共查询到20条相似文献,搜索用时 31 毫秒
1.
L. Despont C. Lichtensteiger F. Clerc M. G. Garnier F.J. Garcia de Abajo M. A. Van Hove J.-M. Triscone P. Aebi 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(2):141-146
Full hemispherical X-ray photoelectron diffraction (XPD) experiments have been performed to investigate at the atomic level
ultrathin epitaxial c-axis oriented PbTiO3 (PTO) films grown on Nb-doped SrTiO3 substrates. Comparison between experiment and theory allows us to identify a preferential ferroelectric polarization state
in a 60 ? -thick PTO film. Multiple scattering theory based on a cluster-model [ Phys. Rev. B
, 075404 (2001)] is used to simulate the experiments. 相似文献
2.
Meng He 《Applied Surface Science》2007,253(14):6080-6084
La0.9Sr0.1MnO3 (LSMO) ultrathin films with various thickness (in the range of 5-50 unit cells) are grown on (0 0 1) substrates of the single-crystal SrTi0.99Nb0.01O3 by laser molecular-beam epitaxy (laser-MBE), and the surface morphology of these films were measured by scanning tunneling microscopy (STM). STM images of LSMO ultrathin film surface reveal that surface morphology becomes more flat with increasing film thickness. This study highlights the important effect of strain caused by the lattice mismatch between substrates and ultrathin films. And the results should be useful to the investigations on growing manganite perovskite materials. 相似文献
3.
Ab initio total energy Hartree-Fock calculations of ultrathin films of α-Al2O3 on (0 0 0 1) α-Cr2O3 templates are presented. The surface relaxation, the in-plane reconstruction and the surface and strain energies of the slabs are studied as a function of alumina film thickness. The surface Al layer is found to relax inwards considerably, with the magnitude of the inwards relaxation depending on the thickness of the ultrathin alumina film in a non-linear manner. The calculations also reveal that ultrathin films of alumina lower the surface energy of (0 0 0 1) α-chromia substrates. This indicates that the (0 0 0 1) α-chromia surface provides favourable conditions for the templated growth of α-alumina. However, increasing the alumina film thickness is found to give rise to a significant increase in strain energy. Finally, the electronic properties at the surface of the (0 0 0 1) α-Al2O3/α-Cr2O3 slabs are investigated. Here it is found that the alumina coating gives rise to an increase in the covalency of the bonds at the surface of the slabs. In contrast, the influence of an alumina layer on the electrostatic potential at the surface of the chromia slab is relatively minor, which should also be beneficial for the templated growth of α-alumina on (0 0 0 1) α-chromia substrates. 相似文献
4.
Tao Hu Hao Fu Zan Zheng Ning Ma Piyi Du 《Applied Physics A: Materials Science & Processing》2014,117(3):1171-1177
(100) Oriented Pb x Sr1?x TiO3 (PSTO) thin films are prepared on indium tin oxide (ITO)/glass substrates by sol–gel technique while inserting doped PbTiO3 (PTO)-inducing layer in between. The effect of tensile stress in PSTO on tunability and (100) orientation of the thin films was investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscope, and atomic force microscope, respectively. Results show that PSTO thin film deposited on doped PTO has (100) oriented structure while it is randomly oriented when deposited directly on the ITO/glass substrate. Lattice mismatch between PSTO and PTO appears, in which the in-plane lattice constant c is 0.3922–0.3924 nm in the former and 4.02–4.07 nm in the latter, respectively, contributing tensile stress in the PSTO due to different lattice constants between them. The stress in the PSTO thin film is 3.04, 3.15, 3.59 and 4.47 GPa when the doped PTOs are Fe–PTO, Tb–PTO, Co–PTO and Zn–PTO, respectively. The orientation degrees of PSTO thin films are from 89.63, 90.31, 91.92 to 93.29 % with increasing stress of PSTO on Fe–PTO, Tb–PTO, Co–PTO and Zn–PTO, respectively. Tunabilities of the well-oriented PSTO thin films increase in ascending order of 63 < 65 < 69 < 73 % when induced by oriented PTO layers of Fe–PTO, Tb–PTO, Co–PTO and Zn–PTO, respectively, which is in accordance with the degree of (100) orientation appearing in the thin films. The high tunability appears in the PSTO thin film while high (100) orientation is derived from the tensile stress. It is much higher than that of randomly oriented PSTO thin film. 相似文献
5.
