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1.
A high sensitivity photovoltaic effect has been observed in a heterojunction composed of n-type wide bandgap oxide SrTiO 3-δ and p-type Si fabricated by laser molecular beam epitaxy.The responsivity of open-circuit photovoltage can reach 10 4 V/W without any amplification under zero bias for the wavelength range from visible to near infrared light in nW-μW order.We attribute the high performance of the photovoltage responsivity to the interfacial photoelectric effects in the SrTiO 3-δ /Si heterojunction.From the experimental results,some ideas can be generalized to improve photovoltaic efficiency and develop high sensitivity photodetectors with wide bandgap oxide materials and Si.  相似文献   

2.
We investigate the resistance and magnetoresistance (MR) of an entangled single-walled carbon nanotube (SWNT) network. The temperature dependence of conductance is fitted by formula G(T) = Go exp[-(To/T)^1/2] with To = 15.8 K at a wide temperature range from 4 K to 300K. The MR defined by [R(T, H) - R(T, 0)]/ R(T, 0) as a function of temperature and magnetic field perpendicular to the tube axis is negative at low temperatures. The MR amplitude increases as the temperature decreases at relative high temperature, but becomes decrease when temperature below 4 K. The results are explained in terms of the coherent hopping of carriers in the presence of a Coulomb gap at low temperature.  相似文献   

3.
We report the current-voltage (Ⅰ-Ⅴ) characteristics and electrical conductivity of individual template-synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires (190 ± 6 nm in diameter and δRT = 11.2 ± 2Ω^-1 cm^-1) over a wide temperature range from 300 to 10K. With lowering temperature, the Ⅰ - Ⅴ characteristics become nonlinear around 50K, and a clear Coulomb gap-like structure appears in the differential conductance (dI/dV) spectra. The temperature dependence of the resistance below 70 K follows In R α T^-1/2, which can be interpreted as Efros-Shklovskii hopping conduction in the presence of a Coulomb gap. In addition, the influences of measurement methods such as the applied bias voltage magnitude, the two-probe and four-probe techniques used in the resistance measurements are also reported and discussed.  相似文献   

4.
马争争  李建青  田召明  邱洋  袁松柳 《中国物理 B》2012,21(10):107503-107503
The 0.6(Bi1-xLax)FeO 3-0.4SrTiO 3(x = 0,0.1) multiferroic ceramics are prepared by a modified Pechini method to study the effect of substitution of SrTiO3 and La in BiFeO3.The X-ray diffraction patterns confirm the single phase characteristics of all the compositions each with a rhombohedral structure.The magnetic properties of the ceramics are significantly improved by a solid solution with SrTiO3 and substitution of La.The values of the dielectric constant ε r and loss tangent tan δ of all the samples decrease with increasing frequency and become constant at room temperature.The La-doped 0.6BiFeO3-0.4SrTiO3 ceramics exhibit improved dielectric and ferroelectric properties,with higher dielectric constant enhanced remnant polarization(Pr) and lower leakage current at room temperature.Compared with a anti-ferromagnetic BiFeO3 compound,the 0.6(Bi0.9La0.1)FeO3-0.4SrTiO3 sample shows the optimal ferromagnetism with remnant magnetization M r ~ 0.135 emμ/g and ferroelectricity with Pr ~ 5.94 μC/cm 2 at room temperature.  相似文献   

5.
We have fabricated colossal magnetoresistive (CMR) p-n unctions made of Te-doped LaMnO3 and Nb_dopoed SrTiO3 with laser molecular beam epitaxy.The I-V characteristics of the La 0.9Te0.1MnO3/SrNb 0.01Ti0.99O3p-n junctions as a function of applied magnetic field(0-5T) wrer experimentally studied in the temperature range 77-300K.The results indicate that the p-n junction exhibited the CMR behaviour.The magnetoresistance (MR) is positive at 220K and 300K,while it displays a negative MR at 77K.For a positive bias.the MR ratios (ΔR/R0,ΔR=RH-R0)are 7.5% at 0.1T and 18% at 5T for 300K,5%at 0.1T and 33%at 5T for 220K,for 300K,5.1%at 0.1T and 15%at 3T for 220K-19%at 0.1T and -72% at 5T for 77K,The CMR behaviour of the p-n junction is different from those of the LaMnO3 compound family.  相似文献   

