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1.
Valov P. M. Le?man V. I. Maksimov M. V. Derkacheva O. Yu. 《Physics of the Solid State》2010,52(4):821-825
The changes observed in the kinetics of CuCl nucleation in glass due to preliminary low-temperature annealing have been investigated
using optical spectroscopy. The influence of the number of nuclei formed at a temperature of 500°C on the growth rate of the
CuCl phase at 650°C has been examined. The amount of the CuCl phase in the sample is determined from the optical absorption
coefficient in the range of band-to-band transitions in the CuCl nanocrystals. The average radius of CuCl particles is calculated
from the position of the maximum of the exciton band. It has been demonstrated that the preliminary formation of CuCl nuclei
at 500°C for 3 h makes it possible to increase the growth rate of the CuCl phase by a factor of 6. In the sample with preliminarily
formed nuclei, there occur two opposite processes: thermal decomposition of part of the small nuclei, which have become subcritical
at 650°C; and the growth of larger nuclei, which have become supercritical at 650°C due to the diffusive inflow of the components
of the new phase. When the equilibrium concentration is reached, the new phase contains particles with a smaller radius but
at a higher concentration as compared to those in the case of the conventional nucleation at 650°C. 相似文献
2.
P. M. Valov V. I. Leiman O. Yu. Derkacheva V. M. Maksimov E. S. Markov 《JETP Letters》2012,95(5):249-252
Processes of the formation of the double distribution of CuCl nanoparticles in glass in two-stage annealing have been analyzed.
The distribution of CuCl nanoparticles with the average radius R
1 = 14 and 18 nm appears in 20 and 40 min at temperature T
1 = 700°C in samples 1 and 2, respectively. By this time, the formation of new clusters ends, and only the growth of previously
formed clusters occurs (the second stage of nucleation). Then, the formation of the CuCl phase continues at T
2 = 500°C. A decrease in the temperature is accompanied by a decrease in the critical radius of particles of a new phase. For
this reason, the formation and growth of new CuCl nuclei begin again and the second distribution with a mean radius of 1 nm
or larger is formed. As a result, double distributions of CuCl nanoparticles with significantly different mean radii are formed
in samples 1 and 2. The concentration and mean radius of CuCl particles in distributions have been determined from the optical
absorption spectra of CuCl nanocrystals at 80 K in the wavelength range of 300–500 nm. 相似文献
3.
V. I. Leiman P. M. Valov V. M. Maksimov O. Yu. Derkacheva E. S. Markov 《Physics of the Solid State》2013,55(6):1252-1257
The processes of nucleation in a CuCl solid solution in glass with a positive temperature jump from T 1 = 500°C to T 2 = 550, 600, and 650°C have been investigated using optical spectroscopy and exciton-thermal analysis. The dissolution of a part of the particles of the CuCl nanomelt formed previously at T 1 has been observed at T 2. Variations in the shape of the radius distribution curve of the CuCl particles due to the dissolution of initial nuclei have been determined from the melting kinetics of CuCl particles during linear heating of the sample. The nonisothermal nucleation of CuCl in glass under conditions of the temperature jump has been simulated numerically. The results of calculations of the variations in the radius distribution of CuCl particles are in agreement with the experiment. The calculated data on the variation in time of the critical radius r c and the concentration of CuCl monomers in glass after the temperature jump have been obtained. 相似文献
4.
The fundamental absorption spectra of CuCl nanocrystals in glass samples are investigated in the energy range 3–4 eV at a temperature of 300 K with the aim of elucidating the kinetics of the initial stage of the formation of the CuCl phase in the glass. The CuCl phase is grown in the glass under stepwise annealing at temperatures of 500, 615, and 707°C. The kinetics of variation in the intensity and the shift of the maximum in the exciton absorption spectra of CuCl nanocrystals are studied in the course of annealing of the glass samples. It is established that, for all the temperatures under investigation, the formation of the CuCl phase begins with the transient stage that involves the fluctuation formation of supercritical nuclei of the CuCl nanomelt. At a temperature of 500°C, the transient stage gives way to the stage of a rapid increase in the number of supercritical nuclei of the CuCl phase. At temperatures of 615 and 707°C, the transient stage gives way to the stage of an intensive growth of nuclei without a considerable increase in their number. The number of nuclei formed during the transient stage at 707°C is smaller than that observed after the transient stage at 500°C by a factor of 24. However, the sizes of the nuclei formed at 707°C are larger than those observed after the transient stage at 500°C. This difference is explained by the fact that the diffusion length of Cu+ ions controlling the formation of the CuCl phase increases with increasing temperature. The experimental data on the kinetics of the formation of the new phase in the glass are in good agreement with the Zel’dovich-Frenkel classical theory of the formation of a new phase, which accounts for the stage of the formation of critical nuclei. 相似文献
5.
