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1.
D. Langevin 《The European physical journal. E, Soft matter》2001,5(1):81-85
Studies of thin liquid films, made from semidilute polyelectrolyte solutions, are presented. The disjoining pressure variation
with film thickness exhibits oscillations, corresponding to film stratification. The oscillations become sharper as the polymer
concentration c increases, and disappear when salt is added. The period of the oscillations scales as c
-1/2. The observed stratification is related to the polymer network and the size of the steps to the mesh size ξ.
Received 25 April 2000 and Received in final form 3 October 2000 相似文献
2.
Ngai KL 《The European physical journal. E, Soft matter》2002,8(2):225-235
Large increases of mobility of local segmental relaxation observed in polymer films as the film thickness is decreased, as
evidenced by decreases of the glass temperature, are not found for relaxation mechanisms that have longer length scales including
the Rouse relaxation modes and the diffusion of entire polymer chains. We show that the coupling model predictions, when extended
to consider polymer thin films, are consistent with a large increase of the mobility of the local segmental motions and the
lack of such a change for the Rouse modes and the diffusion of entire polymer chains. There are two effects that can reduce
the coupling parameter of the local segmental relaxation in thin films. One is the chain orientation that is induced parallel
to the surface when the film thickness h becomes smaller than the end-to-end distance of the chains and the other is a finite-size effect when h is no longer large compared to the cooperative length scale. Extremely thin ( ≈ 1.5 nm) films obtained by intercalating a
polymer into layered silicates have thickness significantly less than the cooperative length scale near the bulk polymer glass
transition temperature. As a result, the coupling parameter of the local segmental relaxation in such thin films is reduced
almost to zero. With this plausible assumption, we show the coupling model can explain quantitatively the large decrease of
the local segmental relaxation time found experimentally.
Received 1 August 2001 and Received in final form 1 December 2001 相似文献
3.
A. Aradian E. Raphaël P.G. de Gennes 《The European physical journal. E, Soft matter》2000,2(4):367-376
We consider a porous solid covered with a water film (or with a drop) in situations where the liquid is pumped in, either
spontaneously (if the porous medium is hydrophilic) or mechanically (by an external pump). The dynamics of dewetting is then
strongly modified. We analyse a few major examples, a) horizontal films, which break at a certain critical thickness, b) the
“modified Landau-Levich problem” where a porous plate moves up from a bath and carries a film: aspiration towards the plate
limits the height H reached by the film, c) certain situation where the hysteresis of contact angles is important.
Received 5 October 1999 and Received in final form 7 February 2000 相似文献
4.
We discuss the adsorption of polymer gels on flat surfaces. Even in cases of complete wetting where the spreading power S is positive and where an equivalent liquid would spread, the elastic stresses due to the gel deformation upon adsorption
oppose the spreading. The competition between elasticity characterized by the bulk shear modulus G and capillarity characterized by the spreading power S defines a typical length scale ℓ = S/G for the deformation in the gel. For loose gels ℓ can be of the order of 1 μm. Macroscopic gels larger than ℓ deform only
at their edges over a region of size ℓ. Microscopic gels smaller than ℓ show a finite deformation despite the elastic stresses.
The elastic stresses limit the spreading of the polymer, but solvent can be sucked out of a swollen gel by wetting the surface.
The thin solvent film can extend rather far from the gel edge and carry solvent. We calculate the kinetics of the solvent
film formation and of the solvent transfer from a more swollen gel to a less swollen gel.
Received 16 July 2001 相似文献
5.
R. Rössler J.D. Pedarnig D. Bäuerle E.J. Connolly H.W. Zandbergen 《Applied Physics A: Materials Science & Processing》2000,71(3):245-247
Thin films of Bi2Sr2CaCu2O8+δ have been grown on vicinal (001) SrTiO3 substrates by pulsed-laser deposition. Transmission electron microscopy (TEM) and X-ray diffraction reveal well ordered films
with the c axis of the film parallel with the c axis of the substrate for miscut angles up to θS≈15°. TEM also reveals the step-like film morphology due to step-flow growth. The in-plane and out-of-plane resistivities
are independent of film thickness within the range 20–300 nm and agree quite well with Bi2Sr2CaCu2O8+δ single-crystal data.
