共查询到20条相似文献,搜索用时 15 毫秒
1.
V. Iannotti G. Ausanio C. Campana F. D’Orazio C. Hison F. Lucari L. Lanotte 《Journal of magnetism and magnetic materials》2008
Pulsed laser deposition (uPLD) in vacuum by means of subpicosecond laser pulses is a powerful, versatile technique for the production of films constituted by nanoparticles. On impact with the deposition substrate, the nanodrops ejected from the target assume an oblate ellipsoidal shape, solidifying with the major cross-section parallel to the substrate plane. These features and the difficult coalescence among the deposited nanoparticles are peculiar characteristics specific to the films obtained by uPLD. In the case of magnetic nanoparticle films obtained by means of this technique, a magnetization isotropy in the film plane and a hard magnetization axis orthogonal to the film plane are expected. This simple assumption, generated by the specific shape and orientation of the deposited nanoparticles, was not experimentally verified up to now. The present investigation represents the first experimental validation of magnetic anisotropy, determined by the peculiar morphology and topology of the constituent particles, in the uPLD NixSi100−x nanoparticle films. The in-plane isotropic magnetization behaviour, as well as the presence of a hard magnetization axis perpendicular to the sample surface were demonstrated for all investigated films. The difficult coalescence among the magnetic nanoparticles, even at high Ni volume fractions, is confirmed by the behaviour of the initial magnetization curve, typical for single-domain nanoparticles systems. 相似文献
2.
Sachi Morinaga Takashi Nishiyama Takashi Kajiwara Kunihito Nagayama 《Applied Physics A: Materials Science & Processing》2010,101(4):743-746
A compositionally graded thin film of FeSi2 was fabricated by a gravity-assisted pulsed laser ablation (GAPLA) system. By this method, a compositionally graded structure
was successfully produced under a gravity field of 5400 G. We demonstrate that the atomic fraction of Fe, the heavier component
of the thin film measured by scanning electron microscope/energy dispersive X-ray (SEM-EDX), showed increasing spatial distribution
with the direction of gravity. We found that optimal laser fluence exists to give a thin film having the largest possible
spatial compositional gradient. We found that surface energy density on the substrate surface is the key parameter to control
the composition distribution. Furthermore, the ratio of Fe/Si of the film did not match that of the target. This result shows
that the Si component is selectively etched during the film-forming process. Relatively high laser fluence as well as a very
narrow space between the target and the substrate are essential to etch the film once it is deposited, in order to re-ionize
and etch Si selectively while gravity accelerates both Fe and Si particles to the direction of gravity. We hypothesize that
this process accounts for both the change in the stoichiometry and the formation of composition distribution. 相似文献
3.
4.
P. Thakur J. C. Cezar N. B. Brookes R. J. Choudhary D. M. Phase K. H. Chae Ravi Kumar 《Hyperfine Interactions》2010,197(1-3):95-100
The electronic and magnetic properties of well characterized Mo1???xFexO2 (x = 0–0.5) thin films that show ferromagnetism at room temperature (RT) have been investigated by the means of near edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) experiments at the O K-, Fe L-, and Mo M-edges. The NEXAFS spectra at O K- and Mo M3,2 -edges show a strong hybridization of O 2p-4d Mo orbitals, and Mo ions change their symmetry with the substitution of Fe ions into MoO2 matrix. The Fe 2p NEXAFS/XMCD spectra exhibit multiple absorption peaks and an appreciable XMCD signal that persists even at RT. These results demonstrate that Fe is in a mixed valence state of Fe2?+?–Fe3?+?, substituting at the Mo site and that the Fe2?+?/3?+? ions are ferromagnetically polarized. 相似文献
5.
6.