The time variation and temperature dependence of a CuCl phase nucleation in a glass was studied by exciton spectroscopy. The phase formation kinetics at three temperatures was measured. A time delay in attaining a stationary rate of the new phase growth was observed at all temperatures, in agreement with the Zeldovich theory. The kinetic parameters of the CuCl phase formation were determined in the initial stage, when the critical nuclei possessing a zero surface energy (and an effective radius below 1.3 nm) appear in the glass matrix. The first-order phase transition in the new phase is 200 K below the melting temperature of CuCl single crystals. The temperature dependence of the CuCl phase nucleation rate reveals the second and third stages of the new phase formation. The activation energies for diffusion of the CuCl phase components in the glass matrix are determined. 相似文献
6.
V. I. Leiman P. M. Valov V. M. Maksimov O. Yu. Derkacheva E. S. Markov 《Physics of the Solid State》2013,55(6):1258-1261
The processes of nonisothermal nucleation in the CuCl solid solution in glass with a negative jump of the nucleation temperature have been investigated using optical spectroscopy and exciton-thermal analysis. Two distributions of CuCl nanoparticles differing in the average radii R (2.3 and 14.0 nm) have been obtained for the temperature drop from T 1 = 700°C to T 2 = 500°C. The formation of two distributions of CuCl particles has been numerically simulated and the agreement between the experimental and calculated radius distributions of CuCl particles has been obtained. 相似文献
7.
In glass, the CuCl phase starts to form a certain time after the onset of supersaturation. As the temperature is increased, the transient period (stage of formation of critical nuclei) shortens and the growth kinetics of the CuCl phase switches from the first to second stage. The observed pattern of the CuCl phase growth kinetics is fully consistent with the Zel’dovich-Frenkel classical theory of new-phase formation. The delay time is determined by the radius of the critical nucleus (CuCl nanomelt) and the diffusion coefficient of the limiting component, the Cu+ ions. The radius of the critical nucleus is about 1 nm and does not vary within a broad temperature range. The activation energy for the CuCl phase growth process does not change in the transition from the formation of critical nuclei to the first and, subsequently, second stage. 相似文献
8.
The absorption spectra and the melting and crystallization kinetics of CuCl nanocrystals in glass are investigated in the
range of particle radii 1–30 nm. Three discontinuities are found on the curves representing the size dependence of the melting
point T
m(R) and the crystallization point T
c(R). As the particle radius gradually decreases from 30 nm in the range R⩽12.4 nm there is a sudden 60° drop in the temperature T
c in connection with the radius of the critical CuCl nucleus in the melt. A 30° drop in T
m is observed at R=2.1 nm, and a second drop of 16° in the temperature T
c is observed for CuCl particles of radius 1.8 nm. The last two drops are associated with changes in the equilibrium shape
of the nanoparticles. In the range of smaller particles, R⩽1.34 nm the T
c(R) curve is observed to merge with the T
m(R) curve, owing to the disappearance of the work of formation of the crystal surface during crystallization of the melt as
a result of the zero surface tension of CuCl particles of radii commensurate with the thickness of the effective surface layer.
An increase in the size shift of the exciton energy is observed in this same range of CuCl particle radii (1–1.8 nm). The
size dependence of the melting and crystallization temperatures of the nanoparticles is attributed to variation of the free
energy in the surface layer of a particle.
Fiz. Tverd. Tela (St. Petersburg) 41, 310–318 (February 1999) 相似文献
9.