Received:15 May 2000 / Accepted:17 May 2000 / Published online: 9 August 2000 相似文献
6.
Linear and nonlinear absorptance in Al2O3 films of different optical thicknesses are investigated using an ArF laser calorimeter. While the linear absorptance at 193
nm shows the expected linear increase, nonlinear absorptance increases quadratically with increasing film thickness. Thus,
it cannot be described by a constant nonlinear absorption coefficient β. The experimental findings are explained by a simple
phenomenological approach using excited states with a finite interaction length longer than the actual film thickness. a new
material constant Γ is introduced, which describes the nonlinear absorptance behavior correctly.
Received: 19 May 2000 / Accepted: 22 May 2000 / Published online: 13 July 2000 相似文献
7.
Universal non-monotonic smectic fluctuations of liquid crystal films in a magnetic field 总被引:1,自引:0,他引:1
I.N. de Oliveira M.L. Lyra 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):189-194
Free-standing liquid crystal films with positive diamagnetic susceptibility can have the smectic ordering enhanced by an external
field applied perpendicular to the plane layers. Within a quadratic functional integral approach, we investigate the interplay
between the smectic order induced by an external field H and that due to the surface tension γ between the film and the surrounding gas. We find that the average smectic fluctuation
is a non-monotonic function of film thickness, with a characteristic thickness scale ξ
H delimiting the predominance of surface tension and magnetic field effects. This characteristic thickness obeys simple asymptotic
power-law relations as a function of the ordering terms which allows us to represent the average smectic fluctuations in a
universal scaling form.
Received 7 January 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: marcelo@ising.fis.ufal.br 相似文献
8.
N. Rehse C. Wang M. Hund M. Geoghegan R. Magerle G. Krausch 《The European physical journal. E, Soft matter》2001,4(1):69-76
We study the wetting behaviour of thin polystyrene (PS) films on regularly corrugated silicon substrates. Below a critical
film thickness the PS films are unstable and dewet the substrates. The dewetting process leads to the formation of nanoscopic
PS channels filling the grooves of the corrugated substrates. Films thicker than the critical thickness appear stable and
follow the underlying corrugation pattern. The critical thickness is found to scale with the radius of gyration of the unperturbed
polymer chains.
Received 6 April 2000 and Received in final form 24 August 2000 相似文献
9.
H. Beckmann G. Bergmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):495-502
Sandwiches made from Fe and Cs films are investigated as a function of the magnetic field and the Cs thickness. Conduction
electrons which cross from the Fe to the Cs are marked by a drift velocity component perpendicular to the electric field.
The anomalous Hall effect in the Fe provides this “non-diagonal” kick to the electrons that cross from the Fe into the Cs.
The ballistic propagation of the conduction electrons can be monitored as a function of the Cs film thickness. The free propagation
into the Cs is measured in terms of the non-diagonal conductance Lxy which we denote as the “induced anomalous Hall conductance”L
xy
0. For a normal (non-magnetic) metal in contact with Fe, Lxy increases with the thickness of the normal metal until the film thickness exceeds (half) the mean free path of the conduction
electrons. For Cs on top of Fe the induced anomalous Hall conductance increases up to a Cs coverage of about 100 A, then,
in contrast to other non-magnetic metals, L
xy
0 decreases for larger Cs coverage and approaches zero. This behavior cannot be explained with the free electron model. The
strange behavior of the induced AHC in Cs films adds an even more challenging mystery to the already poorly understood properties
of thin Cs films. These results defy explanation in the free electron model.
Received 29 April 1999 and Received in final form 10 July 1999 相似文献
10.
