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1

Resonant Photoemission Spectroscopy Study on the Contribution of the Yb 4f States to the Electronic Structure of ZnO

100%

Demchenko I., Melikhov Y., Konstantynov P., Ratajczak R., Barcz A., Guziewicz E.

Acta Physica Polonica A

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2018

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vol. 133

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issue 4

907-909

EN

The electronic structure of Yb implanted ZnO has been studied by the resonant photoemission spectroscopy. The contribution of the Yb 4f partial density of states is predominant at binding energy about 7.5 and ≈11.7 eV below the VB maximum. At photon energy about 182 eV the multiplet structure around 11.7 eV shows the strongest resonance that corresponds to the ¹I multiplet which is almost exclusively responsible for this resonance, while ³H and ³F states are responsible for the resonance around 7.5 eV. It was also found that the Yb 4f partial density of states distribution shows some similarity to Yb₂O₃.

2

X-Ray Absorption Studies of Ge Layers Buried in Silicon Crystal

100%

Demchenko I., Ławniczak-Jabłońska K., Zhuravlev K., Piskorska E., Nikiforov A., Welter E.

Acta Physica Polonica A

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2002

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vol. 101

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issue 5

709-717

EN

Polarization-dependent X-ray absorption spectroscopy was used to study the local microstructure of Ge layers buried in silicon. The layers with thickness from 6 to 20 monolayers of Ge were grown by molecular beam epitaxy on Si substrate and were covered by Si (20 nm). To investigate the morphology of grown structures, X-ray absorption near edge structure and extended X-ray absorption fine structure analysis of the Ge K-edge was done. The performed qualitative analysis proves that X-ray absorption spectra are very sensitive to the local order in the formed structures and are sources of unique information about morphology of the buried Ge layers. Using these techniques we were able to observe the changes in atomic order around the Ge atoms in investigated buried layers and compare the formed atomic order with that in crystalline Ge. A substantial increase in intensity, broadening and chemical shift of the X-ray absorption near edge structure spectrum for 8 ML were observed. It can be related to the increase in density of electron states caused by increase in the localization of the states due to potential appearing at the Ge island boundaries and indicated the formation of quantum dots. The observed in-plane modulations of radial distribution and out-of-plane for different layers were discussed.

3

XANES Studies of Mn K and L_{3,2} Edges in the (Ga,Mn)As Layers Modified, by High Temperature Annealing

84%

Wolska A., Lawniczak-Jablonska K., Klepka M., Jakieła R., Demchenko I., Sadowski J., Holub-Krappe E., Persson A., Arvanitis D.

Acta Physica Polonica A

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2008

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vol. 114

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issue 2

357-366

EN

Ga_{1-x}Mn_xAs is commonly considered as a promising material for microelectronic applications utilizing the electron spin. One of the ways that allow increasing the Curie temperature above room temperature is to produce second phase inclusions. In this paper Ga_{1-x}Mn_xAs samples containing precipitations of ferromagnetic MnAs are under consideration. We focus on the atomic and electronic structure around the Mn atoms relating to the cluster formation. The changes in the electronic structure of the Mn, Ga and As atoms in the (Ga,Mn)As layers after high temperature annealing were determined by X-ray absorption near edge spectroscopy. The experimental spectra were compared with the predictions of ab initio full multiple scattering theory using the FEFF 8.4 code. The nominal concentration of the Mn atoms in the investigated samples was 6% and 8%. We do not observe changes in the electronic structure of Ga and As introduced by the presence of the Mn atoms. We find, in contrast, considerable changes in the electronic structure around the Mn atoms. Moreover, for the first time it was possible to indicate the preferred interstitial positions of the Mn atoms.

4

(Eu,Gd)Te - MBE Growth and Characterization

68%

Dziawa P., Taliashvili B., Domuchowski W., Łusakowska E., Arciszewska M., Demchenko I., Dobrowolski W., Dybko K., Fedorych O., Nadolny A., Osinniy V., Petrouchyk A., Story T.

Acta Physica Polonica A

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2004

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vol. 106

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issue 2

215-221

EN

Monocrystalline thin layers of (Eu,Gd)Te, n-type ferromagnetic semiconductor, were grown by molecular beam epitaxy technique on BaF_2 (111) substrates. Reflection high-energy electron diffraction, X-ray diffraction, and atomic force microscopy characterization proved epitaxial mode of growth and high crystal quality of the layers. Magnetic susceptibility and magnetic resonance measurements showed that in (Eu,Gd)Te layers ferromagnetic transition takes place at about 13 K. Electrical characterization carried out by the Hall effect and resistivity measurements revealed very high electron concentration of 10^{20}~cm^{-3} and sharp maximum of resistivity at transition temperature.

Refine search results

Resonant Photoemission Spectroscopy Study on the Contribution of the Yb 4f States to the Electronic Structure of ZnO

X-Ray Absorption Studies of Ge Layers Buried in Silicon Crystal

XANES Studies of Mn K and L_{3,2} Edges in the (Ga,Mn)As Layers Modified, by High Temperature Annealing

(Eu,Gd)Te - MBE Growth and Characterization