arXiv subjects

F. Maca

Publications and source records attributed to F. Maca.

23 records · Page 2Linked to original sources

arXiv2003

Disorder-Induced Effects in III-V Semiconductors with Mn

The substitution of Mn in the III-V diluted magnetic semiconductors leads to a strong electron scattering on impurities. Besides the features induced in the valence band by the hybridization with the Mn d-states, also the conduction band is affected by the absence of the Mn s-states at its edge. Also the high concentration of compensating donors modifies the band structure. This is shown on the absorption coefficient epsilon2(omega) of GaP doped with Mn and Se. The absorption evaluated by ab initio density functional calculations starts with a smooth tail and does not show the structure typical for III-V materials. We analyze these features and the role of the donors on model systems using the tight-binding coherent potential approach.

cond-mat.mtrl-sci↗

arXiv2003

Lattice constant in diluted magnetic semiconductors (Ga,Mn)As

We use the density-functional calculations to investigate the compositional dependence of the lattice constant of (Ga,Mn)As containing various native defects. The lattice constant of perfect mixed crystals does not depend much on the concentration of Mn. The lattice parameter increases if some Mn atoms occupy interstitial positions. The same happens if As antisite defects are present. A quantitative agreement with the observed compositional dependence is obtained for materials close to a complete compensation due to these two donors. The increase of the lattice constant of (Ga,Mn)As is correlated with the degree of compensation: the materials with low compensation should have lattice constants close to the lattice constant of GaAs crystal.

cond-mat.mtrl-sci↗

arXiv2002

Self-compensating incorporation of Mn in Ga(1-x)Mn(x)As

We consider hypothetical Ga7MnAs8, Ga16MnAs16, and Ga14Mn3As16 crystals with Mn in a substitutional, interstitial, and both positions. Spin-polarized FPLAPW calculations were used to obtain their electronic structure. We show that the interstitial Mn acts as a double donor and compensates the holes created by two Mn atoms in substitutional positions. This explains why the number of holes in Ga(1-x)Mn(x)As is much smaller than x. The presence of interstitial atoms may also be the reason for the lattice expansion with increasing content of Mn. The differences in electronic behavior of substitutional and interstitial Mn are discussed.

cond-mat.mtrl-sci↗

arXiv1999

Energy barriers for diffusion on stepped Rh(111) surfaces

Energy barriers for different moves of a single Rh adatom in the vicinity of steps on Rh(111) surface are studied with molecular statics. Interatomic interactions are modeled by the semi-empirical many-body Rosato-Guillope-Legrand potential. We calculate systematically barriers for the descent at straight steps, steps with the kink and small islands as well as barriers for diffusion along the step edges. The descent is more probable on steps with a {111} microfacet and near kinks. Diffusion along a step with a {100} microfacet is faster than along a step with a {111} microfacet. We also calculate barriers for diffusion on several surfaces vicinal to Rh(111).

cond-mat.mtrl-sci↗

arXiv1998

Energy barriers for diffusion on stepped Pt(111) surface

We performed molecular statics calculations of energy barriers for adatom moves in the vicinity of steps on Pt(111) surface. We used the semi-empirical many-body Rosato--Guillope--Legrand potential and we systematically calculated barriers for descent of straight steps, steps with a kink and small islands as well as barriers for diffusion along the step edges. We confirmed that the lowest barrier for descent is for an exchange process near kink's or island's corner on a step with a {111} microfacet. Diffusion along a step with a {111} microfacet is faster than along a step with a {100} microfacet. We also calculated barriers for diffusion on several surfaces vicinal to Pt(111). Our results are compared with previous calculations.

cond-mat.mtrl-sci↗