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1.
实验发现动态电压应力条件下,由于栅氧化层很薄,高电平应力时间内隧穿入氧化层的电子与陷落在氧化层中的空穴复合产生中性电子陷阱,中性电子陷阱辅助电子隧穿.由于每个周期的高电平时间较短(远远低于电荷的复合时间),隧穿到氧化层的电子很少,同时低电平应力时间内一部分电荷退陷,形成的中性电子陷阱更少.随着应力时间的累积,中性电子陷阱达到某个临界值,栅氧化层突然击穿.高电平时形成的陷阱较少和低电平时一部分电荷退陷,使得器件的寿命提高.
关键词:
超薄栅氧化层
斜坡电压
经时击穿 相似文献
2.
Living polymers are formed by reversible association of primary units (unimers). Generally the chain statistical weight involves
a factor σ < 1 suppressing short chains in comparison with free unimers. Living polymerization is a sharp thermodynamic transition
for σ ≪ 1 which is typically the case. We show that this sharpness has an important effect on the kinetics of living polymerization
(one-dimensional association). The kinetic model involves i) the unimer activation step (a transition to an assembly-competent
state); ii) the scission/recombination processes providing growth of polymer chains and relaxation of their length distribution.
Analyzing the polymerization with no chains but unimers at t = 0 , with initial concentration of unimers M ≳ M
* (M* is the critical polymerization concentration), we determine the time evolution of the chain length distribution and find
that: 1) for M
* ≪ M ≪ M
*/σ the kinetics is characterized by 5 distinct time stages demarcated by 4 characteristic times t1, t2, t3 and t*; 2) there are transient regimes (t
1 ≲ t ≲ t
3) when the molecular-weight distribution is strongly non-exponential; 3) the chain scissions are negligible at times shorter
than t2. The chain growth is auto-accelerated for t
1 ≲ t ≲ t
2 : the cut-off chain length (= polymerization degree 〈n〉w
N
1 ∝ t
2 in this regime. 4) For t
2 < t < t
3 the length distribution is characterized by essentially 2 non-linear modes; the shorter cut-off length N1 is decreasing with time in this regime, while the length scale N2 of the second mode is increasing. (5) The terminal relaxation time of the polymer length distribution, t*, shows a sharp maximum in the vicinity of M*; the effective exponent
is as high as ∼ σ-1/3 just above M*. 相似文献
3.
V. Fourmaux-Demange A. Brûlet F. Boué P. Davidson P. Keller J.P. Cotton 《The European physical journal. E, Soft matter》2000,1(4):301-317
We have studied the rheology and the conformation of stretched comb-like liquid-crystalline polymers. Both the influence of
the comb-like structure and the specific effect of the nematic interaction on the dynamics are investigated. For this purpose,
two isomers of a comb-like polymetacrylate polymer, of well-defined molecular weights, were synthesized: one displays a nematic
phase over a wide range of temperature, the other one has only an isotropic phase. Even with high degrees of polymerization
N, between 40 and 1000, the polymer chains studied were not entangled. The stress-strain curves during the stretching and relaxation
processes show differences between the isotropic and nematic comb-like polymers. They suggest that, in the nematic phase,
the chain dynamics is more cooperative than for a usual linear polymer. Small-angle neutron scattering has been used in order
to determine the evolution of the chain conformation after stretching, as a function of the duration of relaxation t
r. The conformation can be described with two parameters only: , the global deformation of the polymer chain, and p, the number of statistical units of locally relaxed sub-chains. For the comb-like polymer, the chain deformation is pseudo-affine:
is always smaller than (the deformation ratio of the whole sample). In the isotropic phase, has a constant value, while pincreases as tr. This latter behavior is not that expected for non-entangled chains, in which p varies as t
r
1/2 (Rouse model). In the nematic phase, decreases as a stretched exponential function of t
r, while p remains constant. The dynamics of the comb-like polymers is discussed in terms of living clusters from which junctions are
produced by interactions between side chains. The nematic interaction increases the lifetime of these junctions and, strikingly,
the relaxation is the same at all scales of the whole polymer chain.
Received 5 May 1999 and Received in final form 18 October 1999 相似文献
4.
