Liviu Bilteanu | Searcharxiv

arXiv2012

Friedel oscillations at the Dirac-cone-merging point in anisotropic graphene

We study the Friedel oscillations induced by a localized impurity in anisotropic graphene. We focus on the limit when the two inequivalent Dirac points merge. We find that in this limit the Friedel oscillations manifest very peculiar features, such as a strong asymmetry and an atypical inverse square-root decay. Our calculations are performed using both a T-matrix approximation and a tight-binding exact diagonalization technique. They allow us to obtain numerically the local density of states as a function of energy and position, as well as an analytical form of the Friedel oscillations in the continuum limit. The two techniques yield results that are in excellent agreement, confirming the accuracy of such methods to approach this problem.

cond-mat.mes-hall↗

arXiv2011

Hydrogen Diffusion in Silicon - An ab initio Study of Hydrogen Kinetic Properties in Silicon

In this paper we present kinetic properties such as migration and decomposition barriers of hydrogen defects in silicon calculated by Density Functional Theory (DFT) based methods. We study the following defects: H atoms (H) and ions (H+, H-), hydrogen molecules (H2) and hydrogen complexes (H2*). Our results show that the dominating migration species are H ions, their charge-independent migration barrier being 0.46 eV in excellent agreement with experimental value [1]. At higher temperatures H2 and H2* decompose with barriers of 1.2 and 1.5 eV respectively, while the migration barrier of H2 is 2.2 eV. Hence, we show that, contrary to what has been experimentally implied [2, 3] previously, in silicon, hydrogen molecules do not participate to the hydrogen transport through diffusion. 1. A. Van Wieringen and N. Warmoltz, Physica 22, 849 (1956). 2. S. Rao, S. K. Dixit, G. Lupke, N. H. Tolk, and L. C. Feldman, Physical Review B 75, 6 (2007). 3. N. Fukata, A. Kasuya, and M. Suezawa, Physica B 308, 1125 (2001).

cond-mat.mtrl-sci↗