Michał Łopuszyński

A comparative DFT study of electronic properties of 2H-, 4H- and 6H-SiC(0001) and SiC(000 \bar{1} ) clean surfaces: significance of the surface Stark effect

The electric field, uniform within a slab, emerging due to Fermi level pinning at both sides of the slab, is analyzed using DFT simulations of SiC surface slabs of different thicknesses. It is shown that for thicker slabs the field is nonuniform and this fact is related to the surface state charge. Using the electron density and potential profiles, it is proved that for high-precision simulations it is necessary to take into account a sufficient number of SiC layers. We show that the use of 12 diatomic layers leads to satisfactory results. It is also demonstrated that the change of the opposite side slab termination, both by different types of atoms or by their location, can be used to adjust the electric field within the slab, creating a tool for simulation of surface properties, depending on the doping in the bulk of the semiconductor. Using these simulations, it was found that, depending on the electric field, the energy of the surface states changes in a different way than the energy of the bulk states. This criterion can be used to distinguish Shockley and Tamm surface states. The electronic properties, i.e. energy and type of surface states of the three clean surfaces: 2H-, 4H-, 6H-SiC(0001) and SiC(), are analyzed and compared using field-dependent DFT simulations.Electric field, uniform within the slab, emerging due to Fermi level pinning at its both sides is analyzed using DFT simulations of the SiC surface slabs of different thickness. It is shown that for thicker slab the field is nonuniform and this fact is related to the surface state charge. Using the electron density and potential profiles it is proved that for high precision simulations it is necessary to take into account enough number of the Si-C layers. We show that using 12 diatomic layers leads to satisfactory results. It is also demonstrated that the change of the opposite side slab termination, both by different type of atoms or by their location, can be used to adjust electric field within the slab, creating a tool for simulation of surface properties, depending on the doping in the bulk of semiconductor. Using these simulations it was found that, depending on the electric field, the energy of the surface states changes in a different way than energy of the bulk states. This criterion can be used to distinguish Shockley and Tamm surface states. The electronic properties, i.e. energy and type of surface states of the three clean surfaces: 2H-, 4H-, 6H-SiC(0001), and SiC(

Composition dependence of elastic constants in wurtzite AlGaInN alloys

000 \bar{1}

Ordering in ternary nitride semiconducting alloys

) are analyzed and compared using field dependent DFT simulations.

Unsupervised Keyword Extraction from Polish Legal Texts

In this paper, we analyze the dependence of elastic constants cij on composition for random wurtzite quaternary AlxGayIn1-x-yN alloy in the whole concentration range. The study takes as its starting point the cij parameters for zinc blende phase calculated earlier by the authors on the basis of valence force field model. To obtain the wurtzite constants from cubic material parameters the Martin transformation is used. The deviations from linear Vegard-like dependence of cij on composition are analyzed and accurate quadratic fits to calculated moduli are presented. The influence of nonlinear internal strain term in the Martin transformation is also investigated. Our general results for quaternary AlxGayIn1-x-yN alloys are compared with the recent ab initio calculations for ternaries GaxIn1-xN and AlxIn1-xN (Gorczyca and Łepkowski, Phys. Rev. B 83 203 201, 2011) and good qualitative agreement is found.

Tagging Scientific Publications Using Wikipedia and Natural Language Processing Tools

We present a thorough theoretical study of ordering phenomena in nitride ternary alloys

Computational study of structural and elastic properties of random AlxGayIn1 − x − yN alloys

{\mathrm{Ga}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{N}

Towards Meaningful Maps of Polish Case Law

,

Towards robust tags for scientific publications from natural language processing tools and Wikipedia

{\mathrm{Al}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{N}

Application of Topic Models to Judgments from Public Procurement Domain

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Monte Carlo studies of ordering in nitride ternary alloys

{\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}