Abstract Trapped electrons (et ?) were detected in irradiated PVA films at 77°K. Yield of et ? was decreased as evaporating water from the films, indicating that water molecules contribute to construct pre-existing traps in the polymer. The radical produced at 77°K was identified as a precursor of the radical produced at room temperature. 相似文献
5.
采用非格点珠簧球链模型, 结合Monte Carlo方法, 研究了半刚性高分子链受限于无限长圆柱体的构象性质. 模拟结果表明: 在圆柱体内表面附近具有吸附能的情况下, 当弯曲能b由小到大变化时, 发现半刚性高分子链由开始时的无规则被吸附在圆柱体内表面, 到逐渐出现螺旋结构, 最后伸展成类似棒状的结构. 同时计算了不同弯曲能b时的半刚性高分子链的平均螺旋数Nt, 平均每条链单体的螺旋百分比Ph和能量涨落. 发现高分子链螺旋结构的形成与转变, 不仅与圆柱体半径R的大小有关, 还与弯曲能b的大小有关. 研究结果能有助于加深对受限生物大分子构象的认识. 相似文献
6.
B. O'Shaughnessy D. Vavylonis 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):363-372
We study the reaction kinetics of end-functionalized polymer chains dispersed in an unreactive polymer melt. Starting from
an infinite hierarchy of coupled equations for many-chain correlation functions, a closed equation is derived for the 2nd
order rate constant k after postulating simple physical bounds. Our results generalize previous 2-chain treatments (valid in dilute reactants limit)
by Doi [#!doi:inter2!#], de Gennes [#!gennes:polreactionsiandii!#], and Friedman and O'Shaughnessy [#!ben:interdil_all_aip!#],
to arbitrary initial reactive group density n0 and local chemical reactivity Q. Simple mean field (MF) kinetics apply at short times, .For high Q, a transition occurs to diffusion-controlled (DC) kinetics with (where xt is rms monomer displacement in time t) leading to a density decay . If n0 exceeds the chain overlap threshold, this behavior is followed by a regime where during which k has the same power law dependence in time, , but possibly different numerical coefficient. For unentangled melts this gives while for entangled cases one or more of the successive regimes ,t
-3/8
and t
-3/4
may be realized depending on the magnitudes of Q and n0. Kinetics at times longer than the longest polymer relaxation time are always MF. If a DC regime has developed before then the long time rate constant is where R is the coil radius. We propose measuring the above kinetics in a model experiment where radical end groups are generated
by photolysis.
Received: 2 June 1998 / Revised: 9 July 1998 / Accepted: 10 July 1998 相似文献
7.
8.
《Composite Interfaces》2013,20(1):83-92
A photon transmission method was used to study latex film formation induced by organic solvent vapor. Various films with the same latex content were prepared separately from the poly(methyl methacrylate) (PMMA) particles and exposed to vapor of chloroform-heptane mixture in various percentage volumes of chloroform. Transmitted photon intensities, I tr, from these films increased in time under vapor exposure. The increase in I tr is attributed to the increase in 'crossing density' at the junction surface. The Prager-Tirrell model was employed to obtained back-and-forth frequency, ν of the reptating polymer chain during film formation induced by solvent vapor. ν values were obtained and found to be strongly correlated with the percent of chloroform in the solvent mixture. At high and low chloroform contents, polymer chains diffuse according to t 1/2 and t 1/4 laws respectively. 相似文献
9.
10.
We develop a renormalization group approach for cyclizing polymers for the case when chain ends are initially close together
(ring initial conditions). We analyze the behavior at times much shorter than the longest polymer relaxation time. In agreement
with our previous work (Europhys. Lett.
73, 621 (2006)) we find that the leading time dependence of the reaction rate k(t) for ring initial conditions and equilibrium initial conditions are related, namely k
ring(t) ∝ t
-δ and k
eq(t) ∝ t
1-δ for times less than the longest polymer relaxation time. Here δ is an effective exponent which approaches δ = 5/4 for very
long Rouse chains. Our present analysis also suggests a “sub-leading” term proportional to (ln t)/t which should be particularly significant for smaller values of the renormalized reaction rate and early times. For Zimm dynamics,
our RG analysis indicates that the leading time dependence for the reaction rate is k(t) ∼ 1/t for very long chains. The leading term is again consistent with the expected relation between ring and equilibrium initial
conditions. We also find a logarithmic correction term which we “exponentiate” to a logarithmic form with a Landau pole. The
presence of the logarithm is particularly important for smaller chains and, in the Zimm case, large values of the reaction
rate. 相似文献
11.
