of 5
Supplementary Information
Direct Large-Area Growth of Graphene on Silicon for Ultra-
Low-Friction and Silicon-Based Technologies
Wei-Shiuan Tseng
1,2
, Yen-Chun Chen
3
, Chen-Chih Hsu
1
, Chen-Hsuan Lu
4
, Chih-I Wu
5
,
and Nai-Chang Yeh
1,
*
1
Department of Physics, California Institute of Technology, Pasa
dena, CA, 91125, USA
2
College of Photonics, National Ch
iao-Tung University, Hsin-Chu
30013, Taiwan
3
Department of Physics, National
Tsing-Hua University, Hsin-Chu
30013, Taiwan
4
Department of Applied Physics and
Materials Science, California
Institute of
Technology, Pasadena, CA 91125, USA
5
Graduate Institute of Photonics and Optoelectronics and Departm
ent of Electrical
Engineering, National Taiwa
n University, Taipei 106, Taiwan
* Corresponding author. Tel: 626 395-4313. E-mail:
ncyeh@caltech.edu
(N.-C. Yeh)
Figure S1
Figure S1: The PECVD setup for direct graphene growth on silico
n, which includes the
plasma generator, growth-tube, v
acuum pumps, mass-flow-control
(MFC) valves, and
different gases for the growth. HF was used to remove native Si
O
2
on the surface of Si
substrates immediately before the
substrates were inserted into
the growth chamber. More
details about our PECVD setup
can be found in References 48 and
49.
Figure S2.
Figure S2: (a) XPS and (b) UPS spectra of graphene nano-walls o
n Si substrates. These
results were very similar to those obtained from horizontal gra
phene sheets on Si substrates.
Figure S3.
Figure S3: Comparison of the RGA records of (a) CO and (b) CO
2
signals taken during the
PECVD growth of graphene on Si and SiO
2
substrates, respectively. Here the sharp rise of
CO and CO
2
signals corresponded to the ti
me when plasma was ignited.
Figure S4.
Figure S4: AFM studies of the cross-sectional profiles of (a) 3
and (b) 14 layers of graphene
sheets grown on Si substrates. A sharp AFM tip was used to make
scratches on graphene
surfaces for cross-sectional studies. Some overshoots were form
ed due to the method used
to create scratches, and so the steps were determined by the me
an heights at distances far
from the cuts.