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Polish Academy of Sciences

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R. Ratajczak

National Centre for Nuclear Research (PL)


Recent publications
1.  Demchenko I.N., Melikhov Y., Walczak M.S., Ratajczak R., Sobczak K., Barcz A., Minikaev R., Dynowska E., Domagała J.Z., Chernyshova M., Syryanyy Y., Gavrilov N.V., Sawicki M., Effect of rapid thermal annealing on damage of silicon matrix implanted by low-energy rhenium ions, JOURNAL OF ALLOYS AND COMPOUNDS, ISSN: 0925-8388, DOI: 10.1016/j.jallcom.2020.156433, Vol.846, pp.156433-1-10, 2020

Abstract:
The structural, electronic, and magnetic properties of low-energy rhenium implanted c-Si are examined for the first time. The damage created by rhenium ions and the following partial reconstruction of the silicon host matrix after rapid thermal annealing (RTA) are investigated as a function of the fluence. Rutherford backscattering spectrometry (RBS) results reveal that the implanted ions are located in the near-surface region with the distribution maximum at about 23 nm below the surface. The analysis of rhenium-depth distribution using the McChasy code shows that the implanted Re-ions are located in the interstitial lattice positions. The RTA leads to a partial recovery of the silicon crystal structure. According to the RBS results, the formed inclusions are not coherent with the silicon host matrix causing an increase of the lattice distortion. Analysis of channeled RBS/c spectra carried out by the McChasy code revealed different levels of bent channels in damaged regions suggesting bimodal distribution of inclusions in the silicon. Studies of high-resolution X-ray photoelectron spectroscopy (XPS) conducted after the RTA showed the shift of Re 4f7/2 binding energy (BE) by +0.68 and + 0.85 eV with respect to metallic rhenium for the samples with lower/higher fluencies, respectively. Complex XPS, density functional theory (DFT) simulations, and transmission electron microscopy (TEM) data analysis allowed us to conclude that the near-surface layer of the sample (~10 nm) consists of nanoinclusions with cubic and/or hexagonal ReSi. In the middle area of the samples, much larger nanoinclusions (>10/20 nm for higher/lower fluencies, respectively) containing pure metallic rhenium inside are formed. The RTA increases the magnetic moment of the sample with the lower dose nearly 20-fold, whereas in the sample with the higher dose a 3-fold increment is observed only. The magnetic response of the examined systems after the RTA indicates a presence of magnetic interactions between the nanoinclusions resulting in the system exhibiting super-spin glass or super-ferromagnetism.

Keywords:
rhenium-implanted silicon, RBS, XPS, RTA, TEM, DFT

Affiliations:
Demchenko I.N. - Institute of Physics, Polish Academy of Sciences (PL)
Melikhov Y. - IPPT PAN
Walczak M.S. - other affiliation
Ratajczak R. - National Centre for Nuclear Research (PL)
Sobczak K. - other affiliation
Barcz A. - Institute of Physics, Polish Academy of Sciences (PL)
Minikaev R. - other affiliation
Dynowska E. - other affiliation
Domagała J.Z. - Institute of Physics, Polish Academy of Sciences (PL)
Chernyshova M. - Institute of Plasma Physics and Laser Microfusion (PL)
Syryanyy Y. - Institute of Physics, Polish Academy of Sciences (PL)
Gavrilov N.V. - other affiliation
Sawicki M. - other affiliation
2.  Demchenko I.N., Ratajczak R., Melikhov Y., Konstantynov P., Guziewicz E., Valence band of ZnO:Yb probed by resonant photoemission spectroscopy, Materials Science in Semiconductor Processing, ISSN: 1369-8001, DOI: 10.1016/j.mssp.2018.11.037, Vol.91, pp.306-309, 2019

Abstract:
Resonant photoemission spectroscopy (RPES), which is a useful tool for extracting photoemission response of the localized Rare Earth (RE) impurity levels from the host electronic band structure, was used to study ZnO:Yb films. The resonant enhancement of the photoemission signal at binding energy around 7.5 and 11.7 eV was observed when photon energy was tuned to the Yb 4d-4f absorption threshold (182 eV). It was found that the 4f and the valence band (VB) maximum binding energies do not depend on the Yb dose, suggesting that the measurement of only one concentration is sufficient to determine the binding energies of the Yb 4f in the examined system. Subsequent annealing did not change the arrangements of implanted ytterbium atoms in host matrix: the majority of them remain in 3 + state having pseudo-octahedral local arrangement similar to Yb2O3.

Affiliations:
Demchenko I.N. - Institute of Physics, Polish Academy of Sciences (PL)
Ratajczak R. - National Centre for Nuclear Research (PL)
Melikhov Y. - IPPT PAN
Konstantynov P. - Institute of Physics, Polish Academy of Sciences (PL)
Guziewicz E. - Institute of Physics, Polish Academy of Sciences (PL)

Conference papers
1.  Demchenko I.N., Melikhov Y., Konstantynov P., Ratajczak R., Barcz A., Guziewicz E., Resonant Photoemission Spectroscopy Study on the Contribution of the Yb 4f States to the Electronic Structure of ZnO, ACTA PHYSICA POLONICA A, ISSN: 0587-4246, DOI: 10.12693/APHYSPolA.133.907, Vol.133, No.4, pp.907-909, 2018

Abstract:
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 approximate to 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 I-1 multiplet which is almost exclusively responsible for this resonance, while H-3 and F-3 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.

Affiliations:
Demchenko I.N. - Institute of Physics, Polish Academy of Sciences (PL)
Melikhov Y. - other affiliation
Konstantynov P. - Institute of Physics, Polish Academy of Sciences (PL)
Ratajczak R. - National Centre for Nuclear Research (PL)
Barcz A. - Institute of Physics, Polish Academy of Sciences (PL)
Guziewicz E. - Institute of Physics, Polish Academy of Sciences (PL)

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