Supplementary materials for
Evidence of the two surface states of (Bi0.53Sb0.47)2Te3 films
grown by van der Waals epitaxy
Liang He,1,* Xufeng Kou,1,* Murong Lang,1,* Eun Sang Choi2, Ying Jiang,3 Tianxiao
Nie,1 Wanjun Jiang1, Yabin Fan1, Yong Wang,3 Faxian Xiu,4 and Kang L. Wang1
1
Department of Electrical Engineering, University of California, Los Angeles, California
90095, USA 2National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
3
Center for Electron MicroscopyandState Key Laboratory of Silicon Materials,
Department of Materials Science and Engineering, Zhejiang University, Hangzhou,
310027, China 4State Key Laboratory of Surface Physics and Department of Physics,
Fudan University, Shanghai 200433, China
*
These authors contribute equally to this work.

To whom correspondence should be addressed. E-mail: [email protected],
[email protected]
Supplementary Information
1. Figure S1| MBE growth of (Bi0.53Sb0.47)2Te3
2. Figure S2| Gate dependent transport measurement of (BixSb1-x)2Te3
for various composition x from 0.32 to 0.77
3. Figure S3| Gate dependent Hall resistance of (Bi0.53Sb0.47)2Te3
4. Figure S4| Resistance vs. Temperature curve of (Bi0.53Sb0.47)2Te3
5. Figure S5| Gate dependent MR of (Bi0.53Sb0.47)2Te3
6. Figure S6| Gate dependent Rxx vs. 1/B
7. Figure S7| Rxx, dRxx/dB and d2Rxx/dB2 as function of B
8. Figure S8| ARPES image of (Bi0.53Sb0.47)2Te3
1
(b)
After 2 QL growth
After growth
After 2 QL growth
After growth
After intermediate anneal
(c)
Before growth
a)
After growth
b)
a0 ( Å )
After 2 QL growth
4.32
4.24
4.16
4.08
4.00
-1
After 2 QL growth
d)
c)
Intensity (a.u)
After 2 QL growth
Before growth
0
1
2
3
Thickness (QL)
4
2
0
163
326
3
4
5
6
489
652
815
978
Time (s)
AfterS1|
growth
Figure
MBE growth of (BixSb1-x)2Te3. (a) RHEED image of GaAs (111)B
substrate after annealed at 580C for 5 min under Se rich environment. A Single
layer of GaSe has formed on the surface. (b) RHEED image after 10 QL
(Bi0.53Sb0.47)2Te3. The d-spacing between the two 1st order streaky lines
(indicated by the double arrows in a and b) has been used to estimate the film
lattice constant. (c) The thickness evolution of lattice constant of a
(Bi0.53Sb0.47)2Te3 film. The lattice relaxation happens within the first QL,
consistent with the van der Waals growth mode. (d) RHEED intensity oscillations
of the specular peak, from which growth rate of 163 s/QL has been estimated.
2
a) 3000
2500
-100
2000
1500
0
0.32
0.41
0.53
0.65
0.77
-200
-300
1000
500
100
0
RH(/T)
Rxx()
b)
0.32
0.41
0.53
0.65
0.77
-400
T = 0.3 K
-500
-10
-5
0
VG(V)
5
10
T = 0.3 K
-10
-5
0
VG (V)
5
10
Figure S2| Gate dependent transport measurements of (BixSb1-x)2Te3 for
various composition x from 0.32 to 0.77. (a) Longitudinal resistance Rxx versus
gate voltage VG. All the samples, except x = 0.77 sample, exhibit ambipolar effect,
suggesting the multiple conducting channels with different carrier type. At VG = 0
V, the samples demonstrate a transition from p-type to n-type as composition x
changes from 0.32 to 0.77. This is consistent with the results of n-type Bi2Te3 and
p-type Sb2Te3 in MBE grown thin films. (b) The Hall slopes of films, also shows a
transition from p-type to n-type dependent on the gate voltage, suggesting a
systematic shifting of Fermi level.