《Physica C: Superconductivity and its Applications》1999,311(1-2):42-48
Atomic-layer-controlled molecular beam epitaxy (ALC-MBE) technique is applied for preparing Bi2Sr2CaCu2Ox ultrathin films. Precise control of the composition by ALC-MBE enables successful growth of particle-free ultrathin films. Superconducting zero-resistance transitions are observed for the films more than 3.0 nm in thickness. It is also shown that growth of a Bi2Sr2CuOy buffer layer between the film and SrTiO3(100) substrate contributes to preparing such particle-free ultrathin films with good superconducting properties. 相似文献
6.
We investigated the optical response of La0.67Sr0.33MnO3 (LSMO) films which show the metal-insulator transition (MIT) with the film thickness dependence. By using spectroscopic ellipsometric technique we found that the optical spectra below the charge transfer gap exhibited the coherent-incoherent crossover behavior through MIT. The formation of the incoherent mode near 1.5 eV was reminiscent of the polaron absorption which had been widely observed in various manganites. We suggest that the electron-phonon coupling could be enhanced due to low dimensionality in the ultrathin LSMO film in consideration of orbital polarization. 相似文献
7.
J. P. B. Silva K. C. Sekhar A. Almeida J. Agostinho Moreira M. Pereira M. J. M. Gomes 《Applied Physics A: Materials Science & Processing》2013,113(3):817-824
The Ba0.8Sr0.2TiO3 thin films were grown on the Pt–Si substrate at 700 °C by using a pulsed laser deposition technique at different oxygen partial pressure (PO2) in the range of 1–20 Pa and their properties were investigated. It is observed that the PO2 during the deposition plays an important role on the tetragonal distortion ratio, surface morphology, dielectric permittivity, ferroelectric polarization, switching response, and leakage currents of the films. With an increase in PO2, the in-plane strain for the BST films changes from tensile to compressive. The films grown at 7.5 Pa show the optimum dielectric and ferroelectric properties and also exhibit the good polarization stability. It is assumed that a reasonable compressive strain, increasing the ionic displacement, and thus promotes the in-plane polarization in the field direction, could improve the dielectric permittivity. The butterfly features of the capacitance–voltage (C–V) characteristics and the bell shape curve in polarization current were attributed to the domain reversal process. The effect of pulse amplitude on the polarization reversal behavior of the BST films grown at PO2 of 7.5 Pa was studied. The peak value of the polarization current shows exponential dependence on the electric field. 相似文献
8.
K.-I. Akabori K. Tanaka A. Takahara T. Kajiyama T. Nagamura 《The European physical journal. Special topics》2007,141(1):173-180
Mechanical relaxation behavior in ultrathin polystyrene
(PS) films supported on silicon oxide (SiOx) and gold (Au) substrates
has been studied by dynamic viscoelastic measurement. Based on the method,
effects of free surface and substrate interface on the segmental dynamics
were discussed. In the case of thin PS films with a thickness of
approximately 200 nm, αa-relaxation process corresponding to
the segmental motion did not show any deviation from the bulk behavior. In
contrast, for the films thinner than about 50 nm, the relaxation time
distribution for the αa-process became broader, probably due to
a mobility gradient in the surface and interfacial regions. When we
sandwiched an ultrathin PS film between SiOx layers, another relaxation
process, in addition to the original αa-process, appeared at a
higher temperature side that we assigned to the interfacial αa-relaxation
process. However, this was never seen for an ultrathin PS
film between Au layers, implying that restriction from the substrate
interface might be weak in this case. 相似文献
9.
We determine the effects of film thickness, epitaxial strain and the nature of electrodes on ferroelectric phase transitions
in ultrathin films of BaTiO3 using a first-principles effective Hamiltonian in classical molecular dynamics simulations. We present results for polarization
and dielectric properties as a function of temperature and epitaxial strain, leading to size-dependent temperature-strain
phase diagram for the films sandwiched between ‘perfect’ electrodes. In the presence of non-vanishing depolarization fields
when non-ideal electrodes are used, we show that a stable stripe-domain phase is obtained at low temperatures. The electrostatic
images in the presence of electrodes and their interaction with local dipoles in the film explain these observed phenomena.
相似文献
10.
We have carried out a detailed investigation on the size effect on SrRuO3/BaTiO3/SrRuO3 ferroelectric ultrathin film capacitors with film thickness fully strained with a SrTiO3 substrate. We employ the transverse field Ising model, taking into account the incomplete charge compensation of the realistic SrRuO3 electrode and the misfit strain imposed by the SrTiO3 substrate in the Hamiltonian, to quantitatively explain the experimental observation in the literature. It is found that BaTiO3 ultrathin films between two metallic electrodes lose their ferroelectric properties below a critical thickness of about 4.17 nm due to the enhancement of the quantum effect under the influence of the incomplete charge compensation of the electrode. 相似文献
11.
