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1.
In this study, we investigated the lattice structure, electrical resistivity, and optical conductivity of Nd0.5Sr0.5MnO3 thin films grown on SrTiO3 (001) and SrTiO3 (011) substrates. The thin film on SrTiO3 (001) experiences isotropic tensile strain and shows characteristics of the semiconducting ground state. On the other hand, the thin film on SrTiO3 (011) experiences anisotropic tensile strain, which means that one of the two in-plane lattice axes is fixed by the substrate lattice and the other axis is relaxed. The thin film shows the insulator–metal phase transition at 220 K and characteristics of the charge-ordered insulating ground state below 150 K. By comparing the single crystal data of the lattice along with the resistivity and optical conductivity, we suggest that the substrate strain affects the electronic structure as well as the carrier dynamics of the Nd0.5Sr0.5MnO3 thin films. We propose the possible ground states formed in the thin films.  相似文献   

2.
BiFeO3 (BFO) thin films with BaTiO3 (BTO) or SrTiO3 (STO) as buffer layer were epitaxially grown on SrRuO3-covered SrTiO3 substrates. X-ray diffraction measurements show that the BTO buffer causes tensile strain in the BFO films, whereas the STO buffer causes compressive strain. Different ferroelectric domain structures caused by these two strain statuses are revealed by piezoelectric force microscopy. Electrical and magnetical measurements show that the tensile-strained BFO/BTO samples have reduced leakage current and large ferroelectric polarization and magnetization, compared with compressively strained BFO/STO. These results demonstrate that the electrical and magnetical properties of BFO thin films can be artificially modified by using a buffer layer.  相似文献   

3.
KTa0.5Nb0.5O3 thin films were synthesized via a metal-organic solution. Characteristics were measured, such as X-ray diffraction pattern, surface morphology and roughness, and electric properties. The synthesized films have a (100) preferential growth orientation on Si (100) substrate. The homogeneous microstructure and smooth surface benefit to the good electric properties of the thin films. The current density-voltage characteristic shows an unexpected feature of the transition from linear to nonlinear, which can be explained by the space-charge-limited mode. Dielectric constant and loss of the thin films decrease with the increase of frequency. The decrease of dielectric loss is related to the decrease of net polarization in material. The decrease of dielectric constant can be explained by Debye formula. The phase transition temperature T c is about 102 °C for KTa0.5Nb0.5O3 materials.  相似文献   

4.
Ba0.5Sr0.5Ti0.99Co0.01O3 (BSTC) thin films have been fabricated with pulsed laser deposition on Nb-doped SrTiO3 (STN) substrate. In Pt/BSTC/STN capacitor, we systematically investigated the capacitance, leakage current and polarization versus bias voltage characteristics, and found that curves of capacitance versus voltage and leakage current versus voltage were not symmetric, and polarization hysteresis loop exhibited large relaxation of the remnant polarization at negatively poled state. A detailed analysis of capacitance data demonstrated a difference of the built-in voltage between top Pt/BSTC interface (Vb,t=2.5 V) and bottom BSTC/STN interface (Vb,b=1.1 V). Such different built-in voltages lead to the presence of an internal electric field, which results in asymmetric electric characteristics in Pt/BSTC/STN capacitor.  相似文献   

5.
Thickness‐dependent stress relaxation and its influence on the bandgap of BiFeO3 have been investigated. BiFeO3 films with 15 at% Bi excess allow the control of lattice mismatch‐induced biaxial stress up to 10.8 GPa on SrTiO3(001) substrates. Heteroepitaxy of such films follows the Stranski–Krastanov growth mode, as suggested by island formation on the wetting layer accompanied with stress relaxation. The bandgap is linearly decreased with the in‐plane compressive stress, and a large stress coefficient of 67 meV/GPa was extracted. A 0.7 eV red‐shift of the bandgap was observed in the fully epitaxially strained film. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

