Solid State Phenomena Vols. 121-123

Abstract: It is shown that negative electric permittivity ε and magnetic permeability μ recently discovered in a photonic crystal in the vicinity of the Γ-point are properties of propagating modes only. The evanescent modes rather decay than increase in the bulk of the crystal though they may be amplified by surface waves. If surface support such waves, the evanescent waves may improve the image of a thin Veselago lens. It is shown that a “perfect lens” contradicts to the wave optics and a criterion of “superlensing” is formulated.

Abstract: The size-dependent valence-conduction bandgap of semiconductor nanocrystals are predicted based on a model for size-dependent cohesive energy, without any adjustable parameter. The model predicts an increase of the bandgap of semiconductors with decreasing crystalline sizes. It is found that the model predictions are in good agreement with the available experimental results for Si, ZnS, ZnSe, CdS, and CdSe nanocrystals.

Abstract: Performing an event-based continuous kinetic Monte Carlo (KMC) simulation, We investigate the growth conditions which are important to form semiconductor quantum dot (QD) in molecular beam epitaxy (MBE) system. The simulation results provide a detailed characterization of the atomic kinetic effects. The KMC simulation is also used to explore the effects of periodic strain to the epitaxy growth of QD. The simulation results are in well qualitative agreement with experiments.

Abstract: The eigenvalue problem in a non-concentric circular quantum corral was studied with a conformal mapping method. The energy spectra of electrons show the properties of anti-crossing between the nearby energy levels. This property of energy spectra is caused by the Jacobian of the conformal transformation. We also give the probability density of the electronic states that confined in the non-concentric circular quantum corral. Quantum corral geometry has a stronger effect on electronic states of higher energies than that of lower energies.

Abstract: Based on Monte Carlo simulation we study the coercivity of iron nanowire deposited in chemically widened anodic aluminum oxide films. The coercivity is found to depend on the diameter and aspect ratio of the nanowire, and it decreases with increasing nanowire diameter, which is consistent with the experimental result. Two kinds of discretization cells regular global-shaped and regular cubic-shaped are used as minimum element. The simulation result reveals that the regular global-shaped discretization cell allows for more accurate calculated result while comparing to the experimental result than the cubic-shaped discretization cell does. The simulated coercivity as a function of temperature with different diameters shows that the data can be described well by the T-c power-law, and the diameter dependence of the exponent c displays a maximum peak.

Abstract: In this paper, we simulate the magnetization dynamic processes of the multilayer films, and calculate their hysteresis loop areas using Monte Carlo method. The simulated results indicate that, the size and anisotropy strength of the anisotropy multilayer films influence evidently the dynamic phase transition, and the phase transition temperature increases with enhancing values of the anisotropy constant and layer thickness. It is also found that, with increasing number of layers of films, the value of α decreases, while the magnitudes of β and γ increase. On the contrary, with increasing anisotropy strength, the value of α increases, while the magnitudes of β and γ reduce.

Abstract: Theoretical analysis of the ionized fluid flowing through a cone-shaped nanopore is presented. The internal cross section of the cone-shaped channel is in the range from micro- to nanometer and gradual change from larger to smaller than the Debye length for the ions. The model is developed to predict the ionized fluid flow behaviors in cone-shaped micro/nanochannels. The velocity profiles of ion flow that occur in nanopores are obtained.

Abstract: In this paper, the effects of Na+ concentration on the overstretching transition of B-DNA molecule at physiological temperature are studied by both experimental and numerical methods. Using optical tweezers, the relationship of external force and relative extension is obtained by stretching single B-DNA molecule at 37°C. As the concentration increases from 0.909mM to 909mM, the overstretching transition force increases from 65.65 ± 1.2pN to 43.07 ± 1.2pN. An analytical expression is derived, which shows that overstretching transition force is linear with the natural logarithm of salt concentration. Based on a previous model, a three-dimensional model is proposed herein and solved by Metropolis Monte Carlo method. The bending deformation of DNA backbones, cooperativity of base-stacking interactions, electrostatic interactions, and spatial effects of DNA double helix structure are taken into account. Our key contribution is that the electrostatic energy is explicitly given as a function of folding angle and Na+ concentration. A new parameter is also introduced to account for the cooperativity of base-stacking interactions. The numerical results of this model are in good agreement with our experimental results.

Abstract: We have calculated angular and energy loss distributions of electrons transmitted through masks for electron projection lithography by using a Monte Carlo simulation method. The angular and energy loss distributions are much wider in the mask stack than those in the membrane layer. The large non-scattering and non-energy-loss probabilities are also found for the membrane layer. High contrast image can thus be achieved within a small size of aperture.

Abstract: Several fundamental problems in hydrophobic force measurements by using AFM are discussed in this paper. A novel method for colloid probe preparation based on the chemical etching technology is proposed, which is specially fit for the unique demands of the hydrophobic force measurements by AFM. The features of three different approaches for the determination of spring constants of the rectangular cantilevers, including geometric dimension, Cleveland and Sader methods are compared. The influences of the sizes of the colloids on the measurements of the hydrophobic force curves are investigated. Our experimental results showed that, by selecting a colloid probe with a proper spring constant and a tip size, a real hydrophobic force, even the complete hydrophobic interaction force curve with every subtle change in details might be measured by using AFM.