Supporting information for:
Localized Ultraviolet Photoresponse in Single
Bent ZnO Micro/Nanowires
Ya Yang, Wen Guo, Junjie Qi, Jing Zhao, and Yue Zhang
State Key Laboratory for Advanced Metals and Materials, School of Materials
Science and Engineering, University of Science and Technology Beijing, Beijing
100083, China
E-mail address: yuezhang@ustb.edu.cn
1. The fitted rise and decay time constants of the ZnO wire at the straight and bent
regions
The rise and decay curves in Fig. 4(b) were fitted by the exponential time dependency
I  I 0 [1  exp( t /  rt )] and I I 0 exp( t /  dt ) , respectively. It could be clearly seen that the
ZnO wire has the same rise and decay time at the straight and bent regions.
Figure S1 The fitted time response of the photocurrent from the ZnO wire at the straight
region
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Figure S2 The fitted time response of the photocurrent from the ZnO wire at the bent region.
2. The mechanism of the photoresponse sensitivity enhancement
Although the observed photoresponse enhancement in the ZnO wire at the bent region is
consistent with that in the ZnO field effect transistor (FET) under a gate-bias condition for a
depletion mode, the mechanism of the photoresponse enhancement is still not explained. We
now propose possible mechanisms for explaining the observed phenomenon. The ZnO wire
at the bent regions can be considered as a FET, where the piezoelectric electric filed serves as
the gate electrode. The piezoelectric electric field can trap some free electrons at the outer
surface of the bent ZnO wire [Fig. S3], which can result in the decrease of conductivity of the
ZnO wire. When the UV illumination is focused on the straight region of the bent ZnO
nanowire, the free electrons can also be trapped by the piezoelectric electric field. However,
when the UV is focused on the bent region, the piezoelectric electric field can be screened by
the photogenerated electron-hole pairs [Fig. S4]. Then, the trapped electrons can be released,
which increases the effective carrier density in the ZnO wire. Moreover, the charge depletion
zone will decrease due to the screening of the piezoelectric electric field, which also
increases the effective carrier density in the ZnO wire. Thus the bent regions in the ZnO wire
have larger photoresponse sensitivities than the straight regions.
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Figure S3 Schematic diagram shows that the electrons were trapped by the piezoelectric
electric field.
Figure S4 Schematic diagram shows that the trapped electrons were released.
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