Electric field-dependent charge transport in organic semiconductors

An analytical description is elaborated for the variable range hopping conduction mechanism in the presence of temperature and electric fields for quasi-three-dimensional organic semiconductor systems. In the proposed description, it is assumed that the localized states are randomly distributed in energy and space coordinates. The expression for the hopping conductivity is obtained for the Gaussian density of states. The model is applied to the analysis of both temperature and electric field-dependent hopping transport in organic semiconductors. It is shown that the Poole–Frenkel behavior is only valid in medium electric field regime. Moreover, we conclude that the electric field determines whether the temperature dependence of conductivity in organic semiconductors obeys the Arrhenius law.

Phase oscillators with global sinusoidal coupling evolve by Mobius group action

Systems of N identical phase oscillators with global sinusoidal coupling areknown to display low-dimensional dynamics. Although this phenomenon was firstobserved about 20 years ago, its underlying cause has remained a puzzle. Herewe expose the structure working behind the scenes of these systems, by provingthat the governing equations are generated by the action of the Mobius group, athree-parameter subgroup of fractional linear transformations that map the unitdisc to itself. When there are no auxiliary state variables, the group actionpartitions the N-dimensional state space into three-dimensional invariantmanifolds (the group orbits). The N-3 constants of motion associated with thisfoliation are the N-3 functionally independent cross ratios of the oscillatorphases. No further reduction is possible, in general; numerical experiments onmodels of Josephson junction arrays suggest that the invariant manifolds oftencontain three-dimensional regions of neutrally stable chaos.

The internal energy of CO2 produced by the catalytic oxidation of CH3OH by O2 on polycrystalline platinum

Design and optimization of a double-enzyme glucose assay in microfluidic lab-on-a-chip

Spectroscopic Ellipsometry Characterization of High-k films on SiO[sub 2]∕Si

Characterization of HfO[sub 2] and Hafnium Silicate Films on SiO[sub 2]∕Si

High-Resolution Rutherford Backscattering Analysis of Nanoscale Thin Films

Near coalescent submicron polycrystalline diamond films deposited on silicon: Hydrogen bonding and thermal enhanced carbide formation

The influence of high temperature annealing up to 1200 °C in vacuum on ∼100 nm nearly continuous thick diamond films consisting of 30–50 nm crystallites, deposited onto silicon substrates is reported. The hydrogen bonding and phase composition of the films were studied with Raman spectroscopy, while the surface microstructure and composition were studied with high resolution scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS), respectively. Annealing to 800–900 °C of ∼100 nm thick films results in a decrease in the intensities of the peaks associated with hydrogen bonding (Raman), as well as changes to the morphological microstructure at the film surface. Heating the films to 1000 °C resulted in the complete disappearance of the Raman peaks associated with hydrogen bonding at grain boundaries, and an increase in the relative intensity of the diamond peak relative to the graphite-related D and G Raman peaks, concomitant with changes to the ...

Improving replica exchange using driven scaling

Replica exchange is a powerful simulation method in which simulations are run at a series of temperatures, with the highest temperature chosen so phase space can be sampled efficiently. In order for swaps to be accepted, the energy distributions of adjacent replicas must have some overlap. This can create the need for many replicas for large systems. In this paper, we present a new method in which the potential energy is scaled by a parameter, which has an explicit time dependence. Scaling the potential energy broadens the distribution of energy and reduces the number of replicas necessary to span a given temperature range. We demonstrate that if the system is driven by the time-dependent potential sufficiently slowly, then equilibrium is maintained and energetic and structural properties are identical to those of conventional replica exchange. The method is tested using two systems, the alanine dipeptide and the trpzip2 polypeptide, both in water.

Thermal transport in CO2 laser irradiated fused silica: In situ measurements and analysis