A. Albersdörfer E. Sackmann 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):663-672
In this paper we study the effect of monovalent and divalent ions on the swelling behavior and viscoelastic parameters of ultrathin layers of the natural polyelectrolyte hyaluronic acid
covalently coupled to glass substrates. A colloidal probe technique is applied for this purpose based on latex beads, hovering over the polymer cushion. By analyzing the vertical Brownian motion of these beads with reflection
interference contrast microscopy (RICM) we determined the equilibrium layer thickness (with 3 nm vertical resolution), the
interfacial interaction potential, and the characteristic mesh size limiting the hydrodynamic flow within the polyelectrolyte
film as a function of the ionic strength. The experimental results are interpreted in terms of three different theoretical
models: the polyelectrolyte brush approximation of Pincus [#!ref1!#], a modified polyelectrolyte brush approximation in the
high salt concentration limit of Ross and Pincus [#!ref2!#] and the simple scaling approximation for neutral adsorbed polymers
of de Gennes [#!ref3!#]. Within experimental error all of these different models fit our experimental data and yield comparable
results for the equilibrium layer thickness. Moreover we determine a thickness dependent, effective surface coverage from
both brush models. The hydrodynamic properties of the films are interpreted in terms of the Brinkmann model of elastic porous
media by assuming an effective mesh size, which depends linearly on the Debye screening length. The salt induced condensation
of the polyelectrolyte films can be described microscopically in terms of a progressive contraction of the mesh size with
increasing salt concentration.
Received 10 September 1998 and Received in final form 30 November 1998 相似文献
11.
M.I. Marqués J.A. Gonzalo 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):317-321
The Monte Carlo (MC) approach is used to check the validity of the scaling relationship for the effective critical exponents in thin Ising films. We investigate this relationship not just in the critical region
but throughout the crossover to the expected two-dimensional behavior. Our results indicate that this scaling relationship
is very well-fulfilled throughout the entire crossover temperature region, as predicted by a previous renormalization group
analysis. The two-dimensional universality class of Ising films is confirmed by means of data collapsing plots for plates with increasing L, up to L=100. The evolution of the maximum value of the effective critical exponents with film thickness is discussed.
Received 22 April 1999 相似文献
12.
E.M. de Sousa Luz A.F. Siqueira U.M.S. Costa M.L. Lyra 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):115-118
The recent improvements on the technology for developing high-quality thin magnetic films has renewed the interest in the
study of surface effects in both static and dynamic magnetic responses. In this work, we use a Monte-Carlo algorithm with
Metropolis dynamics together with a spreading of damage technique to study the interplay between the effects of finite thickness
and surface ordering field in thin ferromagnetic Ising (S=1/2) films. We calculate, near the bulk critical temperature and several values of the surface field, the dependence on the
film thickness of the average magnetization M and Hamming distance D. We employ a finite size scaling analysis to show that both obey an effective one-parameter scaling but exhibit distinct
characteristic surface fields. At their corresponding characteristic surface fields both M and D become roughly thickness independent and we estimate the critical exponent characterizing the behavior of the typical scaling
lengths.
Received 29 March 1999 and Received in final form 21 April 1999 相似文献
13.
Chord length distributions describe size, shape and spatial arrangement of geometrical objects (particles). The chord length
distribution is in principle proportional to the second derivative of the correlation function of small-angle scattering.
It is calculable from a relative measurement of the scattering intensity I(h). In structure research, the characterization of numerous particle systems can be achieved by comparing experimental chord
distributions with theoretical ones, provided the latter are available with sufficiently high precision for a lot of fundamental,
universal shapes. Both sides of this concept are exemplified: – the step from a relative measurement of the scattering intensity
of an isotropic two-phase sample to the chord length distribution (errors in and in , limited h-interval, corresponding to the region (1-2) nm < r in real space, must be observed); as well as the geometric matter of calculation of chord distributions as fingerprints for
basic geometric figures, including the non-convex case.
Received 15 March 1999 and Received in final form 26 April 2000 相似文献
14.
