^2+] ratio from 0.6 (Zn-rich) to 2.0 (S-rich), the particle size increases from nearly 2. 7nm to about 4.Ohm. The increase in the ratio of [S^2-]/[Zn^2+] cadses a decrease of PL emission intensity of ZnS host while a distinct increase of Mn^2+ emission. The maximum intensity for the luminescence of Mn^2+ emission is observed at the ratio of [S^2-]/[Zn^2+] ≈ 1.5. The possible mechanism for the results is discussed by filling of S^2- vacancies and the increase of Mn^2+ ions incorporated into ZnS lattices.展开更多
Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices a...Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.展开更多
Lead-free piezoelectric ceramics 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 + xmol% Co3+ (BNBT-Co, x = 0-8) are prepared by the solid state reaction method. Effects of the amount of Co^3+ on the electrical properties and ...Lead-free piezoelectric ceramics 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 + xmol% Co3+ (BNBT-Co, x = 0-8) are prepared by the solid state reaction method. Effects of the amount of Co^3+ on the electrical properties and phase transition are studied. The results indicate that the addition of Co^3+ enhances the mechanical quality factor Q^3+ significantly, whereas the dissipation factor tanδ has a minimum value at x = 3.5. Meanwhile, addition of Co^3+ leads to small decreases of piezoelectric constant d33, and planar electromechanical coupling kp. The present 0.92(Bio.aNao.5) TiO3-0.08BaTiO3+3.5 moi% Co^3+ ceramics exhibit good performance with mechanical quality factor Qm = 910, piezoelectric constant d33 = 106pC/N, planar electromechanical coupling kp =10% and dissipation factor tanδ = 1.1% at 1 kHz. Saturated polarization hysteresis loops have been obtained for BNBT-Co ceramics. Two dielectric peaks at depolarization temperature Td and Tm appear in the curves of ε33^T vs temperature for the pure BNBT ceramics. However, the first dielectric peak Td disappears after the addition of Co^3+, which means that the transition from ferroelectric to antiferroelectric phase has been eliminated.展开更多
The subband energy and lasing wavelength of compressively strained triangular Ino.53Ga0.47As/InAs quantum well are calculated and compared with the conventional rectangular ones with the same strain contents. The stra...The subband energy and lasing wavelength of compressively strained triangular Ino.53Ga0.47As/InAs quantum well are calculated and compared with the conventional rectangular ones with the same strain contents. The strain compensation using Al0.33In0.36Ga0.31As barrier is introduced. The results show that lasing wavelength can be extended dramatically to beyond 2.8μm by changing the energy band from the conventional rectangular shape to a triangular one, the realization of such a structure using molecular beam epitaxy technology is also discussed.展开更多
Based on the mechanism of injection, transport and recombination of the charge carriers, we develop a model to calculate the delay time of electroluminescence (EL) from bilayer organic light emitting diodes. The eff...Based on the mechanism of injection, transport and recombination of the charge carriers, we develop a model to calculate the delay time of electroluminescence (EL) from bilayer organic light emitting diodes. The effect of injection, transport and recombination processes on the EL delay time is discussed, and the relationship between the internal interface barrier and the recombination time is revealed. "]~he results show that the EL delay time is dominated by the recombination process at lower applied voltage and by the transport process at higher applied voltage. When the internal interface barrier varies from 0.15 eV to 0.3 eV, the recombination delay time increases rapidly~ while the internal interface barrier exceeds about 0.3eV~ the dependence of the recombination delay time on applied voltage is almost undiversified, which may serve as a guideline for designing of a high-speed EL response device.展开更多
Sr1-xLa2x/3Bi2Nb20O (0 ≤ x ≤0.2) ceramic samples are prepared by the solid-state reaction method. Their structure, dielectric and ferroelectric properties are investigated. The incorporation of La^3+ improves the...Sr1-xLa2x/3Bi2Nb20O (0 ≤ x ≤0.2) ceramic samples are prepared by the solid-state reaction method. Their structure, dielectric and ferroelectric properties are investigated. The incorporation of La^3+ improves the den- sification and decreases the grain size of the ceramics without changing the crystal structure. The remanent polarization 2PT increases with increasing La content and reaches a maximum value of 22.8μC/cm^2 at x = 0.125, which is approximately 60% larger than that of pure SrBi2Nb2O9. The Curie temperature keeps almost unchanged at a value of about 440℃. The relationship between doping and the ferroeleetrie and dielectric properties are discussed.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.12274108)the Natural Science Foundation of Zhejiang Province,China (Grant Nos.LY23A040008 and LY23A040008)the Basic Scientific Research Project of Wenzhou,China (Grant No.G20220025)。
文摘Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the Co layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a corresponding lateral anisotropy gradient in the Co layer,correlating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.