6.
Mn-doped (Bi0.5Na0.5)TiO3-BaTiO3 (BNBMT) thin film with the composition near the morphotropic phase boundary was grown on (La0.6Sr0.4)CoO3-electroded SrTiO3 single-crystal substrate by using pulsed laser deposition method. Ascribed to the crystal structure and lattice similarity, (100)-oriented BNBMT film with pure single-phase perovskite structure was obtained through carefully controlling the growth conditions. Enhanced ferroelectric and dielectric properties were obtained with large remanent polarization P r of ~21 μC/cm2, coercive field E c of ~7.4 kV/mm and dielectric constant $\varepsilon_{33}^{T}/\varepsilon_{0}$ of ~750 at 1 kHz. The excellent global electrical properties of the BNBMT film are promising for environmentally friendly ferroelectric devices.  相似文献   

7.
Time‐resolved two color pump‐probe polarization spectroscopy was performed at room temperature on SrTiO3 films grown directly on Si with film thickness varying from 2 nm to 7.8 nm. An E‐symmetry mode with a characteristic frequency of 0.2 THz is impulsively generated and measured in these coherently strained tetragonal phase SrTiO3 thin films. A superimposed exponentially decaying signal observed indicates the possible relaxational hopping of Ti ion between double potential wells. The dependence of the coherent phonon signal on pump and probe laser polarization helps to identify the symmetry of the phonon modes.  相似文献   

8.
A highly sophisticated pulsed laser deposition (PLD) chamber has recently been installed at the NANO beamline at the synchrotron facility ANKA (Karlsruhe, Germany), which allows for comprehensive studies on the PLD growth process of dielectric, ferroelectric and ferromagnetic thin films in epitaxial oxide heterostructures or even multilayer systems by combining in situ reflective high‐energy diffraction with the in situ synchrotron high‐resolution X‐ray diffraction and surface diffraction methods. The modularity of the in situ PLD chamber offers the opportunity to explore the microstructure of the grown thin films as a function of the substrate temperature, gas pressure, laser fluence and target–substrate separation distance. Ba0.5Sr0.5TiO3 grown on MgO represents the first system that is grown in this in situ PLD chamber and studied by in situ X‐ray reflectivity, in situ two‐dimensional reciprocal space mapping of symmetric X‐ray diffraction and acquisition of time‐resolved diffraction profiles during the ablation process. In situ PLD synchrotron investigation has revealed the occurrence of structural distortion as well as domain formation and misfit dislocation which all depend strongly on the film thickness. The microstructure transformation has been accurately detected with a time resolution of 1 s. The acquisition of two‐dimensional reciprocal space maps during the PLD growth has the advantage of simultaneously monitoring the changes of the crystalline structure as well as the formation of defects. The stability of the morphology during the PLD growth is demonstrated to be remarkably affected by the film thickness. A critical thickness for the domain formation in Ba0.5Sr0.5TiO3 grown on MgO could be determined from the acquisition of time‐resolved diffraction profiles during the PLD growth. A splitting of the diffraction peak into two distinguishable peaks has revealed a morphology change due to modification of the internal strain during growth.  相似文献   

9.
A strain gradient induced by mechanical bending on a SrTiO3 substrate is demonstrated, and has a pronounced influence on the carrier density and mobility of the interfacial 2D electron gas at the LaAlO3/SrTiO3 heterointerface. Tensile and compressive strain gradients represent two states of upward and downward bending. Under the tensile strain gradient, the carrier density decreases and the mobility has about 200% increase. Conversely, under the compressive strain gradient, the mobility decreases and the carrier density increases by up to 107%. These results demonstrate a range of opportunities to modulate the carrier density and mobility at oxide heterointerface and open up a promising way for further research on application of oxide devices.  相似文献   