Hartmann L Gorbatschow W Hauwede J Kremer F 《The European physical journal. E, Soft matter》2002,8(2):145-154
The molecular dynamics in thin films (18 nm-137 nm) of isotactic poly(methyl methacrylate) (i-PMMA) of two molecular weights
embedded between aluminium electrodes are measured by means of dielectric spectroscopy in the frequency range from 50 mHz
to 10 MHz at temperatures between 273 K and 392 K. The observed dynamics is characterized by two relaxation processes: the
dynamic glass transition (α-relaxation) and a (local) secondary β-relaxation. While the latter does not depend on the dimensions
of the sample, the dynamic glass transition becomes faster (≤2 decades) with decreasing film thickness. This results in a
shift of the glass transition temperature T
g to lower values compared to the bulk. With decreasing film thickness a broadening of the relaxation time distribution and
a decrease of the dielectric strength is observed for the α-relaxation. This enables to deduce a model based on immobilized
boundary layers and on a region displaying a dynamics faster than in the bulk. Additionally, T
g was determined by temperature-dependent ellipsometric measurements of the thickness of films prepared on silica. These measurements
yield a gradual increase of T
g with decreasing film thickness. The findings concerning the different thickness dependences of T
g are explained by changes of the interaction between the polymer and the substrates. A quantitative analysis of the T
g shifts incorporates recently developed models to describe the glass transition in thin polymer films.
Received 12 August 2001 and Received in final form 16 November 2001 相似文献
15.
C. Binns S.H. Baker M.J. Maher S.C. Thornton S. Louch S.S. Dhesi N.B. Brookes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):189-192
A portable UHV-compatible gas aggregation cluster source, capable of depositing clean mass-selected nanoclusters in situ, has been used at synchrotron radiation facilities to study the magnetic behaviour of exposed and Co-coated Fe clusters in
the size range 250 to 540 atoms. X-ray magnetic circular dichroism (XMCD) studies of isolated and exposed 250-atom clusters
show a 10% enhancement in the spin magnetic moment and a 75% enhancement in the orbital magnetic moment relative to bulk Fe.
The spin moment monotonically approaches the bulk value with increasing cluster size but the orbital moment does not measurably
decay till the cluster size is above ∼ 400 atoms. The total magnetic moments for the supported particles though higher than
the bulk value are less than those measured in free clusters. Coating the deposited particles with Co in situ increases the spin moment by a further 10% producing a total moment per atom close to the free cluster value. At low coverages
the deposited clusters are super-paramagnetic at temperatures above 10 K but a magnetic remanence at higher temperature emerges
as the cluster density increases and for cluster films with a thickness greater than 50 ?(i.e. 2-3 layers of clusters) the remanence becomes greater than that of an Fe film of the same thickness produced by a conventional
deposition source. Thick cluster-assembled film show a strong in-plane anisotropy.
Received 14 December 2000 相似文献
16.
A. Li Bassi C.E. Bottani B.K. Tanner A. Stella P. Tognini P. Cheyssac R. Kofman 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):31-38
The abrupt change of velocity in surface acoustic waves in thin films of amorphous SiOx containing nanometre scale -Sn crystals is shown to be directly associated with the size-dependent melting of the nanoparticles, confirming preliminary
experiments. High resolution thin film powder diffraction using synchrotron radiation shows that the abrupt redshift in the
Brillouin spectra satellites occurs at the same temperature as the melting of the nanoparticles, evident for the loss of the
Bragg peaks. Effective medium theory is used to explain the origin of the anomaly. A central peak in the Brillouin spectrum,
the intensity of which shows a maximum at the melting temperature, can be interpreted in terms of overdamped fluctuations
in the dielectric function. The melting temperature as a function of particle size is in agreement with theoretical predictions.
No evidence for strain could be found on the X-ray diffraction profiles; the a- and c-axis thermal expansion coefficients are the same as those in bulk tin.
Received 30 March 2000 and Received in final form 24 July 2000 相似文献
17.