基金financially supported by the China Postdoctoral Science Foundation(2021M700396)the National Natural Science Foundation of China(52102206)the research grants from the National Research Foundation(2022K1A3A1A20014496 and 2022R1F1A1074707)funded by the government of the Republic of Korea。
文摘Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP),of much interest owing to its high ionic conductivity,superior air stability,and low cost,has been regarded as one of the most promising solid-state electrolytes for next-generation solid-state lithium batteries(SSLBs).Unfortunately,the commercialization of SSLBs is still impeded by severe interfacial issues,such as high interfacial impedance and poor chemical stability.Herein,we proposed a simple and convenient in-situ approach to constructing a tight and robust interface between the Li anode and LATP electrolyte via a SnO_(2)gradient buffer layer.It is firmly attached to the surface of LATP pellets due to the volume expansion of SnO_(2)when in-situ reacting with Li metal,and thus effectively alleviates the physical contact loosening during cycling,as confirmed by the mitigated impedance rising.Meanwhile,the as-formed SnO_(2)/Sn/LixSn gradient buffer layer with low electronic conductivity successfully protects the LATP electrolyte surface from erosion by the Li metal anode.Additionally,the LixSn alloy formed at the Li surface can effectively regulate uniform lithium deposition and suppress Li dendrite growth.Therefore,this work paves a new way to simultaneously address the chemical instability and poor physical contact of LATP with Li metal in developing low-cost and highly stable SSLBs.
文摘The CeO2 and Y2O3 buffer layers were deposited on the cube textured metallic Ni substrates by using reactive magnetron sputtering. Ar/H2 mixed atmosphere, which is used as pre-depositing gas, can effectively inhibit the formation of NiO. In addition, the linear relationship between pre-depositing time and total depositing time is required to ensure the epitaxial growth of the films. The growth conditions of CeO2 and Y2O3 were comparatively studied, and it is found that the windows of substrate temperatures and pressures for CeO2 films are wider than that for Y2O3 films.
文摘The buffer layer CeO2 films were grown on cube textured metallic Ni substrates by using reactive magnetrun sputtering. Ar/H2 mixed atmosphere, which effectively inhibited the formation of NiO, was used as pre-depositing gas before CeO2 films were grown in Ar and 02. At 700 ℃ under the total pressure of 26 Pa,the pure c-axis orientation tilm was obtained. X-ray θ-2θscan, pole figure and φ-scan were used to observe the microstructure of the buffer layer. The resuits show that CeO2 film has strong cube texture and the FWHM is 9°. In addition, the CeO2 film is dense and crack-free.
基金financially supported by the National Natural Science Foundation of China (Nos. 51401046, 51572042, 61131005, 61021061, and 61271037)International Cooperation Projects (Nos. 2013HH0003 and 2015DFR50870)+3 种基金the 111 Project (No. B13042)the Sichuan Province S&T program (Nos. 2014GZ0003, 2015GZ0091, and 2015GZ0069)Fundamental Research Funds for the Central Universitiesthe start-up fund from the University of Electronic Science and Technology of China
文摘VO_2 thin films were grown on silicon substrates using Al_2O_3 thin films as the buffer layers. Compared with direct deposition on silicon, VO_2 thin films deposited on Al_2O_3 buffer layers experience a significant improvement in their microstructures and physical properties. By optimizing the growth conditions, the resistance of VO_2 thin films can change by four orders of magnitude with a reduced thermal hysteresis of 4 °C at the phase transition temperature. The electrically driven phase transformation was measured in Pt/Si/Al_2O_3/VO_2/Au heterostructures. The introduction of a buffer layer reduces the leakage current and Joule heating during electrically driven phase transitions. The C–V measurement result indicates that the phase transformation of VO_2 thin films can be induced by an electrical field.
