
A : Magnetic contrast

P : Spin-polarization of electrons

A  P M
two properties

M : Magnetization of surface
Polarized
electrons
SPLEEM Image

High spin-polarization,
P
Co : 4 ML

High brightness
M
W(110)
2 m
Conventional electron beam for SPLEEM:
Spin-polarization=20~30%
Brightness=1103 Acm-2sr-1
Exposure time=1-10 s
Real-time imaging with a high contrast:
Spin-polarization >80%
Brightness >3105 Acm-2sr-1
Exposure time< 0.03 s
Conduction band
Circularly-polarized
light
Band splitting
Heavy hole band
Light hole band
Γ-point
Up-spin electron
Γ-point
Down-spin electron
In GaAs type semiconductor, the heavy hole band and the light hole band degenerate
at -point
-point and both up- and down-spin electrons are excited simultaneously by
circularly polarized light.
If the valence bands are split, one type of electrons can be excited selectively.
Spin-polarized
electrons
Circularly
polarized light
92%
GaAs/GaAsP
superlattice 12 pair
GaAsP buffer layer
GaAs substrate
T. Nakanishi, Proceedings of LINAC (2002) 813.
=
S

I: Electron beam current
S: Electron generation area
: Electron beam solid angle
High brightness is obtained by reducing electron generation area.
New transmission-type

The pump laser light is difficult to be
focused, and the electron generation
area is large.
1~2 m
The pump laser light can be highly
focused, and the electron generation
area is very small.
2.26 eV
1.4~1.8 eV
、
GaAs/GaAsP
strained superlattice
12 pair
Growth method: MOVPE,
Growth temperature：660C,
Reactor pressure: 76 Torr,
GaAsP buffer layer
V/III: 15,
GaAs or AlGaAs
inter-layer
Source materials：TEG, TBP, TBA.
GaP substrate
Flow rates:
For GaAs,
TEG: 9.5 mol/min,
TBA: 143 mol/min.
For GaAsP,
TEG: 9.5 mol/min,
TBA: 28 mol/min,
TBP: 114 mol/min.
III type
V type
H2 Gas
Sample
Reactor
Laser light
Photocathode
Electron beam
：
Without inter-layer
ＴＥＭ
g [004]
GaAs
GaAs/GaAsP
superlattice
GaAsP
GaAsP buffer
Thickness modulation50 nm
GaP substrate
100 nm
With inter-layer
GaAs/GaAsP
superlattice
ＴＥＭ
g [004]
GaAsP buffer
GaAs inter-layer
GaP substrate
100 nm
X.G. Jin et al. JAP 108 (2010) #094509
Without inter-layer
％
X.G. Jin et al. APEX 1 (2008)
#045002
2
2
2
I: electron beam current
r: electron beam source radius on photocathode
R: electron beam radius
L: length between photocathode and knife
Laser spot image on
photocathode back side
Laser spot profile
FWHM
1.3 m
1.9 mm
10 m
-2
-1
0
1
Position (m)
1.3 m
1.9 mm
7
-2
3.2 A
-1
2
1 m
M. Suzuki et al. APEX 3 (2010) #026601
Ni Layer = 2 ML
ML、Co Layer = 1 ML
ML。
視野径 (FoV) = 6 m。
画像取得時間 = 0.62秒。
SPLEEM動画
1 m
Ni Layer 2 ML; Co Layer 1 ML
Ni
[110]
Co
Ni
Co
Ni
Co
M. Kuwahara, S. Kusunoki, X.G. Jin et al.
Appl. Phys. Lett. 101 (2012) #033102.
100 nm
T.M aruyam a et al.,
A P L 85 (2004) 2640.
GaAs (4 nm)/
GaAs0.62P0.38 (4 nm )
Superlattice
12 pair~ 90 pair
Growth method: MOVPE,
Growth temperature：660C,
Reactor pressure: 76 Torr,
V/III: 15,
Al0.1Ga0.9As0.81P0.19
buffer layer
Source materials：TEG, TBP, TBA,
Flow rates:
For GaAsP,
For GaAs,
TEG: 9.5 mol/min, TEG: 9.5 mol/min,
TBA: 143 mol/min. TBA: 28 mol/min,
TBP: 114 mol/min.
X.G. Jin et al. APEX 6 (2012) #015801
250
250
200
200
150
150
100
100
50
50
0
600
650
700
750
800
850
0
600
650
700
750
800
850
5
5
5
7
-2
-1