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21.
G. Michałek B.R. Bułka 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):121-128
The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of
sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized,
which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions
of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance.
An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions
to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise)
are responsible for a strong enhancement of the current noise.
Received 9 October 2001 / Received in final form 8 March 2002 Published online 9 July 2002 相似文献
22.
Experiments employing photoreflectance spectroscopy have uncovered band bending due to electrically active defects at the Si(1 1 1)–SiO2 interface after sub-keV Ar+ ion bombardment. The band bending of about 0.5 eV resembles that for Si(1 0 0)–SiO2, and both interfaces exhibit two kinetic regimes for the evolution of band bending upon annealing due to defects healing. The healing takes place about an order of magnitude more quickly at the (1 1 1) interface, however, probably because of less fully saturated bonding and higher compressive stress. 相似文献
23.
H. Kuramochi J. Okabayashi F. Takano M. Mizuguchi T. Manago H. Akinaga 《Surface science》2004,550(1-3):192-198
Strong magnetic poles at characteristic rectangular defects have been observed using a magnetic force microscope on a MnAs(
1 0 0) thin film with the thickness of 30 nm. The MnAs thin film was epitaxially grown on a GaAs(0 0 1) substrate. The magnetic poles were in one-arranging direction, being independent of the magnetization direction of the film. The poles were pinned at the edges of the rectangular defects until just below the Curie temperature, and formed a stable magnetic-field loop on the MnAs surface. The stability of the magnetic pole pinning shows the distinctive feature of the magnetic domain structure on the surface with a strong anisotropy, which was built in the heterostructure of MnAs and GaAs. 相似文献
24.
25.
Michelle J. S. Spencer Andrew Hung Ian K. Snook Irene Yarovsky 《Surface science》2003,540(2-3):420-430
The adsorption of atomic S on the Fe(1 1 0) surface is examined using density functional theory (DFT). Three different adsorption sites are considered, including the atop, hollow and bridge sites and the S is adsorbed at a quarter monolayer coverage in a p(2 × 2) arrangement. The hollow site is found to be the most stable, followed by the bridge and atop sites. At all three sites, S adsorption results in relatively minor surface reconstruction, with the most significant being that for the hollow site, with lateral displacements of 0.09 Å. Comparisons between S-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the S. At the hollow site, the presence of S causes an increase in the surface Fe d-orbital density of states between 4 and 5 eV. However, S adsorption has no significant effect on the structure and magnetic properties of the lower substrate layers. 相似文献
26.
Young C. Kim Mikhail A. Anisimov Jan V. Sengers Erik Luijten 《Journal of statistical physics》2003,110(3-6):591-609
The character of critical behavior in physical systems depends on the range of interactions. In the limit of infinite range of the interactions, systems will exhibit mean-field critical behavior, i.e., critical behavior not affected by fluctuations of the order parameter. If the interaction range is finite, the critical behavior asymptotically close to the critical point is determined by fluctuations and the actual critical behavior depends on the particular universality class. A variety of systems, including fluids and anisotropic ferromagnets, belongs to the three-dimensional Ising universality class. Recent numerical studies of Ising models with different interaction ranges have revealed a spectacular crossover between the asymptotic fluctuation-induced critical behavior and mean-field-type critical behavior. In this work, we compare these numerical results with a crossover Landau model based on renormalization-group matching. For this purpose we consider an application of the crossover Landau model to the three-dimensional Ising model without fitting to any adjustable parameters. The crossover behavior of the critical susceptibility and of the order parameter is analyzed over a broad range (ten orders) of the scaled distance to the critical temperature. The dependence of the coupling constant on the interaction range, governing the crossover critical behavior, is discussed. 相似文献
27.
Image potential resonances on the Sn/Ge(1 1 1) α-phase are investigated by two closely related methods: specular electron reflection and so-called selective electron scattering. Electrons from image resonances are detected on this surface at 120 and 300 K, i.e. below and above the phase transition at about 200 K. The dispersion of the image resonances reveals at these two temperatures equivalent effective electron masses, which are characteristic for this type of electronic surface states. The results of the two methods are consistent according to the similarity of the scattering processes. Changes in the loss peak intensity with the annealing temperature are assigned to the surface quality and are reflected by characteristic photoemission intensities. 相似文献
28.
Kazuhiro Kurata Masataka Shibata Shigeru Sakamoto 《Applied Mathematics and Optimization》2004,50(3):259-278
Let $\Omega$ be a bounded domain in ${\bf R^n}$ with Lipschitz
boundary,
$\lambda >0,$ and $1\le p \le (n+2)/(n-2)$ if $n\ge 3$ and $1\le p< +\infty$
if $n=1,2$. Let $D$ be a measurable subset of $\Omega$ which belongs
to the class
$
{\cal C}_{\beta}=\{D\subset \Omega \quad | \quad |D|=\beta\}
$
for the prescribed $\beta\in (0, |\Omega|).$
For any $D\in{\cal C}_{\beta}$, it is well known that
there exists a unique
global minimizer $u\in H^1_0(\Omega)$, which we denote by
$u_D$, of the functional
\[\quad
J_{\Omega,D}(v)=\frac12\int_{\Omega}|\nabla v|^2\,
dx+\frac{\lambda}{p+1}\int_{\Omega}|v|^{p+1}\, dx
-\int_{\Omega}\chi_Dv\,dx
\]
on $H^1_0(\Omega)$.
We consider the optimization problem
$
E_{\beta,\Omega}=\inf_{D\in {\cal C}_{\beta}} J_D(u_D)
$
and say that
a subset $D^*\in {\cal C}_{\beta}$ which attains
$E_{\beta,\Omega}$
is an optimal configuration to this problem.
In this paper we show the existence, uniqueness
and non-uniqueness, and
symmetry-preserving and symmetry-breaking phenomena of the
optimal configuration $D^*$ to this
optimization problem in various settings. 相似文献
29.
Summary A new, rapid and simple method is described and applied to resolve and quantify mixtures of prednisolone, Zn-bacitracin and phenylephrine. The determination was accomplished by MEKC. The separation was carried out at 25 °C and 30 kV, using a 5 mM phosphate-5 mM borate buffer (pH=8.2), 40 mM SDS as background electrolyte. Under these conditions, the run time was 6.6 min and the limits of quantification were about 1.0 mg L–1 for every component. Repeatability and reproducibility studies were achieved showing no significant differences at 95% confidence level. The MEKC method has been applied for quantifying these compounds in different commercials pharmaceuticals products, without separations steps. 相似文献
30.
A.A. Dakhel 《Journal of Physics and Chemistry of Solids》2004,65(11):1765-1771
Thin Eu-In solid solution oxide films (SS) were grown on Si (P) substrates to form MOS devices. The samples were characterised by X-ray fluorescence and X-ray diffraction techniques. The ac-conductance and capacitance of the devices were studied as a function of frequency in the range 500 Hz to 100 kHz, temperature in the range 293-400 K and gate voltage. The investigation established that: (1) the prepared SS exhibit a sudden reversible structural change at about 370 K, (2) the frequency dependence for f>10 kHz of the ac-conductivity and capacitance of the insulator at room temperature is controlled by the ‘corrected barrier hopping’ CBH model, (3) the temperature dependence of the ac-conductance which shows a small activation energy characterises the hopping process of current carriers between equilibrium sites, and (4) the prepared transparent SS have a sufficiently high relative permittivity ?, around 30, which suggests they are promising candidates for high-? dielectric applications. 相似文献