Environmental Engineering Reference
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to each other at the bottom and single crystalline nature of nanowire give
highly ei cient charge transport through the bottom of the nanowire,
called the conducting channel.
16.5.1
Electrical Conductivity of Nanowire Film in Dark
We have recently shown that defects can signii cantly change electrical con-
ductivity of ZnO nanowire i lms [25, 46, 48, 158]. h e ef ect on electrical
conductivity is probed by comparing just three post-growth treated ZnO
nanowire i lms with variable concentrations of defects. Figure 16.6a illus-
trates the dark- and photocurrent measurements of as-grown, air annealed
(400
C) nanowire i lms. h e dark conductiv-
ity of NWs array is found to increase at er annealing in air and oxygen ambi-
ance. Relatively less value of dark conductance of as-grown array is primarily
observed due to the presence of surface defects/amorphous layer (Zn(OH) 2 )
°
C), and oxygen annealed (400
°
10 -3
I G /I UV = 1.7
I G /I UV = 1.8
ASG
10 -4
ASG
Air_AN
O2_AN
I γ
I G
PHOTO
10 -5
I UV
10 -6
I R
( c )
10 -7
ASG
Air_AN
O2_AN
I G /I UV = 0.85
I γ /I UV = 0.86
Air_Annealed
DARK
I UV
10 -8
-4
3 2 101234
( a )
I R
I
I G
Voltage (V)
γ
ASG
Air_AN
O2_AN
( d )
I G /I UV = 0.38
I
Oxygen_Annealed
/I UV = 0.65
γ
I γ
I R
I G
360
450 540
Wavelength (nm)
630
720
810
400
500
600
700
800
( b )
( e )
Wavelength (nm)
Figure 16.6 (a) Dark- and photocurrent measurement and (b) room temperature PL
measurements of as-grown, air annealed (400
C) ZnO
nanowire array. h ree-peak Gaussian i tting for I G (green defect), I Y (yellow defect), and
I R  (Red defect) in PL spectrum (c) as-grown, (d) air annealed, and (e) oxygen annealed
ZnO NWs [25].
°
C) and oxygen annealed (400
°
 
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