Song Zhang Wenzhong Lu Chuanbin Wang Qiang Shen Lianmeng Zhang 《Physica B: Condensed Matter》2012,407(13):2382-2384
The stoichiometry of B–C thin films was controlled via pulsed laser deposition using a series of ceramic B–C targets (B/C ratio was 3.04–5.92). The effects of B/C ratio in target, laser power and substrate-to-target distance on deposition rate, microstructure, stoichiometry and chemical structure were investigated. The maximum deposition rate was obtained at laser power of 90 mJ and substrate-to-target distance of 50 mm. Boron rich B–C films were obtained and the stoichiometry in B–C thin films was controlled in the range 2.9–4.6. Carbon atoms were bonded with only sp3 hybridization when boron was rich,but with sp2 and sp3 hybridizations when carbon was rich. 相似文献
7.
M.J.M. Pires M.S. Araújo Filho J.C.G. Tedesco J.D. Ardisson W.A.A. Macedo 《Journal of Physics and Chemistry of Solids》2014
Polycrystalline thin films usually present magnetic anisotropy resulting from a conjunction of textures, residual stresses, surface effects, and magnetic dipole distribution. The shape anisotropy, which is caused by the magnetic dipole distribution, is dominant in most of the cases, and it forces the occurrence of in-plane easy axes for the magnetization. Contrary to this common expectation, we have found predominant out-of-plane easy axes in a series of Fe–Ni thin films produced by DC sputtering. Films with different thicknesses, from 40 to 1000 nm, and different deposition temperatures have been tested and show similar results. These unusual characteristics are results of a particular columnar structure formed during the films growth. The magnetic characterization of the samples has been done by Mössbauer spectroscopy, magnetometry, and ferromagnetic resonance. The unusual anisotropy observed is not believed to be uniform along the film thickness. This interpretation comes from the comparison of the experimental results with hysteresis obtained by micromagnetic simulations. Five distinct configurations for the anisotropies have been simulated for this comparison. 相似文献
8.
Kanji Shibagaki Kota Kawano Atsuto Mori 《Applied Physics A: Materials Science & Processing》2013,110(4):805-808
Shape-memory alloys are crucial in various industrial fields. However, a high-quality film synthesis method has not been established yet. Here we examine optimum conditions for synthesis of thin films by pulsed laser deposition of Ti–Ni alloy target in vacuum. We investigated surface morphologies and chemical compositions of the films which were obtained under various conditions. We found that the suitable Ti/Ni ratio was obtained by adjusting the distance between the target and the substrate in vacuum. In parallel, we analyzed plasma plume by optical emission spectroscopy and time-of-flight mass spectrometry. We discuss the basic behavior of ablated particles in vacuum. 相似文献
9.
A. Matei R. Birjega A. Vlad M. Filipescu A. Nedelcea C. Luculescu R. Zavoianu O.D. Pavel M. Dinescu 《Applied Surface Science》2012,258(23):9466-9470
Powdered layered double hydroxides (LDHs) have been widely studied due to their applications as catalysts, anionic exchangers or host materials for inorganic and/or organic molecules. Assembling nano-sized LDHs onto flat solid substrates forming thin films is an expanding area of research due to the prospects of novel applications as sensors, corrosion-resistant coatings, components in optical and magnetic devices.Continuous and adherent thin films were grown by laser techniques (pulsed laser deposition – PLD and matrix assisted pulsed laser evaporation – MAPLE) starting from targets of Mg–Al LDHs. The capacity of the grown thin films to retain a metal (Ni) from contaminated water has been also explored. The thin films were immersed in an Ni(NO3)2 aqueous solutions with Ni concentrations of 10?3% (w/w) (1 g/L) and 10?4% (w/w) (0.1 g/L), respectively. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) were the techniques used to characterize the prepared materials. 相似文献
10.
