The authors wish to retract this paper1 due to overlap of content with their previously published paper in Advanced Materials,2 including duplicated SEM images and measurement data. The regrettable mistake was a result of mishandling of experimental data with high resemblance. For that, the authors apologize to the readers and the editorial office of Applied Physics Letters for any confusion caused.

1.
C. H.
Chang
,
P.
Yu
, and
C. S.
Yang
,
Appl. Phys. Lett.
94
,
051114
(
2009
).
2.
P.
Yu
,
C.-H.
Chang
,
C.-H.
Chiu
,
C.-S.
Yang
,
J.-C.
Yu
,
H.-C.
Kuo
,
S.-H.
Hsu
, and
Y.-C.
Chang
,
Adv. Mater.
21
,
1618
(
2009
).