Kurt Schroeder 《Zeitschrift für Physik B Condensed Matter》1976,25(1):91-95
We present a phenomenological model describing the trapping and release of mobile defects at random inhomogeneities. The traps are characterized by two parameters, the capture radiusR
t, describing the range of the interaction and the binding energyE
b describing the escape. We give an integral representation of the correlation function of the mobile particles in the presence of traps. For large distances the correlation function can be described by a simple diffusional process with an effective diffusion constant. Finally we discuss the neutron scattering by mobile defects resulting from this trapping model. 相似文献
12.
We investigate, using numerical simulations and analytical arguments, a simple one-dimensional model for the swelling or the
collapse of a closed polymer chain of size N, representing the dynamical evolution of a polymer in a Θ-solvent that is rapidly changed into a good solvent (swelling)
or a bad solvent (collapse). In the case of swelling, the density profile for intermediate times is parabolic and expands
in space as t
1/3, as predicted by a Flory-like continuum theory. The dynamics slows down after a time ∝N
2 when the chain becomes stretched, and the polymer gets stuck in metastable “zig-zag” configurations, from which it escapes
through thermal activation. The size of the polymer in the final stages is found to grow as . In the case of collapse, the chain very quickly (after a time of order unity) breaks up into clusters of monomers (“pearls”).
The evolution of the chain then proceeds through a slow growth of the size of these metastable clusters, again evolving as
the logarithm of time. We enumerate the total number of metastable states as a function of the extension of the chain, and
deduce from this computation that the radius of the chain should decrease as 1/ln(ln t). We compute the total number of metastable states with a given value of the energy, and find that the complexity is non-zero
for arbitrary low energies. We also obtain the distribution of cluster sizes, that we compare to simple “cut-in-two” coalescence
models. Finally, we determine the aging properties of the dynamical structure. The subaging behaviour that we find is attributed
to the tail of the distribution at small cluster sizes, corresponding to anomalously “fast” clusters (as compared to the average).
We argue that this mechanism for subaging might hold in other slowly coarsening systems.
Received 23 October 2000 相似文献
13.
An exact solution is obtained for the survival fraction in the one-dimensional diffusion problem with randomly distributed deep traps. The time decay is studied both with and without a bias field. The small concentration (x) long time (t) decay behaves as exp[-(x
2
t/t
0)1/3]. The exact results are compared with the coherent potential approximation (CPA) and the first passage time approach (FPT). We find that in most cases of practical interest the FPT is superior to the CPA. 相似文献
14.
Jin Min Kim 《Physica A》1999,270(3-4)
Finite-temperature-directed polymer in random potentials is described by a transfer matrix method. On 4+1 dimensions, the evidence for a finite-temperature phase transition is found at Tc≈0.18, where the free energy fluctuation grows logarithmically as a function of time t. When TTc, the fluctuation of the free energy grows as tω with ω≈0.156. The phase transition of the restricted solid-on-solid model, which is closely related to the directed polymer problem through the Kardar–Parisi–Zhang equation, is also discussed. 相似文献
15.
The blinking of quantum dots under the action of laser radiation is described based on a model of a binary (two-state) renewal
process with on (fluorescent) and off (non fluorescent) states. The T
on and T
off sojourn times in the on and off states are random and power-law distributed with exponents 0 < α < 1 and 0 < β < 1; the averages
of the on and off times are infinite. As a consequence of this, the Gaussian statistics is inapplicable and the process is
described using a more general statistics. An equation for the density of distribution p(t
on|t) of the total on time during the observation time t is derived that contains derivatives of fractional orders α and β. A solution to this equation is found in terms of fractional
stable distributions. The Poisson transform of the density p(t
on|t) leads to the photon counting distribution and determines the fluorescence statistics. It is demonstrated that, if a blinking
process with exponents α < β is implemented, then, at fairly long times, the on time will considerably prevail over the off
time, i.e., blinking will be suppressed. This behavior is evidenced by the types of distributions of the total fluorescence
time, the decay of relative fluctuations, and the Monte Carlo simulated trajectories of the process. 相似文献
16.