10.
M. Zhang  X. L. Ma  D. X. Li 《哲学杂志》2013,93(15):1625-1636
The microstructures present in a thin film of La0.7Sr0.3MnO3, grown by computer-controlled laser molecular beam epitaxy on a SrTiO3 (001) substrate, were characterized by means of cross-section and plan-view transmission electron microscopy. Four kinds of rhombohedral-oriented domains and two types of domain boundaries were identified in the film. The crystallographic relationships between each domain and the substrate were established on the basis of a hexagonal unit cell using Miller–Bravais indices. A mechanism for the formation of the oriented domains is proposed from the viewpoint of the evolution of strain relaxation during film preparation.  相似文献   

11.
Strained epitaxial La0.5Sr0.5CoO3 films are grown on LaAlO3 substrate. Structural, electrical, and magnetic measurements were carried out. Out of plane lattice parameter of the film undergoes compressive strain and the coercivity is enhanced. The zero field cooled (ZFC) magnetization curve for a field applied parallel to the film plane shows a jump, which suggests a spin reorientation transition (SRT), while ZFC magnetization for a field applied perpendicular to the film plane is featureless. This jump in magnetization is shifted to higher temperatures when the magnetic field is reduced. The SRT is attributed to the strain in the film.  相似文献   

12.
采用脉冲激光沉积法分别在(100)LaAlO3和(100)SrTiO3基片上生长了La0.33Pr0.34Ca0.33MnO3薄膜,并通过磁测量和电输运测量对生长在不同基片上的La0.33Pr0.34Ca0.33MnO3薄膜的物性进行了研究.结果表明,基片和薄膜之间的压应力导致La关键词: 钙钛矿锰氧化物 相分离 电荷有序  相似文献   

13.
利用脉冲激光沉积技术在掺Nb的SrTiO3衬底上制备了氧非正分La0.9Ba0.1MnO3-δ/SrTiO3:Nb p-n异质结.在20—300K这一较宽的温度范围内获得了光滑的整流曲线.整流实验表明:该p-n异质结的正向扩散电压VD随着温度升高在薄膜金属—绝缘转变温度附近出现极大值,表现出与氧正分La0.9Ba0. 关键词: 0.9Ba0.1MnO3-δ薄膜')" href="#">La0.9Ba0.1MnO3-δ薄膜 锰氧化物p-n结 整流性质  相似文献   

14.
The local structure around In atoms in an m‐plane In0.06Ga0.94N film coherently grown on a freestanding m‐plane GaN substrate was investigated by polarization‐dependent X‐ray absorption fine‐structure. A step‐by‐step fitting procedure was proposed for the m‐plane wurtzite structure. The interatomic distance for the first nearest neighbour In—N atomic pairs was almost isotropic. For the second nearest In—Ga pairs, the interatomic distances along the m‐ and a‐axes were longer and shorter, respectively, than that in strain‐free virtual crystals as expected for the m‐plane compressive strain. In contrast, the In—Ga interatomic distance in the c‐direction was elongated in spite of the compressive strain, which was explained in terms of the anisotropic atomic structure on the m‐plane. The local strain in the m‐plane film was more relaxed than that in coherently grown c‐plane single quantum wells. A few In atoms were atomically localized in all directions, and thus localized excitonic emission is expected as in the case of c‐plane InGaN.  相似文献   

15.
Current–voltage (JV) characteristics of epitaxial hetero-junctions composed of Pr0.7Ca0.3MnO3 and Nb:SrTiO3 were studied under forward and reversed bias conditions. Detailed analysis showed that the JV characteristics of these heterojunctions can be well-fitted by the thermally-assisted tunnelling model. While the dielectric constant of Nb:SrTiO3 extracted under the forward bias was about one order of magnitude smaller than that of bulk SrTiO3, the value obtained under reverse bias was very close to that of the bulk SrTiO3. The result can be explained by the existence of an interface layer on the Nb:SrTiO3 substrate with a smaller effective dielectric constant. The current finding suggested that the properties of interface layer should be taken into account in order to accurately simulate the JV characteristics of such heterojunctions.  相似文献   

