In this work an influence of thermal annealing of Mn-implanted silicon on strain state of silicon matrix is presented. During post-implantation annealing, nanocrystalline tetragonal Mn4Si7 compound is formed. A strong correlation between the size of nanoinclusions and the matrix strain state is detected

A Misiuk

J Bak-Misiuk

K Sobczak

P Romanowski

R Jakiela

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Synchrotron Radiation in Natural Science Vol. 12, No. 1 – 2 (2013)
10
Strain state in Mn-implanted silicon annealed at high temperature
P. Romanowski, J. Bak-Misiuk1*, K. Sobczak1, R. Jakiela1, and A. Misiuk2
1 Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02668 Warsaw, Poland
2 Institute of Electron Technology, al. Lotnikow 32/46, PL-02668 Warsaw, Poland
Keywords: Mn-implanted silicon, nanoinclusions, X-ray diffraction
* E-mail address: bakmi@ifpan.edu.pl
In this work an influence of thermal annealing of Mn-implanted silicon on strain state of silicon matrix is 
presented. During post-implantation annealing, nanocrystalline tetragonal Mn4Si7 compound is formed. A
strong correlation between the size of nanoinclusions and the matrix strain state is detected.
1. Introduction
In recent years, much interest has been devoted to 
materials called diluted magnetic semiconductors 
(DMS): mixed crystals based on classic semiconductors, 
with a controlled fraction of nonmagnetic cations 
substituted by the magnetic ones [1]. Silicon-based DMS 
would be the preferred spintronics material due to 
existing technology used in Si-based microelectronics 
and wide availability of high quality Si single crystals. 
Dietl et al. [2] predicted a carrier-mediated 
ferromagnetism for silicon doped with 5 % Mn. For wide 
commercial application room-temperature 
ferromagnetism in DMS is desired. Zhang et al. [3] 
reported the Mn0.05Si0.95 alloy with Curie temperature, TC,
of about 400 K.
Ion implantation is one of the methods utilized to 
achieve ferromagnetic properties of semiconductors. 
Ferromagnetic ordering in Mn-implanted Si has been 
reported recently (e.g. [4-7]. For Si:Mn produced by 
implantation with Mn+ doses, D = 1015 – 1016 cm-2, at 
energy, E = 300 keV, TC exceeds 400 K after its rapid 
thermal annealing at 800°C [4]. Randomly distributed 
Mn atoms play twofold role: promote the formation of 
local magnetic moment and supply free carriers (holes) 
which mediate exchange interaction between the local 
moments). It has been suggested that the ferromagnetic 
exchange is carrier mediated.
However, due to low solubility of Mn in Si and easy 
Mn reaction with Si, the formation of manganese silicide 
in Mn-implanted Si is often observed. It has been found 
that high-temperature-pressure annealing of Si:Mn 
produced by implantation results in a creation of Mn4Si7
inclusions [8,9]. However, these Mn4Si7 nanoinclusions 
in Si show ferromagnetism with magnetic moment higher 
than that of the bulk (TC ≈ 45 K, according Ko et al. 
[10]). Therefore, the Mn4Si7 phase rather cannot be 
considered as a main source of ferromagnetism at or 
above room temperature. Our last results indicate on an 
influence of the Mn4Si7/Si interface on magnetic ordering 
of Mn+-implanted silicon [9].
The inclusions formed during post-implantation 
thermal processing may influence the strain state of the 
crystals (see, e.g. [11]). The aim of the present work is to 
determine the influence of the Mn-containing inclusions 
on the silicon matrix strain state.
2. Experimental
Czochralski and Floating-zone (001)-oriented silicon 
single crystals were implanted with 160 keV Mn+ ions to 
a dose of 1´1016 cm-2. Such implantation causes a 
creation of quasi three-layers structure composed, in 
sequence, of the damaged near-surface Si layer 
(thickness ~100 nm), the Mn-implanted Si layer 
(~50 nm) and the almost undamaged Si substrate. 
Maximum concentration of the Mn-implanted ions equal 
to about 1.2% is observed at the depth of ~140 nm. To 
modify the defect structure of Si:Mn and rebuild the 
damaged material, the samples were annealed for 1 h at 