Ellison CJ Kim SD Hall DB Torkelson JM 《The European physical journal. E, Soft matter》2002,8(2):155-166
Fluorescence intensity measurements of chromophore-doped or -labeled polymers have been used for the first time to determine
the effects of decreasing film thickness on glass transition temperature, T
g, the relative strength of the glass transition, and the relative rate of physical aging below T
g in supported, ultrathin polymer films. The temperature dependence of fluorescence intensity measured in the glassy state
of thin and ultrathin films of pyrene-doped polystyrene (PS), poly(isobutyl methacrylate) (PiBMA), and poly(2-vinylpyridine)
(P2VP) differs from that in the rubbery state with a transition at T
g. Positive deviations from bulk T
g are observed in ultrathin PiBMA and P2VP films on silica substrates while substantial negative deviations from bulk T
g are observed in ultrathin PS films on silica substrates. The relative difference in the temperature dependences of fluorescence
intensity in the rubbery and glassy states is usually reduced with decreasing film thickness, indicating that the strength
of the glass transition is reduced in thinner films. The temperature dependence of fluorescence intensity also provides useful
information on effects of processing history as well as on the degree of polymer-substrate interaction. In addition, when
used as a polymer label, a mobility-sensitive rotor chromophore is demonstrated to be useful in measuring relative rates of
physical aging in films as thin as 10 nm.
Received 21 August 2001 相似文献
12.
Dong-Xu Zhang Yu-Xiang Zheng Qing-Yuan Cai Wei Lin Kang-Ning Wu Peng-Hui Mao Rong-Jun Zhang Hai-bin Zhao Liang-Yao Chen 《Applied Physics A: Materials Science & Processing》2012,108(4):975-979
An effective method for determining the optical constants of Ta2O5 thin films deposited on crystal silicon (c-Si) using spectroscopic ellipsometry (SE) measurement with a two-film model (ambient–oxide–interlayer–substrate) was presented. Ta2O5 thin films with thickness range of 1–400 nm have been prepared by the electron beam evaporation (EBE) method. We find that the refractive indices of Ta2O5 ultrathin films less than 40 nm drop with the decreasing thickness, while the other ones are close to those of bulk Ta2O5. This phenomenon was due to the existence of an interfacial oxide region and the surface roughness of the film, which was confirmed by the measurement of atomic force microscopy (AFM). Optical properties of ultrathin film varying with the thickness are useful for the design and manufacture of nano-scaled thin-film devices. 相似文献
13.
Y.S. Dedkov M. Fonin U. Rüdiger G. Güntherodt 《Applied Physics A: Materials Science & Processing》2006,82(3):489-493
The surface structure and electronic properties of ultrathin MgO layers grown on epitaxial Fe(110) films were investigated
at room temperature by means of electron diffraction, Auger electron spectroscopy, scanning tunneling microscopy, and spin-resolved
photoelectron spectroscopy. The spin polarization at the Fermi level (EF) of the Fe(110) film decreases sharply with increasing thickness of the MgO layer. This behavior arises from the formation
of a thin FeO layer at the MgO(111)/Fe(110) interface, as revealed by structural and spectroscopic investigations. The strong
attenuation of the intrinsic spin polarization is qualitatively attributed to the scattering of spin-polarized electrons at
the unoccupied d-orbitals of Fe2+.
PACS 68.35.-p; 68.55.-a; 73.20.r; 75.70.Cn; 79.60.-I 相似文献
14.
《Solid State Communications》1986,60(5):449-452
The spin-wave excitations of ultrathin iron films (1 to 5 nm) on sapphire substrates have been studied by inelastic light scattering using Brillouin spectroscopy. The room temperature magnetization J, magnetic anisotropy field Ban, and the g-factor have been determined by fitting the measured ω-B results for surface spin waves to the related Damon-Eshbach theory. For thicknesses below 4 nm the film magnetization Jf decreases linearly with film thickness and is found substantially smaller than Jf values determined by static magnetization measurements. Equivalent reductions in Jf, however, were also obtained in light scattering studies of ultrathin Fe films on GaAs substrates reported previously in the literature [2]. 相似文献
15.
从Landau-Devonshire唯象理论出发,考虑到晶格失配导致的NFDA3位错应力场与极化场的耦合,研究了在SrTiO3衬底上外延生长的PbZr0.4Ti0.6O3薄膜厚度对其自发极化强度、电滞回线的影响. 结果表明,产生刃位错的PbZr0.4Ti0.6O3薄膜临界厚度为~1.27nm,当薄膜厚度大于临界厚度时,在所形成的位错附近,极化强度出现急剧变化,形成自发极化强度明显减弱的“死层”;随着薄膜厚度的减小,位错间距增大,“死层”厚度与薄膜总厚度之比增加. 由薄膜电滞回线的变化情况可知,其剩余极化强度随着薄膜厚度的减小而逐渐减小.