6.
In this letter, we discuss the increase in the average cluster size by lowering the stagnation temperature of the methane (CH4) gas. The Coulomb explosion experiments are conducted to estimate the cluster size and the size distribution. The average CH4 cluster sizes Nay of 6 230 and 6 580 are acquired with the source conditions of 30 bars at 240 K and 60 bars at 296 K, respectively. Empirical estimation suggests a five-fold increase in the average size of the CH4 clusters at 240 K compared with that at room temperature under a backing pressure of 30 bars. A strong nonlinear Hagena parameter relation (Г^*∝ T0^-3.3) for the CH4 clusters is revealed. The results may be favorable for the production of large-sized clusters by using gases at low temperature and high back pressures.  相似文献   

7.
The microstructure,magnetic and transport properties of the heterogeneous system with a nominal composi-tion (1/m)Ag2O-La0.833K0.167MnO3 (1/m is molar ratio with m=32,16,8,4,and 2) have been studied.The x-ray diffraction patterns show that all the samples are two-phase composite and consist of a magnetic La0.833K0.167MnO3 (LKMO) perovskite phase and a nonmagnetic metal Ag phase.The room-temperature magnetoresistance (MR) effect is enhanced significantly due to the addition of Ag.For the m=4 sample,we obtain MR values up to 32% under a lower field of 0.5 T and 64% under a higher field of 5.5 T at the temperature of 300K,which are much larger than the corresponding MR values (10%and 35%) of the LKMO sample withoutAg.In the low-temperature range from 4.2K to 250K,the MR values of the Ag-added samples however decrease with the increasing Ag content in the samples.This effect is discussed qualitatively by using the relative contribution from the intrinsic MR effect and the extrinsic MR effect including the spin-polarized-tunnelling and spin-dependent scattering effects in different temperature regions.  相似文献   

8.
A manganite p-n heterojunction composed of Lao.67Sro.33MnO3 film and 0.05 wt% Nb-doped SrTiO3 substrate is fabricated. Rectifying behavior of the junction well described by the Shockley equation is observed, and the transport properties of the interface are experimentally studied. A satisfactorily logarithmic linear dependence of resistance on temperature is observed in a temperature range of 150 K-380 K, and the linear relation between bias and activation energies deduced from the R - lIT curves is observed. According to activation energy, the interfacial barrier of the heterojunction is obtained, which is 0.91 eV.  相似文献   

9.
This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature (T) dependence of electron spin relaxation times (T1) in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field (B) dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5.  相似文献   

10.
A Bi2Sr2Co2Oy/Si heterojunction is obtained by growing a layer of p-type oxygen-deficient Bi2Sr2Co2Oy film on a commercial n-type silicon wafer by pulsed laser deposition. Its rectifying and photovoltaic properties are studied in a wide temperature range from 20 K to 300 K. The transport mechanism under the forward bias can be attributed to a trap- filled space-charge-limited current conduction mechanism. Under the irradiation of a 532-nm continuous wave laser, a clear photovoltaic effect is observed and the magnitude ofphotovoltage increases as the temperature decreases, The results demonstrate the potential application of a Bi2SrzCo2Oy-based heterojunction in the photoelectronic devices.  相似文献   