Pencer J Mills T Anghel V Krueger S Epand RM Katsaras J 《The European physical journal. E, Soft matter》2005,18(4):447-458
Using coarse grained models of heterogeneous vesicles we
demonstrate the potential for small-angle neutron scattering
(SANS) to detect and distinguish between two different categories
of lateral segregation: 1) unilamellar vesicles (ULV) containing a
single domain and 2) the formation of several small domains or
“clusters” (~10 nm in radius) on a ULV. Exploiting the
unique sensitivity of neutron scattering to differences between
hydrogen and deuterium, we show that the liquid ordered (lo)
DPPC-rich phase can be selectively labeled using chain deuterated
dipalymitoyl phosphatidylcholine (dDPPC), which greatly
facilitates the use of SANS to detect membrane domains. SANS
experiments are then performed in order to detect and
characterize, on nanometer length scales, lateral heterogeneities,
or so-called “rafts”, in ~30 nm radius low polydispersity
ULV made up of ternary mixtures of phospholipids and cholesterol.
For 1:1:1 DOPC:DPPC:cholesterol (DDC) ULV we find evidence for the
formation of lateral heterogeneities on cooling below 30 °C. These heterogeneities do not appear when DOPC is
replaced by SOPC. Fits to the experimental data using coarse
grained models show that, at room temperature, DDC ULV each
exhibit approximately 30 domains with average radii of ~10 nm. 相似文献
10.
In this study, the influence of post-deposition annealings (PDA) up to temperatures of T
PDA=700°C on the room-temperature resistivity of e-beam evaporated titanium/platinum (Ti/Pt) bi-layers on low temperature co-fired
(LTCC) substrates covered with a glass encapsulate is investigated. The thickness of the platinum top layer is varied between
24 and 95 nm (titanium film thickness: 5 nm) and between 23 and 90 nm (titanium film thickness: 15 nm), respectively. In the
“as-deposited” state and up to post-deposition annealing temperatures of T
PDA=450°C, the film resistivity is linearly correlated with the reciprocal value of the platinum film thickness according to
the size effect. When applying, however, solely the Fuchs-Sondheimer model for evaluation, the effective mean free path for
electrons is substantially above the value reported for crystalline platinum at room temperature. Compared to similar investigations
on smooth Si/SiO2 substrates yielding interpretable results within this theoretical approach, this is due to the increase of the thickness-dependent
fraction in film resistivity which is strongly affected by the enhanced LTCC/glass surface roughness. At T
PDA>600°C, diffusion of titanium into the platinum top layer and the roughening of the LTCC/glass substrate dominate the electrical
behavior, both causing an increase in film resistivity above average. In contrast to Si/SiO2 substrates, thermal induced grooving effects in the Pt top layer play a minor role as the temperature coefficients of expansion
of metallization and glass-ceramic substrate match better and the effective temperature difference for stress generation is
lower due a glass softening temperature of about 450°C. 相似文献
11.
W. Deng T. Ohgi H. Nejo D. Fujita 《Applied Physics A: Materials Science & Processing》2001,72(5):595-601
Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass
and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95%
indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements
were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal
annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions
and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range
3.0–5.7×10-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities
in the range 2.9–4.0×10-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive
and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental
measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve
with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C,
and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films
still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in
air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces
were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h.
Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent
properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the
phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing
time have been investigated.
Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001 相似文献
12.
Yu. Kh. Vekilov I. A. Gordeev É. I. Isaev 《Journal of Experimental and Theoretical Physics》1999,89(5):995-999
The electronic spectrum and wave functions of a new quasicrystal structure—a two-dimensional Fibonacci lattice—are investigated
in the tight-binding approximation using the method of the level statistics. This is a self-similar structure consisting of
three elementary structural units. The “central” and “nodal” decoration of this structure are examined. It is shown that the
electronic energy spectrum of a two-dimensional Fibonacci lattice contains a singular part, but in contrast to a one-dimensional
Fibonacci lattice the spectrum does not contain a hierarchical gap structure. The measure of allowed states (Lebesgue measure)
of the spectrum is different from zero, and for “central” decoration it is close to 1. The character of the localization of
the wave functions is investigated, and it is found that the wave functions are “critical.”
Zh. éksp. Teor. Fiz. 116, 1834–1842 (November 1999) 相似文献
13.