A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase
fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C–H stretching band of vapor
n-decane and liquid n-dodecane near 3.4 μm (3000 cm−1). n-Dodecane film thicknesses <20 μm were accurately measured in the absence of vapor, and simultaneous measurements of n-dodecane liquid film thickness and n-decane vapor mole fraction (300 ppm) were measured with <10% uncertainty for film thicknesses <10 μm. A potential application
of the measurement technique is to provide accurate values of vapor mole fraction in combustion environments where strong
absorption by liquid fuel or oil films on windows make conventional direct absorption measurements of the gas problematic. 相似文献
18.
Laser-induced periodic surface structures (LIPSS) were generated on oriented and amorphous thick, as well as on spin-coated
thin, poly-carbonate films by polarized ArF excimer laser light. The influence of the film structure and thickness on the
LIPSS formation was demonstrated. Below a critical thickness of the spin-coated films the line-shaped structures transformed
into droplets. This droplet formation was explained by the laser-induced melting across the whole film thickness and subsequent
de-wetting on the substrate. The thickness of the layer melted by laser illumination was computed by a heat-conduction model.
Very good agreement with the critical thickness for spin-coated films was found. The original polymer film structure influences
the index of refraction of the thin upper layer modified by the laser treatment, as was proven by the dependence of the structure’s
period on the angle of incidence both for ‘s’- and ‘p’-polarized beams. The effect of the original surface roughness – grains in thick films or holes in thin films –
was studied using atomic force microscopy. It was shown that the oblique incidence of ‘s’-polarized beams results in an intensity confinement in the direction of the forward scattering and in asymmetrical interference
pattern formation around these irregularities. A new, two-dimensional grating-like structure was generated on spin-coated
films. These gratings might be used as a special kind of mask.
Received: 10 July 2001 / Accepted: 23 July 2001 / Published online: 30 August 2001 相似文献
19.
We study the technique of nanoindentation hardness measurement applied to extremely hard and elastic thin films. We do the
study with the aid of Hertz’s solutions for elastic contacts. The effect of different apical angles in ideally sharp conical
diamond indenters is analyzed. In addition, the blunt tip shape of practical diamond indenters is discussed. The area function
of the tip of real indenters is deduced from experimental nanoindentation measurements performed with these indenters on fused
quartz. Triangular-base pyramidal indenters with Berkovich and cube corner geometries are considered. Theoretical hardness
values applying Hertz’s and Oliver and Pharr’s methods of analysis are obtained and compared with the experimental data deduced
from nanoindentation measurements performed on very hard and elastic ta-C films. The theoretical analysis shows a necessary
dependence of the calculated hardness values with the apical angle of the indenter in totally elastic materials and to some
extent in elastoplastic materials. Moreover, when the indenter tip is blunt or when there are inaccuracies in the measured
area function of the indenter tip, hardness values decrease for very small penetration depths. Besides, in these films, because
of their very small thickness, measured hardness values also decrease for measurements with penetration depths larger than
a fraction of film thickness, due to the effects of the softer substrate.
Received: 13 June 2000 / Accepted: 21 June 2000 / Published online: 5 October 2000 相似文献
20.
P.G. de Gennes 《The European physical journal. E, Soft matter》2000,2(3):201-205
Freely standing polystyrene films show an anomalous drop of the glass temperature when the molecular weight is high and the thickness smaller than the coil size R0. We present here a tentative explanation for these features, where two types of motions compete: a) standard motions, controlled
by the free volume, and independent of chain length, b) collective motions along the chain, which require a weaker free volume
(except for the end groups). For bulk systems, the standard motion always wins because of the end group hindrance. But for
films thinner than the coil size, the dominant process may be the collective motion of a “loop” which does not involve the
chain ends. What matters then is not the overall polymerisation index (N), but the length g of a typical loop starting from the surface (which is a more fluid region) and reaching deep into the film. With these ingredients,
some surprising aspects of may possibly be understood.
Received 7 December 1999 相似文献