11.
In the present work, a series of [Fe80Ni20–O/SiO2]n multilayer thin films is fabricated using a reactive magnetron sputtering equipment. The thickness of SiO2 interlayer is fixed at 3 nm, while the thickness values of Fe80Ni20–O magnetic films range from 10 nm to 30 nm. All films present obvious in-plane uniaxial magnetic anisotropy. With increasing the Fe80Ni20–O layer thickness, the saturation magnetization increases slightly and the coercivity becomes larger due to the enlarged grain size, which could weaken the soft magnetic property. The results of high frequency magnetic permeability characterization show that films with thin magnetic layer are more suitable for practical applications. When the thickness of Fe80Ni20–O layer is 10 nm, the multilayer film exhibits the most comprehensive high-frequency magnetic property with a real permeability of 300 in gigahertz range.  相似文献   

12.
The multilayer relaxation of the Rh(311) surface was investigated by means of LEED structure determination both for vertical and surface parallel (registry) relaxations. Excellent agreement between experimental and calculated spectra could be achieved mirrored by a minimum Pendry R-factor R = 0.174. The first three layer spacings are oscillatorily relaxed by Δd12/d0 = −14.5 ± 1.8%, Δd23/d0 = +4.9 ±2.0% and Δd34/d0 = −1.0 ±2.0%. There seems to be a coherent registry shift of the fir Δs = 0.03 ± 0.07 Å which, however, is within the error limits of the structure determination. Moreover, an energy dependent inner potential is detected. The results are discussed in comparison to equivalent surfaces of other materials as well as for the less open surfaces of rhodium.  相似文献   

13.
Effects of ZnO addition on electrical properties and low-temperature sintering of BiFeO3-modified Pb(Zr,Ti)O3–Pb(Fe2/3W1/3)O3–Pb(Mn1/3Nb2/3)O3 were investigated. The investigations revealed that the sintering temperature can be decreased to 950 °C, and the favorable properties were obtained with 0.10 wt% ZnO added ceramics. The electrical properties were as follows: d33 = 313 pC/N, Kp = 0.56, tan δ = 0.0053, εr = 1407 and Tc = 295 °C, which showed that this system was a promising material for the multilayer devices application.  相似文献   

14.
In this paper, a ZnS/Ag/MoO3 (ZAM) nano-multilayer structure is designed theoretically and optimum thicknesses of each layer are calculated. ZnS/Ag/MoO3 multilayer films with optimized thicknesses have also been fabricated on glass substrates by thermal evaporation method at room temperature. The structural, electrical and optical properties of ZnS/Ag/MoO3 multilayer are investigated with respect to the variation of annealing temperature. X-ray diffraction patterns show that increase in annealing temperature increases the crystallinity of the structures. High-quality multilayer films with the sheet resistance of 4.5 Ω/sq and the maximum optical transmittance of 85% at 100 °C annealing temperature are obtained. The allowed direct band gap for annealing at different temperatures is estimated to be in the range of 3.37–3.79 eV. The performance of the ZAM multilayer films are evaluated using a predefined figure of merit. These multilayer films can be used as transparent conductive electrodes in optoelectronic devices such as solar cells and organic light emitting diodes.  相似文献   

15.
用甘氨酸-硝酸盐(GNP)方法合成出La2/3(Ca0.65 Ba0 35)1/3MnO30.035/TiO2/xCuO纳米复合材料(x=0;0.23;0.25;0.27;0.30).通过X射线衍射、Raman光谱、扫描电子显微镜和磁电阻效应测试,对合成产物的结构及性能进行表征.结果表明,样品的对称性由立方向正交结构畸...  相似文献   

16.
In order to investigate of cobalt-doped interracial polyvinyl alcohol (PVA) layer and interface trap (Dit) effects, A1/p- Si Schottky barrier diodes (SBDs) are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance (Rs), and interfacial layer. Both the real and imaginary parts of dielectric constant (er and err) and electric modulus (Mr and Mrr), loss tangent (tan~), and AC electrical conductivity (aac) are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance (C) and conductance (G/w) values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si (MPS) type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance (CLF-CHF) method.  相似文献   

