acta physica slovaca

Abstract: The paper deals with structural and electrical properties of original, ion beam, and plasma exposed hydrogenated amorphous silicon (a-Si:H) surface. The a-Si:H semiconductor forms the intrinsic layer in amorphous silicon solar cells whose performance depends on the defect distribution, particularly on the density of dangling bonds. Device-quality intrinsic a-Si:H layer of approx. 1~$\mu $m thickness was deposited on n-type Si(100) oriented crystals in 13,56~MHz rf excited parallel plate plasma enhanced chemical vapor deposition system. Two types of surface exposures were made: by oxygen and argon plasmas. The Ar plasma-damaged surfaces were covered by an oxide layer prepared by \textit{in-situ} exposure to pure oxygen atmosphere. In all cases, an uppermost very thin oxide overlayer of 5--10~nm thickness was formed, thicker than the native oxide formed after the PECVD of the amorphous layer. The optical and structural properties of original and damaged surfaces were investigated by reflectance spectroscopy and X-ray diffraction at grazing incidence, respectively. An important transformation of structural properties of a{\-}Si:H~ on Si(100) was investigated via the evolution of diffraction pattern around 2$\Theta $~=~28.5\r{ }. Electrical properties were determined by the charge version of deep level transient spectroscopy, C-V and I-V measurements. Bias annealing procedures lead to the a MIS structure without deep states at the interface. The results obtained are compared with these measured on ion beam exposed a-Si:H surfaces [V. N\'{a}da\v{z}dy, R. Durn\'{y}, E. Pin\v{c}\'{\i}k, Phys. Rev. Letters \textbf{78}; 1102 (1997)].

Abstract: This letter presents a calculation of periastron shift in an astrophysical binary in which a non-spinning body moves in a slightly deformed circle round a slowly spinning central body. The equation of motion followed in the calculation was derived earlier by Faruque using relativistic effective one-body dynamics. The results show a clear dependence of periastron shift on magnitude as well as on direction of spin and orbital angular momentum of the central body and the orbiter, respectively, and this dependence is in accord with previous results found by a different procedure by other authors.

Abstract: We will show how to project two-photon polarization states onto symmetric and antisymmetric subspaces of Hilbert space with the use of linear optics and postselection only. It enables to measure the overlap between photon polarization states. Our scheme is based on quantum teleportation and succeeds with the probability of $1 \mathord{\left/ {\vphantom {1 8}} \right. \kern-\nulldelimiterspace} 8$.

Abstract: A bound on the $\nu_{\tau}$ magnetic moment is calculated through the reaction $e^{+}e^{-}\rightarrow \nu \bar \nu \gamma$ at the $Z_1$-pole, and in the framework of a left-right symmetric model at LEP energies. We find that the bound is almost independent of the mixing angle $\phi$ of the model in the allowed experimental range for this parameter.

Abstract: The present study investigates the log(ft) values of the allowed $\beta^{\pm}$ decay between odd-A deformed nuclei in the atomic mass regions of $125\leq A\leq131$ and $159\leq A\leq181$. Single particle energies and wave functions have been calculated with a deformed Woods-Saxon potential. Calculations have been performed within the framework of a proton-neutron quasi-particle random phase approximation (QRPA), including the schematic residual spin-isospin interaction between nucleons in the particle-hole and particle-particle channels. It has been seen that the results obtained by using the values for the fixed particle-hole and particle-particle interaction strengths, $\chi^{ph}_{GT}=5.2/A^{0.7}$ $MeV$ and $\chi^{pp}_{GT}=0.58/A^{0.7}$ $MeV$, have good agreement with the experimental observations.

Abstract: Temperature dependence of London penetration depth of nonmagnetic borocarbides YNi$_{2}$B$_{2}$C is studied in the framework two-band Ginzburg-Landau theory. Its temperature dependence is non-linear near T$_{c}$. The strength of the non-linearity is mainly dependent on the interaction coupling between the order parameters of two separate bands. In addition, the inter-gradient interaction as well as the ratio of effective masses of two separate bands was also found to be important in determining its temperature dependence. The results of the calculations are in good agreement with the experimental data for bulk YNi$_{2}$B$_{2}$C.

Abstract: The complex geometric setup around the SONG CsI scintillator aboard the CORONAS-I satellite has been modelled, to evaluate the mass thickness passed through by the cosmic ray particle striking the detector. The analytic functional form giving the amount of matter traversed in absorbers for an arbitrary incident directions is present. The population mean and variance of the mass thickness are estimated by random sampling of the uniformly distributed particle trajectories in the several solid angles.