temperatures up to 800°C under ambient pressure of 
105 Pa. 
The phase composition of polycrystalline layers 
created during the processing at the near-surface areas 
was measured using X-ray diffraction techniques and 
synchrotron radiation. The results presented earlier [8,9] 
showed that Mn-containing nanoinclusions, identified as 
the tetragonal Mn4Si7 compound, are formed. Using 
transmission electron microscopy technique as well as by 
study the slopes of the diffraction rocking curves it has 
been found that the sizes of the inclusions increase with 
annealing temperature, whereas their concentration 
decreases [9].
High-resolution Philips Material Research 
Diffractometer equipped with a standard laboratory 
source of CuKa1 radiation was used to study the strain 
distributions in the silicon matrix. Secondary ion mass 
spectroscopy (SIMS) depth profiles of Mn were 
measured using the CAMECA IMS6F spectrometer.
3. Results
Strain distribution in the Si matrix was determined from 
the analysis of the shape of X-ray diffraction peak. 
Unsymmetrical shape of the 004 X-ray diffraction peaks 
Synchrotron Radiation in Natural Science Vol. 12, No. 1 – 2 (2013)
11
shows on a distribution of the matrix lattice parameter 
(see Fig. 1 and 2). This effect is the same for Czochralski 
and Floating-zone Si:Mn samples and disappears after 
800°C processing. For this temperature the particle sizes 
exceed 20 nm [9]. These particles become incoherent in 
respect to the silicon matrix and so strain disappears (the 
tensile strain occurs below the 15 nm size).
Simultaneously, the SIMS technique showed that the 
diffusion of Mn ions in effect of temperature processing 
was insignificant (Figs 3 and 4). It means that there exists 
a strong correlation between the size of nanoinclusions 
and the matrix strain state. 
Numerical simulation of the X-ray diffraction peaks,
using the Epitaxy 4.0 made Panalytical B.V by softwer,
has been performed and depth distribution of the Si-
matrix strain has been obtained (Fig. 5). The maximum 
strain appears at the depth corresponding approximately 
the maximum Mn concentration. Stress connected with 
the mentioned above Si matrix strain (the Hook law) can 
result in a creation of the inclusion-related strain, e.g.
[11]. Therefore, Mn4Si7 inclusions can be deformed in 
respect to the bulk material. To distinguish this 
possibility, precise measurements of the lattice constant 
of inclusions must be performed in future.
4. Conclusions
Using various experimental methods, including 
synchrotron radiation measurements, correlation between 
dimensions of Mn4Si7 inclusions and strain state of the Si 
matrix was found. It occurred to be possible to find the 
critical values of these dimensions for the case they 
become incoherent in respe ct to the Si matrix.
Figure 1. 2q/w X-ray diffraction patterns (004 Si reflection) 
for Czochralski Si:Mn samples annealed for 1 h at 340°C (1), 
600°C (2) and 800°C (3).
Figure 2. 2q/w X-ray diffraction patterns (004 Si reflection) 
for Floating-zone Si:Mn samples annealed for 1 h at 340°C 
(1), 600°C (2) and 800°C (3).
Figure 3. SIMS Mn depth profiles for Czochralski Si:Mn: 
as-implanted sample (1) as wellas for samples annealed for 1 
h at 600°C (2) and 800°C (3).
Figure 4. SIMS Mn depth profiles for Floating-zone Si:Mn as-
implanted sample (1) as well as for samples annealed for 1 h at 
340°C (2) and 800°C (3).
Synchrotron Radiation in Natural Science Vol. 12, No. 1 – 2 (2013)
12
Figure 5. Numerical simulation of 2q/w X-ray diffraction pattern (upper) and depth distribution of the Si-matrix strain (lower) for
Czochralski Si:Mn sample annealed for 1 h at 340°C.
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Numerical simulations of the X-ray  diffraction peaks have been performed and 


Strain state in Mn-implanted silicon annealed at high temperature

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Strain state in Mn-implanted silicon annealed at high temperature

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