JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

Low Temperature Ion Channeling of Fe2MnSi Film
Epitaxially Grown on Ge(111)
Y. Maeda a, b) , K. Narumi b) , Y. Terai c) , T. Sadoh d) and M. Miyao d)
a) Kyoto University, b) Advanced Science Research Center, JAEA,
c) Osaka University, d) Kyushu University
A full Heusler alloy L2 1-Fe 2MnSi is important for a spin
polarized metal electrode (a spin injector) toward realization
of a spin filed effect transistor: Spin-FET 1, 2) . The perfect
atomic rows along the direction consist of periodic
intervals of Fe(A), Mn(B), Fe(C), Si(D) in the L2 1 lattice.
According to theoretical calculation of magnetic properties
of Fe 2MnSi, perfect spin polarization (half metallicity) may
be affected by actual occupation behavior of Mn atoms at
the B site because the B site atom dominates electronic spin
states near the Fermi level. Since 2007, we have
successively investigated axial orientation and perfection of
DO 3-Fe 3Si, Fe 4Si 2) , L2 1-Fe 2MnSi with some compositions,
Fe 2CoSi, Co 2MnSi films epitaxially grown on Ge(111)
substrate. We found both cases that a lattice mismatch
with the Ge substrate dominated axial orientation as
observed in Fe 2MnSi 4) and that the nearest neighbor atoms
around the B site or (A, C) site dominate chemical bond
strength and stability of axial orientation as in Fe 2CoSi.
In this study following on the previous work, we
investigate the axial orientation at the epitaxial interface of
Fe 2MnSi(111)/Ge(111), then discuss the results taking into
account the results on ion channeling at low temperature,
where we can pass over effect of lattice vibrations on the
axial orientation.
The epitaxial Fe 2MnSi layers with a thickness of ~50 nm
were grown by low temperature- molecular beam epitaxy
(MBE) on n-type Ge(111) substrates at 200 o C 5) . The three
elements of Fe, Mn, and Si were co-evaporated with
Knudsen cells. The axial channeling measurement and
Rutherford backscattering spectroscopy (RBS) for analysis
of composition of alloy films were carried out at either SC1
or MD2 beam lines in TIARA. The channeling
Normalized Yield
Normalized Yield
4-17
1.000
0.100
300K
=0.85
1/2 1/2 1/2 1/2 1/2 1/2
JAEA-Review 2010-065
1.000
0.100
=0.045
min =0.037
min =0.045 =0.037
min =0.045 min
min =0.037
110K
measurement using 2.0 MeV- 4 He + ions and a backscattering
angle of 165 degrees was carried out at 300 K, 110 K and
40 K. The samples were mounted on a cooled holder.
Figure 1 shows angular yield profiles obtained by RBS at
300, 110, and 40 K. We observed evident channeling
along the Ge axis and obtained the minimum yield at
the interface min = 0.045, 0.037 and 0.023, and the critical
angle 1/2 = 0.85, 0.94 and 1.04 degrees at each temperature.
Considering the previous results that their axial
channeling at the interface of Fe 3-xMn xSi/Ge was affected by
the lattice mismatch ratio which increased by increase of Mn
content, the better channeling behavior observed at low
temperature may be attributed to decrease in the lattice
mismatch caused by thermal expansion. Actually, the
lattice mismatch ratios calculated from thermal expansion
data between Fe 2MnSi 6) and Ge 7) are 0.27% at 300 K,
0.15% at 110 K and 0.10% at 40 K. The channeling
behavior being dependent upon the composition and
temperature teaches us that the most dominant factor of the
axial orientation at the interface is the lattice mismatch
between Fe 2MnSi and Ge.
References
1) K. Hamaya et al., Phys. Rev. Lett. 102 (2009) 137204.
2) M. Miyao et al., Thin Solid Films. 518 (2010) S273.
3) Y. Maeda et al., Appl. Phys. Lett. 91 (2007) 17191.
4) Y. Maeda et al., MRS Proc. 1119E (2009) 1119-L05-02.
5) K. Ueda et al., Appl. Phys. Lett. 93 (2008) 112108.
6) G. D. Mukherjee et al., Physica B 254 (1998) 223.
7) O. Madelung, Semiconductors: Data Handbook, 3rd ed.
Springer, 2003, Berlin, p.47.
=0.94
1/2
0.010
0.010
-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4
0.01
-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4
0.01
-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4
0.01
-4 -3 -2 -1 0 1 2 3 4
-4 -3 -2 -1 0 1 2 3 4
Tilt Angle (degree) Tilt angle (degree)
1
0.1
40K 40 K
=0.023
min
=1.04 deg
1/2
Fig. 1 Angular yield profiles along the Ge axis of Fe 2MnSi/Ge(111) obtained at 300, 110, and 40 K.
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