X.L. Tong K. Lin D.J. Lv M.H. Yang Z.X. Liu D.S. Zhang 《Applied Surface Science》2009,255(18):7995-7998
(1 ? x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) thin films have been deposited on quartz substrates using pulsed laser deposition (PLD). Crystalline microstructure of the deposited PMN–PT thin films has been investigated with X-ray diffraction (XRD). Optical transmission spectroscopy and Raman spectroscopy are used to characterize optical properties of the deposited PMN–PT thin films. The results show that the PMN–PT thin films of perovskite structure have been formed, and the crystalline and optical properties of the PMN–PT thin films can be improved as increasing the annealing temperature to 750 °C, but further increasing the annealing temperature to 950 °C may lead to a degradation of the crystallinity and the optical properties of the PMN–PT thin films. In addition, a weak second harmonic intensity (SHG) has been observed for the PMN–PT thin film formed at the optimum annealing temperature of 750 °C according to Maker fringe method. All these suggest that the annealing temperature has significant effect on the structural and optical properties of the PMN–PT thin films. 相似文献
11.
《Journal of magnetism and magnetic materials》1987,68(3):391-395
Noninduced uniaxial magnetic anisotropy in Fe1−xBx thin films of metallic glasses was studied for 26⩽x⩽32. The samples were obtained by rf sputtering technique. Thickness and compositional dependence of uniaxial magnetic anisotropy was determined for films with thickness d⩽120 nm. The existence of the uniaxial magnetic anisotropy can be explained roughly by a directional alignment of free volume and directional order of atomic pairs in the vicinity of the free volume. 相似文献
12.
J. Faupel C. Fuhse A. Meschede C. Herweg H.U. Krebs S. Vitta 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1233-1235
Ceramic–metal (MgO combined with Fe, Ti and Ni80Nb20) and polymer–metal (polycarbonate combined with Ag and Pd) nanocomposite multilayers were deposited at room temperature by laser ablation (at 248 nm). The multilayers were characterized by X-ray reflectometry, infrared spectroscopy and transmission electron microscopy. In the case of MgO/metal multilayers, well-layered structures are produced down to layer periodicities of 1.2 nm, necessary for tunneling magnetoresistance devices and X-ray mirrors in the water window. The interface roughness in the case of polymer/metal multilayers is found to be a strong function of the metal layer thickness and also the nature of the metal. PACS 68.55.-a; 81.15.Fg 相似文献
13.
H. Spillmann P.R. Willmott M. Morstein P.J. Uggowitzer 《Applied Physics A: Materials Science & Processing》2001,73(4):441-450
High-quality thin films of ZrN, ZrxAlyN and ZrxGayN have been grown by pulsed reactive crossed-beam laser ablation using Zr, Zr-Al and Zr-Ga ablation targets, respectively,
and a N2 gas pulse. The films were characterized for their chemical, crystallographic and tribological properties. All the films had
very low impurity levels and a cubic rock salt crystal structure over the entire investigated temperature range between room
temperature and 600 °C. High-quality epitaxial films could be grown on Si (001) at 400 °C, though the crystallinity was disrupted
at 525 °C by Si diffusion into the film bulk and the formation of ZrSi2 crystallites. Films grown on stainless steel were polycrystalline. The ratios of the metals in the alloy targets were in
general not equal to those in the films: the Al content in the ZrxAlyN films was lower than the target value, which we attribute to differential scattering in the ablation plume. The Ga content
in the ZrxGayN films fell with increasing substrate temperature, indicative of re-evaporation of Ga from the substrate surface. Those ZrxGayN films with the highest Ga content, grown at the lowest temperatures, were particularly nitrogen-deficient, which we attribute
to the low reactivity of Ga with N2. The ZrxAlyN films had an exceptionally low coefficient of friction (0.20) versus steel and the greatest nanohardness of 28 GPa.
Received: 9 November 2000 / Accepted: 14 November 2000 / Published online: 28 February 2001 相似文献
14.
