Strain Induced Electronic and Optical Properties of 2D Silicon Carbide Monolayer Using Density Functional Theory

Using the first principle calculation, we investigated the structural, electronic, and strain-dependent optical properties of the two-dimensional hexagonal Silicon Carbide (SiC) Monolayer. We found that the biaxial compressive strain loading gradually changes the direct bandgap SiC into indirect bandgap semiconductor. The compressive strain increases the bandgap but reduces the values of static dielectric constant and refractive index. Conversely, the biaxial tensile strain loading decreases the bandgap but increases the value of static dielectric constant and refractive index. The result shows that the electronic and optical properties of SiC can be engineered to the desired value by applying strain. The large bandgap issue for the SiC monolayer is limiting its uses in different applications which can be overcome with the help of biaxial strain.

On the dielectric constant of titanium dioxide

Conductive rutile TiO2 has received considerable attention recently due to a number of applications. However, the static dielectric constant in conductive, reduced or doped TiO2 appears to cause controversy with reported values in the range 100-10000. In this work, we propose a method for measurements of the dielectric constant in conductive, n-type TiO2 that involves: (i) hydrogen implantation to form a donor profile at a known depth, and (ii) capacitance-voltage measurements for donor profiling. We can not confirm the claims stating an extremely high dielectric constant. On the contrary, the dielectric constant of conductive, reduced rutile TiO2 is similar to that of insulating rutile TiO2 established previously, with a Curie-Weiss type temperature dependence and the values in the range 160-240 along the c-axis.

Comment on “investigation of dielectric constants of water in a nano-confined pore” by H. Zhu, F. Yang, Y. Zhu, A. Li, W. He, J. Huang and G. Li, RSC Adv., 2020, 10, 8628

Neglects of inherent anisotropy and distinct dielectric boundaries may lead to completely erroneous results. We demonstrate that such mistakes can give rise to gross underestimation of the static dielectric constant of cylindrically nanoconfined water.

Simple corrections for the static dielectric constant of liquid mixtures from model force fields

A correction scheme to improve predictions of dielectric constants of liquid mixtures from pair-wise additive force fields that considers electronic polarizability contributions and charge scaling.

Influence of Isotopologue Dipole Moments on Precision Dielectric-Constant Measurements

Measurements of the relative permittivity (static dielectric constant) of fluids such as methane have been interpreted with the assumption of zero dipole moment. This assumption is not strictly true, due to the presence of isotopologues with small, nonzero dipole moments. We investigate the significance of this effect by analyzing the effect of the dipole of CH3D on the static dielectric constant of methane. It is found that the isotopologue effect is more than two orders of magnitude smaller than the uncertainty of the best existing measurements. Similar estimates for other compounds such as H2 and CO2 produce even smaller effects. Therefore, the interpretation of these measurements with a dipole moment of zero remains valid.

Low value for the static background dielectric constant in epitaxial PZT thin films

Ferroelectrics are intensively studied materials due to their unique properties with high potential for applications. Despite all efforts devoted to obtain the values of ferroelectric material constants, the problem of the magnitude of static dielectric constant remains unsolved. In this article it is shown that the value of the static dielectric constant at zero electric field and with negligible contribution from the ferroelectric polarization (also called static background dielectric constant, or just background dielectric constant) can be very low (between 10 and 15), possibly converging towards the value in the optical domain. It is also found that the natural state of an ideal, mono-domain, epitaxial ferroelectric is that of full depletion with constant capacitance at voltages outside the switching domain. The findings are based on experimental results obtained from a new custom method designed to measure the capacitance-voltage characteristic in static conditions, as well from Rayleigh analysis. These results have important implications in future analysis of conduction mechanisms in ferroelectrics and theoretical modeling of ferroelectric-based devices.