17.
徐明祥  焦正宽 《物理学报》1998,47(6):1006-1011
采用固态反应法制备了In替代的(La2/3Ca1/3)(Mn(3-2x)/3In2x/3)O3(x=0.00,0.10,0.15)体系.通过测量其零场和1.6T磁场下样品的电阻-温度关系以及一定温度下磁电阻率与磁场的关系.发现随In3+替代量的增加其磁电阻峰和电阻峰均向低温方向移动,同时巨磁电阻效应减弱,磁电阻峰也展宽.这是由于In3+替代量的变化,引起 关键词:  相似文献   

18.
In this study, the effects of doping by 3d (V, Mn, Fe, Ni) and 4f (Nd, Sm, Er) ions on dielectric and infrared properties of SrTiO3 (STO) single crystals are investigated. It is well known that doping of the SrTiO3 can change the dielectric properties of the STO from an insulator to an n-type semiconductor, and even to a metallic conductor. Dielectric and infrared (IR) properties of the undoped STO and doped STO single crystals are analyzed using dielectric spectroscopy (80 kHz-5 MHz), transmission (200 cm^-1-4000 cm^-1), and reflection spectroscopy (50 cm^-1-2000 cm^-1). It is found that doping by the 3d ions reduces the value of dielectric permittivity, but the trend of temperature dependence of the dielectric permittivity remains almost unchanged. On the other hand, dielectric spectroscopy measurements for samples doped by 4f ions show the anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition. There are two fractures of temperature dependences of inverse dielectric permittivity εr^-1 (T). Transmittance spectroscopy measurements show that there are differences in the shape of the spectrum in the mid-IR region between the undoped STO and the one doped by 4f ions. The differences in the reflectance spectrum between the STO:Nd and STO are analyzed in detail.  相似文献   

19.
何利民  冀钰  鲁毅  吴鸿业  张雪峰  赵建军 《物理学报》2014,63(14):147503-147503
通过传统固相反应法制备了钙钛矿锰氧化物(La1-xEux)4/3Sr5/3Mn2O7(x=0,0.15)多晶样品,并且对其磁性和电性进行了研究.磁性测量表明:随着温度的降低,样品经历了一个复杂的转变过程,在温度为T*时经历二维短程铁磁有序转变,在温度为TC时进入三维长程铁磁态.随着Eu的掺杂,T*和TC减小,并且样品(La0.85Eu0.15)4/3Sr5/3Mn2O7在低温区表现出自旋玻璃行为.电性质测量表明:在母体La4/3Sr5/3Mn2O7中La位掺杂Eu后电阻率明显变大,金属绝缘转变温度TMI降低,磁电阻峰值增大.这些影响归因于较小的Eu3+离子替代La3+离子导致平均离子半径减小,晶格发生畸变.此外,较小的Eu3+离子优先占据层间岩盐层的R-site,使La3+,Sr3+,Eu3+离子在(La0.85Eu0.15)4/3Sr5/3Mn2O7中的分布更加有序,所以x=0.15的样品的ρ-T曲线只有一个峰.  相似文献   

20.
The [(Pb0.90La0.10)Ti0.975O3/PbTiO3]n (PLT/PT)n (n = 1-6) multilayer thin films were deposited on the PbOx(1 0 0)/Pt/Ti/SiO2/Si substrates by RF magnetron sputtering method. The layer thickness of PbTiO3 in one periodicity kept unchanged, and the layer thickness of (Pb0.90La0.10)Ti0.975O3 is varied. The electrical properties of the (PLT/PT)n multilayer thin films were investigated as a function of the periodicity (n) and the orientation. The studied results show that the PbOx buffer layer results in the (PLT/PT)n films’ (1 0 0) orientation, and the (1 0 0)-oriented (PLT/PT)n multilayer thin films with n = 2 exhibit better pyroelectric properties and ferroelectric behavior than those of (PLT/PT)n films with other periodicities and orientations. The underlying physical mechanism for the enhanced electrical properties of (PLT/PT)n multilayer thin films was carefully discussed in terms of the periodicities and orientations.  相似文献   

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