《Journal of magnetism and magnetic materials》2001,231(1):85-93
The magnetic properties and microstructure of electrodeposited Ni–W thin films (0–11.7 at% W in composition) were studied. The film structures were divided into three regions: an FCC nanocrystalline phase (0–2 at% W), a transition region from FCC nanocrystalline to amorphous phase (2–7 at% W), and an amorphous phase (>7 at% W). In the transition region, (4–5 at% W) films with perpendicular magnetic anisotropy (PMA) were found. The saturation magnetization, magnetic anisotropy field, perpendicular magnetic anisotropy and perpendicular coercivity for a typical Ni–W film (4.5 at% W) were 420 kA/m, 451 kA/m, 230 kJ/m and 113 kA/m, respectively. The microstructure of Ni–W films with PMA is composed of isolated columnar crystalline grains (27–36 nm) with the FCC phase surrounded by the Ni–W amorphous phase. The appearance of the interface between the magnetic core of Ni crystalline grains and the Ni–W non-magnetic boundary layer seems to be the driving mechanism for the appearance of PMA. The origin of PMA in Ni–W films is mainly attributed to the magnetoelastic anisotropy associated with in-plane internal stress and positive magnetostriction. The secondary source of PMA is believed to be the magnetocrystalline anisotropy of 〈1 1 1〉 columnar grains and its shape magnetic anisotropy. It is concluded that Ni–W electrodeposited films (4–5 at% W) may be applicable for perpendicular magnetic recording media. 相似文献
15.
Virginie Monnier Maria Bacia Jean-Luc Putaux Alain Ibanez 《Journal of nanoparticle research》2008,10(1):129-139
The tetracene molecule (2,3-benzanthracene, C8H12) was used to synthesize nanocrystals grown in sol–gel thin films, ranging from 10 to 100 nm of diameter. This confined nucleation
and growth was compared to microcrystallizations of the same molecule in free solution. Transmission electron microscopy (TEM)
was used to characterize these two kinds of tetracene crystals. The observation was performed under low-dose illumination
to avoid amorphization of the samples during electron irradiation. Spatial confinement and size distribution of micro- and
nanocrystals were compared. Using electron microdiffraction and diffraction patterns simulations, we showed that free microcrystals
and nanocrystals confined in gel glasses exhibit the same triclinic
structure. In addition, time-resolved spectroscopy was used to record fluorescence decays, showing a monoexponential fluorescence
decay for nanocrystals while microcrystals exhibit a multiexponential decay. The simple signature of nanocrystals luminescence
is promising for the future development of chemical or biological sensors. 相似文献
16.
WANG Xiaodong PENG Xiaofeng & ZHANG Duanming Laboratory of Phase Change Interfacial Transport Phenomena Department of Thermal Engineering Tsinghua University Beijing China Department of Physics Huazhong University of Science Technology Wuhan China 《中国科学G辑(英文版)》2005,48(1):33-43
Using the Sol-Gel method to produce the KTN ultrafine powder and the sintering technique with K2O atmosphere to prepare KTN ceramics as the targets instead of the KTN single crystal, highly oriented KTN thin films were produced on the transparent single crystal quartz (100) by the pulsed laser deposition (PLD). Since the thermal stress sustained by the quartz is relatively small, the limit temperature of the quartz substrates (300℃) is much lower than that of the P-Si substrates (560℃); the prepared thin film is at amorphous state. Increasing the pulsed laser energy density in the process incorporated with annealing the film after deposition at different temperatures converts the amorphous films into crystal. The optimal pulsed laser energy density and annealing temperature were 2.0 J/cm2 and 600℃, respectively. A discussion was made to understand the mechanism of film production at relatively low substrate temperature by PLD and effects of the annealing temperatures on the forming of the perovskite p 相似文献
17.
I. Hanyecz J. Budai A. Oszkó E. Szilágyi Z. Tóth 《Applied Physics A: Materials Science & Processing》2010,100(4):1115-1121
Amorphous silicon–carbon alloy films in different compositions were prepared by pulsed laser deposition from two-component
targets containing pure silicon and carbon parts. The silicon–carbon ratio in the films was varied by adjusting the number
of laser shots on the constituent silicon and carbon targets. The composition, optical properties, thickness, and bonding
structure of the films were determined by backscattering spectrometry, spectroscopic ellipsometry, and X-ray photoelectron
spectroscopy, respectively. Backscattering spectrometry data were used to determine the deposition rate of silicon and carbon.
