Supporting information for "Preparation and electrical transport properties of
quasi free standing bilayer graphene on SiC (0001) substrate by H intercalation"
A. OM and AFM images of epitaxial graphene
Fig. S1 shows the OM and AFM images of EG-1#, QFSEG-1#, EG-10#, and
QFSEG-10# samples. Fig. S1(a) shows the OM images of QFSEG-1# sample. The OM
images of EG samples are the same as that of the QFSEG samples. It can be found that the
surface of the QFSEG sample on SiC (0001) substrate is consisted of broad terraces with
widths of ~ 10 μm. Fig. S1(b) and (c) show the AFM roughness and phase images of EG-1#
sample, respectively. The step edges and the terraces of the sample show different phase
contrast, indicating their different layer numbers.1 Combing with the Raman results,
monolayer EG formed on the terrace regions, and bilayer EG on the step edge.2 Wrinkles also
formed on the step edge. Fig. S1(d) and (e) show the AFM roughness and phase images of
QFSEG-1# sample, respectively. Comparison of phase images of QFSEG and EG samples
indicates the layer number is added one after H intercalation, which is consistent with the
Raman results in Fig. 2 and the references.3-9
Fig. S1(f) and (g) show the AFM roughness and phase images of EG-10# sample.
Combing with the Raman results, the sample is consisted of monolayer graphene (terraces),
bilayer graphene (step edges), and zero layer graphene (some part on terraces, white contrast).
Fig. S1(h) and (i) show the AFM roughness and phase images of QFSEG-10# sample. The
different phase contras indicate their layer number inhomogeneity.1
1
(a)
(b)
(c)
(d)
(e)
2
(f)
(g)
(h)
(i)
FIG. S1 OM and AFM roughness and phase images of the EG and QFSEG on SiC (0001). (a) OM
images of QFSEG-1# sample. AFM roughness (b), and phase (c) images of EG-1# sample. AFM
roughness (d), and phase (e) images of QFSEG-1# sample. AFM roughness (f), and phase (g) images
of EG-10# sample. AFM roughness (h), and phase (i) images of QFSEG-10# sample.
B. Raman spectra of epitaxial graphene
Fig. S2 shows the Raman spectra of the EG-1# and EG-6# samples. The defect induced
D-peak of the EG-1# sample is lower than EG-6# sample, indication the fewer defects and
good crystal of EG-1# sample.
3
EG-1#
EG-6#
0.08
Intensity
0.06
0.04
0.02
0.00
1500
2000
-1
2500
3000
Peak shift (cm )
FIG. S2 Raman spectra of EG-1# and EG-6# samples.
C. Simulation details of carrier mobility for the quasi-free standing bilayer graphene
samples
We fit the measured carrier mobility using the equation
1
 1  c1  RP
 gr1
(S1)
Our analysis of Coulomb scattering follows the analysis in Ref. 10, 11. As stated by W. Zhu
et al, for bilayer and trilayer graphene, due to the parabolic band structure, the energy
averaging of the Coulomb scattering time can result in the mobility increasing proportionally
to temperature:   k BT . And for uncorrelated impurities, the mobility is inversely
proportional to the impurity density nimp.11 In Ref. 12, at high temperatures, the average
relaxation time results in the substitution E→kBT which gives the mobility  
8h s2 k B
T,
Z i2 e3 m*nimp
where εs is the permittivity of the semiconductor and Zi is the charge state of the impurity. But
if we fit the mobility using c 
c 
B T
, no good fitting can be reached. Usually
nimp
A  B T
nimp
(S2)
is used for simulation, and A and B are constants.10, 11
The values of A, B, and nimp are not unique due to they are numerator and denominator
4
of the same fraction, respectively. They will show fold change. In the simulation, the value of
B is first calculated by B 
8h s2 k B
, and fine tuning of B values are done in the simulation.
Zi2e3m*
The simulation values of A and B are shown in Table S1.
Table S1. Fitting values of the A and B for the QFSEG samples.
fitting parameter
QFSEG-1# QFSEG-2# QFSEG-5# QFSEG-6# QFSEG-10#
A (1012/(V·s))
14882
15007
15000
15001
15008
B (1012/(V·s·K))
14.8
8.7
7.0
5.9
5.0
References
1
S. Tanabe, Y. Sekine, H. Kageshima, M. Nagase, and H. Hibino, Phys. Rev. B 84, 115458
(2011)
2
C. Yu, J. Li, Q.B Liu, S.B. Dun, Z.Z. He, X.W. Zhang, S.J. Cai, and Z.H. Feng, Appl. Phys.
Lett. 102, 013107 (2013)
3
C. Riedl, C. Coletti, T. Iwasaki, A.A. Zakharov, and U. Starke, Phys. Rev. Lett. 103, 246804
(2009).
4
F. Speck, J. Jobst, F. Fromm, M. Ostler, D. Waldmann, M. Hundhausen, H. B. Weber, and Th.
Seyller, Appl. Phys. Lett. 99, 122106 (2011)
5
C. Virojanadara, R. Yakimova, A.A. Zakharov, and L.I. Johansson, J Phys. D: Appl. Phys. 43,
374010 (2010)
6
S. Forti, K.V. Emtsev, C. Coletti, A.A. Zakharov, C. Riedl, and U. Starke, Phys. Rev. B 84,
125449 (2011).
7
D.Waldmann, J. Jobst, F. Speck, T. Seyller, M. Krieger, H. Weber, Nat. Mater. 10, 357
(2011).
8
J.A. Robinson, M. Hollander, M. LaBella, K.A. Trumbull, R. Cavalero, and D.W. Snyder,
Nano Lett. 11, 3875 (2011).
9
J. Ristein, S. Mammadov, and Th. Seyller, Phys. Rev. Lett. 108, 246104 (2012).
10
W. Zhu, V. Perebeinos, M. Freitag, and P. Avouris, Phys. Rev. B 80, 235402 (2009).
11
S. Xiao, J. Chen, S. Adam, E.D. Williams, and M.S. Fuhrer, Phys. Rev. B 82, 041406(R)
(2010).
5
12
D. Ferry, Transport in Nanostructure, Cambridge University Press, Cambridge, England,
(2009) Chap. 2
6