Oxidation-enhanced thermoelectric efficiency in a two-dimensional phosphorene oxide

We performed density functional theory calculations to investigate the thermoelectric properties of phosphorene oxide (PO) expected to form by spontaneous oxidation of phosphorene. Since thermoelectric features by nature arise from the consequences of the electron-phonon interaction, we computed the phonon-mediated electron relaxation time, which was fed into the semiclassical Boltzmann transport equation to be solved for various thermoelectric-related quantities. It was found that PO exhibits superior thermoelectric performance compared with its pristine counterpart, which has been proposed to be a candidate for the use of future thermoelectric applications. We revealed that spontaneous oxidation of phosphorene leads to a significant enhancement in the thermoelectric properties of n-doped phosphorene oxide, which is attributed to the considerable reduction of lattice thermal conductivity albeit a small decrease in electrical conductivity. Our results suggest that controlling oxidation may be utilized to improve thermoelectric performance in nanostructures, and PO can be a promising candidate for low-dimensional thermoelectric devices.

Miniband Electroconductivity in Superlattices of Cubic Quantum Dots of the InAs/GaxIn1-xAs Heterosystem

In this paper, the model of InAs/GaxIn1-xAs cubic quantum dot superlattices (CQDS) of various dimensionality has been proposed. The energy spectra of electrons and holes of the quantum dot superlattice have been determined in the effective mass approximation and modified Kronig-Penney model. In the frame of this model, the spectra of charges of 3D, 2D and 1D-superlattices can be obtained by changing respective distances between the elements of the superlattice. The energy dependence of the electron and hole subbands (under-the-barrier subbands and over-the-barrier subbands) on the wave vector of the superlattice has been calculated. The number of under-the-barrier subbands is determined by QD size and width of each subband is defined by QD size, distances between superlattice elements and subband numerical index. The dependences of the Fermi energy and concentration of charge carriers on temperature, concentration of impurities, energy of impurity levels have been obtained and analyzed. We have taken account of the dependence of electron relaxation time on temperature caused by scattering of carriers on both phonons and donor centers. The effect of the impurity system on electroconductivity of the CQDS is investigated.