16.
Low‐temperature Raman study of (001)‐oriented PrFeO3 thin film of around 200 nm thickness deposited on a LaAlO3 (001) substrate by using the pulsed‐laser deposition technique is presented. X‐ray diffraction analysis of this film shows an orthorhombic structure with Pbnm space group. The observed substrate‐induced strain is found to be small. In the room temperature Raman spectra, different Raman modes were observed that were classified according to the orthorhombic structure. All the observed modes show a decrease in wavenumber with rise in temperature, except the B1g mode (624 cm−1) which shows some anomalous behavior. We tried to correlate the variations in linewidth and position with temperature for the observed modes with the octahedral disorder of FeO6. Many possibilities are presented to explain the observed results. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

17.
The complete (001)-oriented thin films of La0.5Sr0.5CoO3-x (LSCO) are deposited on (001) SrTiO3 substrates by pulsed laser deposition under reduced oxygen pressure. It is revealed that the c axis of the film stretches with depleting oxygen. The magnetic, electrical, and magnetoresistive properties of the films are characterized by means of various techniques. Significant dependence of these properties on oxygen deficiency in the films is demonstrated, with enhanced magnetoresistance recorded for the samples deposited over a wide range of reduced oxygen pressure. Received: 9 July 1998 / Accepted: 15 January 1999 / Published online: 31 March 1999  相似文献   

18.
《Current Applied Physics》2015,15(5):584-587
We investigated ferroelectric characteristics of BiFeO3 (BFO) thin films on SrRuO3 (SRO)/yttria-stabilized zirconia (YSZ)/glass substrates grown by pulsed laser deposition. YSZ buffer layers were employed to grow highly crystallized BFO thin films as well as SRO bottom electrodes on glass substrates. The BFO thin films exhibited good ferroelectric properties with a remanent polarization of 2Pr = 59.6 μC/cm2 and fast switching behavior within about 125 ns. Piezoelectric force microscopy (PFM) study revealed that the BFO thin films have much smaller mosaic ferroelectric domain patterns than epitaxial BFO thin films on Nb:SrTiO3 substrates. Presumably these small domain widths which originated from smaller domain energy give rise to the faster electrical switching behavior in comparison with the epitaxial BFO thin films on Nb:SrTiO3 substrates.  相似文献   

19.
采用多种X射线衍射技术和磁电阻测量技术研究了不同厚度的La0.8Ca0.2MnO3/SrTiO3 (LCMO/STO)薄膜的应变状态及其对磁电阻性能的影响.结果表明,在STO(001)单晶衬底上生长的LCMO薄膜沿[00l]取向生长.LCMO薄膜具有伪立方钙钛矿结构,随着薄膜厚度的增加,面内晶格参数增加,垂直于面内的晶格参数减小,晶格参数ab相近,略小于c.LC 关键词: X射线衍射 微结构 应变 物理性能  相似文献   

20.
New ferroelectric Pb(Zr,Ti)O3-Pb(Mn,W,Sb,Nb)O3 (PZT-PMWSN) thin film has been deposited on a Pt/Ti/SiO2/Si substrate by pulsed laser deposition. Buffer layer was adopted between film and substrate to improve the ferroelectric properties of PZT-PMWSN films. Effect of a Pb(Zr0.52Ti0.48)O3 (PZT) and (Pb0.72La0.28)Ti0.93O3 (PLT) buffer layers on the stabilization of perovskite phase and the suppression of pyrochlore phase has been examined. Role of buffer layers was investigated depending on different types of buffer layer and thickness. The PZT-PMWSN thin films with buffer layer have higher remnant polarization and switching polarization values by suppressing pyrochlore phase formation. The remnant polarization, saturation polarization, coercive field and relative dielectric constant of 10-nm-thick PLT buffered PZT-PMWSN thin film with no pyrochlore phase were observed to be about 18.523 μC/cm2, 47.538 μC/cm2, 63.901 kV/cm and 854, respectively.  相似文献   

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