L. S. Schulman 《Foundations of Physics》1997,27(12):1623-1636
The quantum Zeno effect (QZE) is often associated with the ironic maxim, “a watched pot never boils”, although the notion
of “watching” suggests a continuous activity at odds with the usual (pulsed measurement) presentation of the QZE. We show
how continuous watching can provide the same halting of decay as the usual QZE, and, for incomplete hindrance, we provide
a precise connection between the interval between projections and the response time of the continuous observer. Thus, watching
closely, but not so closely as to halt the “boiling”, is equivalent to—gives the same degree of partial hindrance as—pulsed
measurements with a particular pulsing rate. Our demonstration is accomplished by treating the apparatus for the continuous
watching as a fully quantum object. This in turn allows us a second perspective on the QZE, in which it is the modified level
structure of the combined system/apparatus Hamiltonian that slows the decay. This and other considerations favor the characterization
“dominated time evolution” for the QZE. 相似文献
14.
S. Piano J. W.A. Robinson G. Burnell M. G. Blamire 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):123-126
The physics of the π phase shift in ferromagnetic
Josephson junctions may enable a range of applications for
spin-electronic devices and quantum computing. We investigate
transitions from “0” to “π” states in Nb/Fe/Nb Josephson
junctions by varying the Fe barrier thickness from 0.5 nm to 5.5 nm. From magnetic measurements we estimate for Fe a magnetic
dead
layer of about 1.1 nm. By fitting the characteristic voltage
oscillations with existing theoretical models we extrapolate an
exchange energy of 256 meV, a Fermi velocity of 1.98 ×105
m/s and an electron mean free path of 6.2 nm, in agreement with
other reported values. From the temperature dependence of the
ICRN product we show that its decay rate exhibits a nonmonotonic
oscillatory behavior with the Fe barrier thickness. 相似文献
15.
V. N. Berzhanskiĭ A. I. Gorbovanov S. N. Polulyakh N. V. Pronina 《Physics of the Solid State》1998,40(8):1357-1359
The effect of silicon impurities on the damping of spin-echo signals from the 57Fe nuclei of tetrahedral Fe3+ ions in epitaxial yttrium-iron-garnet films was investigated. It was found that for silicon concentrations 0.015⩽x⩽0.037 the damping of the spin echo is a two-component process, which made it possible to separate nuclei into two types,
differing by both the longitudinal and transverse magnetic relaxation times. For silicon concentrations 0.044⩽x⩽0.073 the decay of the echo can be described by one exponential and all nuclei in the sample have the same transverse relaxation
times and the same longitudinal relaxation times. The experimental results are interpreted on the basis of the supposition
that impurity “macromolecules” form around the Si4+ ions. The relaxation times of the iron nuclei in a “macromolecule” are much shorter than the relaxation times of iron nuclei
belonging to the matrix ions. The radius of a “macromolecule” is estimated on the basis of percolation theory.
Fiz. Tverd. Tela (St. Petersburg) 40, 1494–1497 (August 1998) 相似文献
16.
V. ?vor?ík O. Kvítek O. Lyutakov J. Siegel Z. Kolská 《Applied Physics A: Materials Science & Processing》2011,102(3):747-751
Abstract The effects of annealing on gold structures sputtered onto glass substrate were studied using AFM, UV-Vis methods
and electrical measurements. The colour of the as-deposited films changes from blue to green with increasing deposition time.
After 1 hour annealing at 300°C the structures acquire red colour regardless of the film thickness. The annealing results
in dramatic changes of surface morphology and roughness and creation of relatively large “spherolytic and hummock-like” structures
in the gold layer. For deposited structures a non-zero optical band gap EgoptE_{\mathrm{g}}^{\mathrm{opt}} was determined from UV-Vis spectra using Tauc’s model and it indicates a semi-conducting character of the structures. The
annealing leads to an increase of the band gap. Electrical resistance of the deposited unannealed structures decreases dramatically
for deposition times above 50 s. For annealed structures the resistance fall comes until after 250 s deposition time. 相似文献
17.
