Convergence of Phase-Field Free Energy and Boundary Force for Molecular Solvation

We study a phase-field variational model for the solvaiton of charged molecules with an implicit solvent. The solvation free-energy functional of all phase fields consists of the surface energy, solute excluded volume and solute-solvent van der Waals dispersion energy, and electrostatic free energy. The surface energy is defined by the van der Waals--Cahn--Hilliard functional with squared gradient and a double-well potential. The electrostatic part of free energy is defined through the electrostatic potential governed by the Poisson--Boltzmann equation in which the dielectric coefficient is defined through the underlying phase field. We prove the continuity of the electrostatics---its potential, free energy, and dielectric boundary force---with respect to the perturbation of dielectric boundary. We also prove the $\Gamma$-convergence of the phase-field free-energy functionals to their sharp-interface limit, and the equivalence of the convergence of total free energies to that of all individual parts of free energy. We finally prove the convergence of phase-field forces to their sharp-interface limit. Such forces are defined as the negative first variations of the free-energy functional; and arise from stress tensors. In particular, we obtain the force convergence for the van der Waals--Cahn--Hilliard functionals with minimal assumptions.Comment: 40 page

Review of damage problems of the soft substrate interlayer film

This paper reviews the research progress of soft substrate interlayer film, including the applications and the preparation methods of the soft substrate interlayer film, the testing means of the films’ structure and composition and the researches of the film damage, especially the dynamic damage. As well as the future research directions and applications are put forward

Experimental and numerical investigation of bulging behaviour of hyperelastic textured tubes

The inflation and propagation of a localized instability in elastic tubes shares the same mathematical features with a range of other localization problems, including buckling propagation in long metal tubes under external pressure. Recent research into origami-inspired tubular geometries has suggested that geometric texturing is able to significantly improve metal pipe resistance to propagation buckling failures, with an increase in critical and propagation pressures. This paper aims to investigate whether texturing generates a similar improvement in hyperelastic tubes under axial loading and internal pressure, with elastomer origami structures of recent interest for use as soft actuators and robots. A new fabrication method with 3D printed moulds in a dip process was first developed to enable fabrication of textured tube samples. An experimental study was then conducted on inflated smooth and textured latex tubes, with instability formation observed at a 1 ms resolution. Comparative numerical models with a Mooney–Rivlin material were able to provide a good prediction of experimentally-observed behaviours up to and slightly past the critical pressure and bulge formation. A parametric numerical study is then conducted to show that the number of divisions in the axial direction and circumferential direction have no and modest effects on critical pressure, respectively. The experimental and numerical investigations both showed that the critical pressure of the textured tube was increased compared to the smooth tube, however the degree of increase was a modest 8% and so unlikely to be of significant practical benefit. This work can provide reference and guidelines for future investigations of tubular inflatable origami structures

Atomic Layer Deposition of High Quality HfO\u3csub\u3e2\u3c/sub\u3e Using In-Situ Formed Hydrophilic Oxide as an Interfacial Layer

High-quality HfO2 cannot be grown directly on Si substrate using atomic layer deposition (ALD), and an interfacial oxide layer is needed. Traditionally, interfacial oxide layer is formed either in SC1 solution (2 NH4OH: 4 H2O2: 200 H2O) or by ozonated water spraying. A highly hydrophilic SiO2 interfacial layer was in-situ formed in the ALD chamber using 1 cycle of ozone and water. The HfO2 deposited on this interfacial layer showed great growth linearity. The gate leakage current is comparable to that formed using chemical oxide as the interfacial layer. The capacitance-voltage (C-V) curves have negligible frequency dispersion and hysteresis, which suggest high quality in both the interface and electrical properties. The in-situ formation of hydrophilic interfacial layer have advantages over the traditional interfacial layer. This might be useful for formation of interfacial layer on sophisticated 3-D MOS structures such as FinFETs and nanowire FETs. In addition, the chemical oxidation step can be eliminated from the integrated circuits manufacturing processes, which is economically beneficial to the industry

Nanoscale Footprints of Self-Running Gallium Droplets on GaAs Surface

In this work, the nanoscale footprints of self-driven liquid gallium droplet movement on a GaAs (001) surface will be presented and analyzed. The nanoscale footprints of a primary droplet trail and ordered secondary droplets along primary droplet trails are observed on the GaAs surface. A well ordered nanoterrace from the trail is left behind by a running droplet. In addition, collision events between two running droplets are investigated. The exposed fresh surface after a collision demonstrates a superior evaporation property. Based on the observation of droplet evolution at different stages as well as nanoscale footprints, a schematic diagram of droplet evolution is outlined in an attempt to understand the phenomenon of stick-slip droplet motion on the GaAs surface. The present study adds another piece of work to obtain the physical picture of a stick-slip self-driven mechanism in nanoscale, bridging nano and micro systems

Origins of 1/f noise in nanostructure inclusion polymorphous silicon films

In this article, we report that the origins of 1/f noise in pm-Si:H film resistors are inhomogeneity and defective structure. The results obtained are consistent with Hooge's formula, where the noise parameter, αH, is independent of doping ratio. The 1/f noise power spectral density and noise parameter αH are proportional to the squared value of temperature coefficient of resistance (TCR). The resistivity and TCR of pm-Si:H film resistor were obtained through linear current-voltage measurement. The 1/f noise, measured by a custom-built noise spectroscopy system, shows that the power spectral density is a function of both doping ratio and temperature