3
15
3
a)
T = 0.3 K
2
10
-1V
-7V
-11V
+1V
0
+2V
1
Rxy (k)
5
Rxy (k)
b)
T = 0.3 K
-5
+1V
0
-7V
-11V
-1V
-1
+2V
+10V
+10V
-10
-15
-40
+4.6V
-20
0
B (T)
20
+7V
-2
+7V
+3V
+4.6V
+4V
+3V
+4V
-3
-6
40
-4
-2
0
B (T)
2
4
6
Figure S3| Gate dependent Hall resistance of (Bi0.53Sb0.47)2Te3. (a) Hall
resistance Rxy at various gate voltages VG. Clearly, the slopes change from
negative to positive as the gate voltages decrease, representing the dominant
carriers change from electrons to holes. The non-linearity of Rxy suggests that
more than one conducting channels exist in the system. (b) Zoom-in view
demonstrates the linear dependence at low magnetic field. The Hall coefficient,
RH,
is
calculated
at
B
=
6
T.
4
3200
3000
7.90
7.85
Ea = 20 meV
Ln(Rxx)()
Rxx (k)
2800
7.80
2600
7.75
7.70
2400
7.65
3.8
4.0
4.2 4.4 4.6
-1
1000/T (K )
4.8
5.0
2200
3
4
5 6 7 89
1
2
3
4
5 6 7 89
10
T (K)
2
3
4
5 6 7 89
100
2
Figure S4| Resistance vs. Temperature curve of (Bi0.53Sb0.47)2Te3. At low
temperature ( T < 1.4 K) Rxx is constant. Top inset: the Arrhenius plot of Ln(Rxx)
vs. 1000/T. The estimated high temperature activation energy is 20 meV.
5
2.5
a)
T = 0.3 K
MR
2.0
3V
b)
3V
T = 0.3 K
1.5
1.0
0.5
-11V
11V
0.0
0
10
20
30
B (T)
40 0
10
20
30
B (T)
40
Figure S5| Gate dependent MR of (Bi0.53Sb0.47)2Te3. Magnetoresistance at
various gate biases. a, As the gate decreases from 11 V to 3 V, the MR
increases and reaches a maximum value at VG = 3 V, where the Rxx also sits
at the peak. b, MR decreases monotonically from 3 V to -11 V. A linear MR
has also been observed at high magnetic field, as indicated by dashed red
lines. It only happens in the region I, where the bulk holes are the majority
carriers.
6
11V
10V
9V
8V
7V
6V
5V
4V
3V
Rxx(a. u.)
2V
1V
0V
-1V
-2V
-3V
-5V
-7V
-9V
-11V
30
40
50
60
70
80
90
100
-1
1000/B (T )
Figure S6| Gate dependent Rxx vs. 1/B. Here, we define Rxx = Rxx - <Rxx>,
where <Rxx> is a smoothed background. Quantum oscillations can be seen.
To make the oscillations more clearly, in the manuscript, we have used the
second derivative of Rxx, d2Rxx/dB2.
7
N
N+2
N+1
n
Rxx
n+1
dRxx/dB
d2Rxx/dB2
B
Figure S7| Rxx, dRxx/dB and d2Rxx/dB2 as function of B . N corresponds to
N-th Landau level that is crossing the Fermi energy EF, while n corresponds
to N+1/2-th Landau level when EF is precisely between adjacent LLs.
It has been a little confusing some people use N and others use n to plot
Landau fan diagram. But most recently, more people adopted n, in which they
assign LL number n to the minimum of Rxx 1-3. In this manuscript, we assigned
n to the maximum of d2Rxx/dB2. This will give us the Onsager equation of
2 (n   )  S F

. And for TI materials ( Berry phase), all the linear fitted
eB
curves should theoretically extrapolate to (0, ½).
8
300
Bottom
200
11V
Top
2V
E-ED (meV)
100
0
-100
-200
-0.2
-0.1
0.0
0.1
-1
K//(Å )
0.2
Figure S8| ARPES image of (Bi0.53Sb0.47)2Te3. The electronic structure of the
(Bi0.53Sb0.47)2Te3 thin film via ARPES. The Dirac cone can be clearly observed.
The Fermi levels of top and bottom surface states extracted from SdH
oscillations are shown in red and blue lines, respectively.
9
1.
2.
3.
Qu, D.-X., Hor, Y.S., Xiong, J., Cava, R.J. & Ong, N.P. Quantum Oscillations and Hall
Anomaly of Surface States in the Topological Insulator Bi2Te3. Science 329, 821-824
(2010).
Analytis, J.G. et al. Two-dimensional surface state in the quantum limit of a topological
insulator. Nat Phys 6, 960-964 (2010).
Ren, Z., Taskin, A.A., Sasaki, S., Segawa, K. & Ando, Y. Large bulk resistivity and surface
quantum oscillations in the topological insulator Bi2Te2Se. Phys. Rev. B 82, 241306
(2010).
10