《Solid State Ionics》2006,177(19-25):1875-1878
Zinc gallate (ZnGa2O4) thin film phosphors have been formed on ITO glass substrates by a chemical solution method with starting materials of zinc acetate dihydrate, gallium nitrate hydrate and 2-methoxiethanol as a solution. The thin films were firstly dried at 100 °C and fired at 500 °C for 30 min and then, annealed at 500 °C and 600 °C for 30 min under an annealing atmosphere of 3% H2/Ar. XRD patterns of the thin film phosphors showed (311) and (220) peak indicating ZnGa2O4 crystalline phase in which all the (311) peaks of the film phosphors synthesized on ITO glass and soda-lime glass revealed high intensity with increasing annealing temperature from 500 °C to 600 °C. The ZnGa2O4 thin film phosphors represented marked change in AFM surface morphologies according to an annealing temperature under an annealing atmosphere (3% H2/Ar). The film phosphor, annealed at 600 °C, showed the embossed pattern with relatively regular spacing in AFM surface morphology. The ZnGa2O4 thin film phosphors formed on ITO glass, which were annealed at different temperatures and showed distinctive spectra with peak wavelengths of 434 nm and 436 nm in the blue emission region. 相似文献
18.
I. P. Suzdalev Yu. V. Maksimov V. N. Buravtsev V. K. Imshennik S. V. Novichihin V. V. Matveev I. S. Lyubutin 《Russian Journal of Physical Chemistry B, Focus on Physics》2012,6(1):163-168
The monodisperse magnetite nanoclusters 13–15 nm in size were synthesized and studied. The nanoclusters were stabilized in
colloid solution by means of surface-active-substance (SAS)—oleic acid in the presence, paraffin—docosane and separated from
each other by paraffin layers at the distance approximately ∼3 nm. The first order magnetic phase transition was observed
in magnetite, when magnetization of a cluster disappears by jump at some critical temperature similar to that of the Curie
or Neel temperatures typical of the bulk material. The observed effect is explained by the influence of surface-induced defects
in the nanomagnetite. The developed surface of a cluster generates defects and causes surface tension. The model is proposed,
and transition from a paramagnetic to magnetic ordered (superparamagnetic) state of a cluster is found experimentally by applying
an external magnetic field which is more than some critical one. Nanomagnetite itself exists in a special “oxidized condition”,
which elementary cell is the same as in normal magnetite, but it contains only trivalent cations in a B-sublattice. 相似文献
19.
Marco Castriota Nathalie Epervrier Tiziana Barone Giuseppe De Santo Enzo Cazzanelli 《Ionics》2007,13(4):205-211
In this work, the mechanism of the “gelation” process and the thermal-induced structural modifications of thin film of vanadium
pentoxide xerogels deposited on indium tin oxide (ITO)-coated glasses have been studied. Vanadium pentoxide xerogel has been
prepared by using the sol–gel proton exchange resin route without any resin pretreatment. To monitor the effect of the “resin
efficiency” on the gelation process, the solution coming out from the resin has been collected in a sequence of different
containers (vials), separately investigated by Raman spectroscopy. After the spin coating deposition, the thin films of vanadium
pentoxide gel have been subjected to different annealing treatments. The highest thermal treatment (600 °C) induces a complete
transformation of the gel phase into an anhydrous polycrystalline phase of a sodium-containing vanadate, different from the
usual V2O5 crystal. It is due to the diffusion of foreign ions (mainly sodium) coming from the substrate into the vanadium oxide layer. 相似文献
20.
4 F3/2 level of Nd3+ in aluminosilicate optical fiber preforms after 807-nm excitation are reported in the temperature range from 15 °C to 500 °C
for Nd2O3 concentrations in the range from 0.2 to [%wt]0.9 and Al2O3 concentrations of between [%wt]3.8 and [%wt]8. At room temperature it is observed that for concentrations of less than [%wt]0.6
Nd2O3 the fluorescence decay is approximately exponential; for the higher Nd2O3 concentrations the decay is increasingly bi-exponential. We have identified a “slow” (≈500 μs) and a “fast” (≈100 μs) decay
time; the slow decay is attributed to isolated ions and the faster decay to energy transfer between homogeneously dispersed
ions. The measured 1/e folding fluorescence decay time τ decreases slowly at a constant rate of -0.08±0.007 μs/K for [%wt]0.9
Nd2O3. It is shown that increasing the Al2O3 concentration tends to suppress this temperature quenching effect. A radiative decay time of 640 μs is obtained by Judd–Ofelt
analysis.
Received: 24 October 1997/Revised version: 2 February 1998 相似文献