基金Project supported by the Foundation of the Education Commission of Shanghai Municipality (Grant Nos.07ZZ14, 08SG41)the National Natural Science Foundation of China (Grant No.50711130241)the Shanghai Rising Star Program (GrantNo.08QH14008)
文摘Ba0.6Sr0.4TiO3 (BST) thin films with and without HfO 2 buffer layer were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Dependences of HfO 2 thickness on the dielectric property and leakage current of BST thin films were focused. The dielectric constant of BST thin films increased and then decreased with the increase of HfO 2 thickness, while the dielectric relaxation was gradually improved. The loss tangent and leakage current under positive bias decreased with the HfO 2 thickness increasing. The leakage current analysis based on the Schottky emission indicated an improvement of the BST/Pt interface with HfO 2 buffer layer. The loss tangent, tunability and figure of merit of optimized HfO 2 buffered BST thin film achieved 0.009 8, 21.91% (E max = 200 kV/cm), 22.40 at 10 6 Hz, respectively.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB921801 and 2012CB933102)the National Natural Science Foundation of China(Grant Nos.11374350,11034004,11274361,and 11274033)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20131102130005)
文摘Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films. In this paper, Co films with different thickness of Co Si2 buffer layers were grown on Si(001) substrates. In order to investigate morphology, structure,and magnetic properties of films, scanning tunneling microscope(STM), low energy electron diffraction(LEED), high resolution transmission electron microscopy(HRTEM), and surface magneto-optical Kerr effect(SMOKE) were used. The results show that the crystal quality and magnetic anisotropies of the Co films are strongly affected by the thickness of Co Si2 buffer layers. Few Co Si2 monolayers can prevent the interdiffusion of Si substrate and Co film and enhance the Co film quality. Furthermore, the in-plane magnetic anisotropy of Co film with optimal buffer layer shows four-fold symmetry and exhibits the two-jumps of magnetization reversal process, which is the typical phenomenon in cubic(001) films.
文摘Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition (PLD) under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel (SS) tapes coated by IBAD-YSZ (IBAD-YSZ/SS), and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density (Jc) of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50 nm. The surface morphologies of the two groups of samples are examined by SEM.
基金financially supported by the National Natural Science Foundation of China(No.51102037)the Fundamental Research Funds for the Central Universities from UESTC(Nos.ZYGX2010J030 and ZYGX2011J023)。
文摘Porous SiO_(2)film has been widely studied due to its extensive applications in many fields.This paper presents a newly produced porous SiO_(2)film made by traditional sol-gel method.Bare Si and Si with SiO_(2)buffer layer were used as substrate.The SiO_(2)buffer layer was 500 nm in thickness and was grown by thermal oxidization.The structural properties of SiO_(2)aerogel films spincoated on both materials were observed by optical microscope(OM)and scanning electron microscope(SEM).Results reveal that the surface of SiO_(2)aerogel films on bare Si is rough and discontinuous.While flat and smooth surface is observed on sample with SiO_(2)buffer layer.This indicates that by inserting SiO_(2)buffer layer,the structural property of SiO_(2)aerogel film deposited on Si is improved.
基金Supported by the National Natural Science Foundation of China under Grant No 10674074, and the Tianjin Natural Science Foundation under Grant Nos 06TXTJJC14601 and 07JCYBJC06400.
文摘We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2+] on particle size and photoluminescence (PL) of ZnS:Mn^2+ nanocrystMs. By changing the [S^2-]/[Zn^2+] ratio from 0.6 (Zn-rich) to 2.0 (S-rich), the particle size increases from nearly 2. 7nm to about 4.Ohm. The increase in the ratio of [S^2-]/[Zn^2+] cadses a decrease of PL emission intensity of ZnS host while a distinct increase of Mn^2+ emission. The maximum intensity for the luminescence of Mn^2+ emission is observed at the ratio of [S^2-]/[Zn^2+] ≈ 1.5. The possible mechanism for the results is discussed by filling of S^2- vacancies and the increase of Mn^2+ ions incorporated into ZnS lattices.