This enabled the calculation of the number of the shots onto each target to reach a predefined composition. As the film composition
changed from carbon to silicon, it was shown that the microscopic and macroscopic properties of the films also changed from
a diamond-like carbon phase to an amorphous silicon phase via graphite- and silicon-carbide-like composite. 相似文献
18.
Sava? S?nmezo?lu Güven ?ankaya Necmi Serin 《Applied Physics A: Materials Science & Processing》2012,107(1):233-241
Nanostructured TiO2 thin films were deposited on quartz glass at room temperature by sol–gel dip coating method. The effects of annealing temperature
between 200∘C to 1100∘C were investigated on the structural, morphological, and optical properties of these films. The X-ray diffraction results
showed that nanostructured TiO2 thin film annealed at between 200∘C to 600∘C was amorphous transformed into the anatase phase at 700∘C, and further into rutile phase at 1000∘C. The crystallite size of TiO2 thin films was increased with increasing annealing temperature. From atomic force microscopy images it was confirmed that
the microstructure of annealed thin films changed from column to nubbly. Besides, surface roughness of the thin films increases
from 1.82 to 5.20 nm, and at the same time, average grain size as well grows up from about 39 to 313 nm with increase of the
annealing temperature. The transmittance of the thin films annealed at 1000 and 1100∘C was reduced significantly in the wavelength range of about 300–700 nm due to the change of crystallite phase. Refractive
index and optical high dielectric constant of the n-TiO2 thin films were increased with increasing annealing temperature, and the film thickness and the optical band gap of nanostructured
TiO2 thin films were decreased. 相似文献
19.
G. Wang O. Marty C. Garapon A. Pillonnet W. Zhang 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1599-1602
-Al2O3 films doped with about 1% Eu3+ were grown on sapphire (012) substrates by pulsed laser deposition using an ArF excimer laser under 10-4 mbar oxygen pressure and at temperatures higher than 1050 °C. The Eu doping rate was measured by Rutherford backscattering spectroscopy. The crystalline structure was determined by X-ray diffraction and transmission electron microscopy. The films are grown epitaxially on the sapphire substrate. The Eu3+ fluorescence spectra are constituted of narrow lines. By means of pulsed laser deposition, Eu3+ ions may be introduced into a single site of the -phase lattice, with a concentration that cannot be reached using conventional crystal-growth methods. PACS 81.15.Fg; 68.37.Lp; 78.55.Hx 相似文献
20.
Britta Fuchs Felix Schlenkrich Susanne Seyffarth Andreas Meschede Robert Rotzoll Philipp Vana Peter Gro?mann Klaus Mann Hans-Ulrich Krebs 《Applied Physics A: Materials Science & Processing》2010,98(4):711-715
Smooth poly(methyl methacrylate) (PMMA) films without any droplets were pulsed laser deposited at a wavelength of 248 nm and
a laser fluence of 125 mJ/cm2. After deposition at room temperature, the films possess low universal hardness of only 3 N/mm2. Thermal treatments up to 200°C, either during deposition or afterwards, lead to film hardening up to values of 200 N/mm2. Using a combination of complementary methods, two main mechanisms could be made responsible for this temperature induced
hardening effect well above the glass transition temperature of 102°C. The first process is induced by the evaporation of
chain fragments and low molecular mass material, which are present in the film due to the ablation process, leading to an
increase of the average molecular mass and thus to hardening. The second mechanism can be seen in partial cross-linking of
the polymer film as soon as chain scission occurs at higher temperatures and the mobility and reactivity of the polymer material
is high enough. 相似文献