ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012) P 55
Mn
4Si
7NANOINCLUSIONS IN Mn-IMPLANTED Si
P. Romanowski1, J. B¸ak-Misiuk1∗, K. Sobczak1, P. Dziawa1, E. Dynowska1, A. Szczepa´nska1, and A. Misiuk2
1Institute of Physics, Polish Academy of Sciences, al. Lotnik´ow 32/46, PL–02668 Warsaw, Poland
2Institute of Electron Technology, al. Lotnik´ow 32/46, PL–02668 Warsaw, Poland Keywords: Si:Mn, synchrotron radiation, annealing, Mn4Si7, nanoinclusions,
ferromagnetism, X-ray diffraction, TEM
∗e-mail : bakmi@ifpan.edu.pl
Among variety of materials silicon is very impor- tant from the viewpoint of the device integration.
Recently it has been suggested that manganese sili- cide nanoparticles created in silicon implanted with manganese and next annealed at high temperatures show ferromagnetism [1]. In present work the influ- ence of annealing conditions on creation of Mn4Si7
nanoinclusions and ferromagnetic behavior of Mn+- implanted silicon (Si:Mn) was studied.
Czochralski p-type 001-oriented Si (Cz-Si) as well as Floating zone n-type 001-oriented Si (Fz-Si) single crystals were implanted with 160 keV Mn+ ions to a dose 1 × 1016 cm−2. To avoid amorphiza- tion, the temperature of the surface during the im- plantation was set to 610 K. Such a fluence of Mn ions results in the dopant concentration of 1.2 at. % at the maximum of Mn distribution profile. Next the samples were processed for 1 h up to 1070 K under ambient pressure.
To investigate phase composition of the near- surface implanted layer, glancing incidence diffrac- tion and synchrotron radiation were applied. It was found that nanoparticles of Mn4Si7phase were cre- ated by post-implantation high-temperature treat- ment.
The dimensions and concentration of the defects related with the silicides inclusions were calculated from the X-ray diffuse scattering observed in diffrac- tion rocking curves, measured using synchrotron radiation [2, 3]. The double logarithmic plot of in- tensity versus the position of q indicate three differ- ent regions with slope −2 (Huang scattering), −3 (Stokes-Wilson scattering) and −2 (thermal scat- tering), respectively (see Fig. 1). The observed silicides are responsible for the Huang diffuse scat- tering very close to the Bragg peak. By study of slopes and transitions from the regions, the dimen- sions and concentration of the inclusions were as- signed according to the method described in [3]. It was found that the sizes of the inclusions increase with the annealing temperature while their concen- tration decreases.
The dimensions of inclusions were also deter- mined by transmission electron microscopy (TEM)
method and compared with X-ray diffraction meth- ods.
Magnetic properties of the Si:Mn samples were studied using SQUID magnetometer device. The origin of ferromagnetism is discussed in conjunction of the nanoinclusions.
Figure 1 : The double logarithmic plot of diffraction rocking curve measured for Cz-Si:Mn annealed at 870 K.
Acknowledgments: The authors thank Dr. Wolfgang Caliebe of HASYLAB at DESY in Hamburg for tech- nical support during the diffraction measurements at W1/DORIS synchrotron beamline.
References
[1] S. Yabuuchi, H. Kageshima, Y. Ono, M. Nagase, A. Fujiwara, E. Ohta, “Origin of ferromagnetism of MnSi1.7nanoparticles in Si: First-principles calcula- tions,” Phys. Rev. B 78 (2008) 045307.
[2] J.R. Patel, “X-ray diffuse scattering from silicon con- taining oxygen clusters,” J. Appl. Cryst. 8 (1975) 186 – 191.
[3] M. Moreno, B. Jenichen, V. Kaganer, W. Braun, A.
Trampert, L. D¨aweritz, K.H. Ploog, “MnAs nano- clusters embedded in GaAs studied by X-ray diffuse and coherent scattering,” Phys. Rev. B 67 (2003) 235206.
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