关键词:
铁电薄膜
自发极化强度
电滞回线
位错 相似文献
16.
A. S. Komolov S. A. Komolov E. F. Lazneva A. A. Gavrikov P. S. Repin 《Technical Physics》2012,57(2):256-261
The modification of the electronic structure during adsorption of ultrathin copper phthalocyanine (CuPc) and 3, 4, 9, 10 perylene-tetracarboxylic-dianhydride
(PTCDA) coatings on the surface of polycrystalline tin dioxide is traced. Auger electron spectroscopy is employed to find
changes in the atomic composition of the surface. It is found with the help of low-energy electron total current spectroscopy
using a testing beam of electrons with energies up to 30 eV that the total current spectra typical of organic films are formed
when the thickness of the coating being deposited is 2–7 nm. The formation of an interface layer 1.5–2.0 nm in thickness is
detected, in which the intensity of the structure of the total current spectra decreases and the effect of interaction of
PTCDA molecules with the SnO2 surface is manifested. 相似文献
17.
G. Ruano J.C. Moreno-López M.C.G. Passeggi R.A. Vidal J. Ferrón M.Á. Niño R. Miranda J.J. de Miguel 《Surface science》2012,606(5-6):573-579
The growth of ultrathin epitaxial layers of aluminum fluoride on Cu(100) has been studied by a combination of surface science techniques. Deposition at room temperature results in step decoration followed by the formation of dendritic two-dimensional islands that coalesce to form porous films. Ultrathin layers (up to 2 monolayers in thickness) are morphologically unstable upon annealing; de-wetting takes place around 430 K with the formation of three-dimensional islands and leaving a large fraction of the Cu surface uncovered. Films several nanometers thick, on the contrary, are stable up to ca. 730 K where desorption in molecular form sets on. The effect of electron irradiation on the AlF3 has also been characterized by different spectroscopic techniques; we find that even small quantities of stray electrons from rear electron beam heating can provoke significant decomposition of the aluminum fluoride, resulting in the release of molecular fluorine and the formation of deposits of metallic aluminum. These features make AlF3 an interesting material for spintronic applications. 相似文献
18.
L. Dolgov V. Kiisk R. Matt S. Pikker I. Sildos 《Applied physics. B, Lasers and optics》2012,107(3):749-753
It is demonstrated that the spectrum, direction and polarization of rare-earth fluorescence can be tailored by embedding the impurity ions into a planar metal–dielectric structure (MDS). The latter was designed by spin coating a rare-earth-doped oxide film (TiO2:Sm3+) onto a gold-covered glass substrate. For spectral–directional investigations of Sm3+ fluorescence, the MDS was attached to a semi-cylindrical prism and excited by UV light from the flat side. An angular scan revealed a strongly polarized and directional emission of Sm3+ from the convex side of the prism. The tuning of TiO2 film thickness in the MDS allows a control of the polarization and direction of the emission bands. A theoretical modeling of the reflectivity of the MDS suggests that the observed angular resonances in the fluorescence emission are caused by its effective coupling with surface plasmons on the gold–dielectric interface or coupling with leaky modes in sufficiently thick dielectric films working as a waveguides. 相似文献
19.
The growth of epitaxial ultrathin BaTiO3 films upon rf magnetron sputter deposition on a Pt(111) substrate has been studied by scanning tunnelling microscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy. The BaTiO3 films have been characterized from the initial stages of growth up to a film thickness of 4 unit cells. The deposited films develop a long-range order upon annealing at 1050 K in UHV. In the submonolayer regime a wetting layer is formed on Pt(111). Thicker films reveal a Stranski–Krastanov-like structure as observed with STM. By XPS a good agreement of the thin film stoichiometry with BaTiO3 single crystal data is determined. Due to annealing at 1150 K BaTiO3 forms large two-dimensional islands on the Pt(111) substrate. Different surface structures develop on the islands depending on the O2 partial pressure during annealing. 相似文献
20.
A. N. Chakravarti K. P. Ghatak K. K. Ghosh S. Ghosh A. Dhar 《Zeitschrift für Physik B Condensed Matter》1982,47(2):149-153
An attempt is made to investigate the effects of size quantization on the effective mass in ultrathin films ofn-Cd3As2. It is found that the effective mass at the Fermi level depends on the size quantum number due to the effect of crystal-field splitting, resulting in different effective masses at the Fermi level corresponding to different electric subbands. It is also observed that the different effective masses closely approach each other, for a given film thickness, with increasing electron concentration and, for a given electron concentration, with increasing film thickness. 相似文献