文摘Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.
基金Supported by the National Natural Science Foundation of China under No 50562002, the New Century Excellent Talents in University (NCET-06-0576), the Key Industrial Project of Jiangxi Provincial Department of Science and Technology [2005]52, Jiangxi Provincial Department of Education [2005]217, the Natural Science Foundation of Jiangxi Province (No 0650074), and the Center for Smart Materials of The Hong Kong Polytechnic University.
文摘Lead-free piezoelectric ceramics 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 + xmol% Co3+ (BNBT-Co, x = 0-8) are prepared by the solid state reaction method. Effects of the amount of Co^3+ on the electrical properties and phase transition are studied. The results indicate that the addition of Co^3+ enhances the mechanical quality factor Q^3+ significantly, whereas the dissipation factor tanδ has a minimum value at x = 3.5. Meanwhile, addition of Co^3+ leads to small decreases of piezoelectric constant d33, and planar electromechanical coupling kp. The present 0.92(Bio.aNao.5) TiO3-0.08BaTiO3+3.5 moi% Co^3+ ceramics exhibit good performance with mechanical quality factor Qm = 910, piezoelectric constant d33 = 106pC/N, planar electromechanical coupling kp =10% and dissipation factor tanδ = 1.1% at 1 kHz. Saturated polarization hysteresis loops have been obtained for BNBT-Co ceramics. Two dielectric peaks at depolarization temperature Td and Tm appear in the curves of ε33^T vs temperature for the pure BNBT ceramics. However, the first dielectric peak Td disappears after the addition of Co^3+, which means that the transition from ferroelectric to antiferroelectric phase has been eliminated.
文摘The subband energy and lasing wavelength of compressively strained triangular Ino.53Ga0.47As/InAs quantum well are calculated and compared with the conventional rectangular ones with the same strain contents. The strain compensation using Al0.33In0.36Ga0.31As barrier is introduced. The results show that lasing wavelength can be extended dramatically to beyond 2.8μm by changing the energy band from the conventional rectangular shape to a triangular one, the realization of such a structure using molecular beam epitaxy technology is also discussed.
基金Supported by the Distinguished Youth Foundation of Hunan Province under Grant No 0333Y1008, the Science Foundation for Post doctorate of China under Grant No 2004035083, the Natural Science Foundation of Hunan Province under Grant No 063320034, and the Science Foundation of Central South University under Grant No 0601059.
文摘Based on the mechanism of injection, transport and recombination of the charge carriers, we develop a model to calculate the delay time of electroluminescence (EL) from bilayer organic light emitting diodes. The effect of injection, transport and recombination processes on the EL delay time is discussed, and the relationship between the internal interface barrier and the recombination time is revealed. "]~he results show that the EL delay time is dominated by the recombination process at lower applied voltage and by the transport process at higher applied voltage. When the internal interface barrier varies from 0.15 eV to 0.3 eV, the recombination delay time increases rapidly~ while the internal interface barrier exceeds about 0.3eV~ the dependence of the recombination delay time on applied voltage is almost undiversified, which may serve as a guideline for designing of a high-speed EL response device.
文摘Sr1-xLa2x/3Bi2Nb20O (0 ≤ x ≤0.2) ceramic samples are prepared by the solid-state reaction method. Their structure, dielectric and ferroelectric properties are investigated. The incorporation of La^3+ improves the den- sification and decreases the grain size of the ceramics without changing the crystal structure. The remanent polarization 2PT increases with increasing La content and reaches a maximum value of 22.8μC/cm^2 at x = 0.125, which is approximately 60% larger than that of pure SrBi2Nb2O9. The Curie temperature keeps almost unchanged at a value of about 440℃. The relationship between doping and the ferroeleetrie and dielectric properties are discussed.