C. Ortiz E. Mena M. Sabido J. Socorro 《International Journal of Theoretical Physics》2008,47(5):1240-1251
Using the WKB-like and Hamilton procedures classical solutions to commutative and noncommutative cosmology are found. This
is carried out in the Bianchi type I cosmological model coupled to barotropic perfect fluid and cosmological constant. Noncommutativity
is achieved by modifying the symplectic structure considering that minisuperspace variables do not commute, using a deformation
between all the minisuperspace variables. It is shown that the anisotropic parameter β
±nc
for some value in the Λ cosmological term and noncommutative θ parameter, present a dynamical isotropization until a critical cosmic time t
c
. After this time the effects of minisuperspace noncommutativity in the isotropization seem to disappear. 相似文献
17.
《Journal of Macromolecular Science: Physics》2013,52(3-4):847-865
Direct evidence that nuclei are formed during the induction period of crystallization is obtained for the first time by means of small-angle X-ray scattering (SAXS). Polyethylene (PE) was used as a model crystalline polymer. The nucleating agent was mixed with PE in order to increase the scattering intensity I x from nuclei as large as 104 times bigger than usual. I x increased soon after quenching to the crystallization temperature from the melt and saturated after some time. A new theory is proposed to estimate the size of the nuclei N, the number density distribution of nuclei with N at time t, f(t,N), and the induction time τ i, by analyzing the SAXS scattering intensity. The volume-averaged size of the nuclei was nearly the same as that of critical nuclei and does not change so much with time during the induction period. Lamellae start stacking much later than nuclei start forming. 相似文献
18.
The decay dynamics of a local excitation interacting with a non-Markovian environment, modeled by a semi-infinite tight-binding chain, is exactly evaluated. We identify distinctive regimes for the dynamics. Sequentially: (i) early quadratic decay of the initial-state survival probability, up to a spreading time tS, (ii) exponential decay described by a self-consistent Fermi Golden Rule, and (iii) asymptotic behavior governed by quantum diffusion through the return processes, leading to an inverse power law decay. At this last cross-over time tR a survival collapse becomes possible. This could reduce the survival probability by several orders of magnitude. The cross-over times tS and tR allow to assess the range of applicability of the Fermi Golden Rule and give the conditions for the observation of the Zeno and anti-Zeno effect. 相似文献
19.
S. De Toro Arias X. Waintal J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):149-158
The interplay between the quantum interferences responsible for one particle localization over a length L1, and the partial dephasing induced by a local interaction of strength U with another particle leading to partial delocalization over a length L
2
> L
1
, is illustrated by a study of the motion of two particles put close to each other at the initial time. Localization is reached
in two steps. First, before the time t1 necessary to propagate over L1, the interaction slows down the ballistic motion. On the contrary, after t1 the interaction favors a very slow delocalization, characterized by a spreading of the center of mass, until L2 is reached. This slow motion is related to the absence of quantum chaos in this one dimensional model, the interaction being
only able to induce weaker chaos with critical spectral statistics. Under appropriate initial conditions, the motion remains
invariant under the duality transformation mapping the behavior at small U onto the behavior at large U.
Received 24 August 1998 相似文献
20.
P. Hoyningen-Huene 《Physica A》1975,83(3):584-594
We present calculations of the coarse-grained entropy Scg(t) for the model of a classical point particle enclosed in a two-dimensional box with perfectly reflecting walls. We find in comparison with the one-dimensional case that the fluctuations of Scg(t) and of the expectation values of the position have decreased, and that Scg(t) does not take its asymptotic value at regular time intervals. The times after which Scg(t) and the expectation values have approximately reached their equilibrium values, are about equal; recurrence times are rather clearly separated from this time. Finally, we give a general estimate on the change of an expectation value due to a refinement of the cells. 相似文献