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Supplementary Information

Large Area Transparent ZnO Photodetectors with Au Wire Network

Electrodes

S. Kiruthika,a Shubra Singhb and Giridhar U. Kulkarnic*†

a Chemistry & Physics of Materials Unit and Thematic Unit of Excellence in Nanochemistry,

Jawaharlal Nehru Centre for Advanced Scientific Research,

Jakkur P.O., Bangalore 560064, India.

b as a Visiting Faculty to JNCASR from Crystal Growth Centre, Anna University, Chennai 600025, India

c Centre for Nano and Soft Matter Sciences, Jalahalli, Bangalore 560013, India.

† On lien from JNCASR Bangalore-560064, India.

*E-mail: guk@cens.res.in

Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2016

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Fig. S1 (a) Schematic depiction of fabrication of Au /ZnO/Au photodetector. (b) and (c) SEM

images of crackle network and Au network fabricated on the glass substrate, respectively. (d)

SEM and (e) optical microscopic image of a complete device clearly showing the presence of

ZnO layer sandwiched between top and bottom Au networks. (f) - (i) represents the elemental

mapping of a device where the presence of Au in network structure and ZnO as a thin film is

evident.

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1 cm

600 1200 1800 2400 30000

20

40

60

80

100Tr

ansm

ittan

ce (%

)

Wavelength (nm)

Au wire network (quartz) Au wire network (glass)

Fig. S2 Transmittance spectrum of Au wire network on a glass substrate (300-1300 nm) and a

quartz substrate (200 to 3000 nm). The inset is the photograph of Au wire network on a quartz

substrate.

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Fig. S3 (a) EDAX spectrum of ZnO layer; Inset shows the SEM image of ZnO film of 100 nm

thickness without the Au network. (b) XRD patterns of ZnO film deposited on glass substrate

exhibits diffraction peaks characteristic to (100) and (110) of ZnO. (c) Optical profiler image of

ZnO thin film deposited over Au wire mesh. Above is the schematic illustration denoted with a

thickness of ZnO.

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400 800 1200 1600 200010

20

30

40

50

60

70

Tran

smitt

ance

(%)

Wavelength (nm)

Au/ ZnO (250 nm)/ Au on quartz

Fig. S4 Transmittance spectrum of the device fabricated on the quartz substrate. The

transmittance spectrum of the device on the quartz substrate clearly indicates that absorption

below 400 nm is mainly due to ZnO layer as metal mesh and quartz is transparent at this

wavelength (see Fig. S2).

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-6 -4 -2 0 2 4 6

-20

-10

0

10

20 UV Dark

Curre

nt (

A)

Voltage (V)

GlassZnO (100 nm)

-4 -2 0 2 4-2

-1

0

1

2

Cur

rent

(mA

)

Voltage (V)

Dark UV

GlassZnO (190 nm)

((I-I0)/ I0)% = 189 ((I-I0)/ I0)% = 33

(a) (b)

Fig. S5 I-V characteristics of (a) 100 and (b) 190 nm ZnO films on a glass substrate with Ag

paint contact. The inset shows the schematic of measurements.

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-6 -4 -2 0 2 4 6-0.4

-0.2

0.0

0.2

0.4 Dark UV

Curre

nt (m

A)

Voltage (V)

-6 -4 -2 0 2 4 6-6-4-20246

Curre

nt (m

A)

Voltage (V)

Dark UV

-6 -4 -2 0 2 4 6

-10

-5

0

5

10 Dark UV

Curre

nt (m

A)

Voltage (V)

-6 -4 -2 0 2 4 6-4

-2

0

2

4 Dark UV

Curre

nt (m

A)

Voltage (V)

(b)(a)

(c) (d)

125 nm 190 nm

220 nm 250 nm

Fig. S6 (a-d) I-V characteristics of Au mesh/ZnO/Au mesh with different ZnO layer thickness.

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30 45 60 75

Inte

nsity

(a.u

.)

(100

)(0

02)

(101

)

(102

) (110

)

(103

)(2

00) (1

12)

(201

)(0

04)

2θ (°)

Fig. S7 XRD pattern of ZnO pellet used as the target for pulsed laser deposition.

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Note S1

The barrier height for Au mesh/ZnO (100 nm)/Au mesh was calculated using following equation.

Barrier height formula and calculation

where,

k Boltzmann constant = 1.3806 x 10-23 J K-1

T Temperature in Kelvin = 298 K

Q The elementary charge = 1.602x10-19 C

A Area of the contact = 0.6 cm2

A* Richardson constant for ZnO= 32 A cm-2 K-2

Is Saturation current = Intercept (lnIs) Is = 129 nA

Thus, Φb = 0.776 eV

The obtained barrier height is comparable to the barrier height of interdigitated configuration of

Au/ZnO/Au (0.8 eV)1 and higher (0.735 eV) than the planar asymmetric electrode configuration

(Au/Cr/ZnO/Al).2

References

1. H. Y. Chen, K- W. Liu, X. Chen, Z- Z. Zhang, M- M. Fan, M- M. Jiang, X- H. Xie, H- F. Zhao and D-

Z. Shen, J. Mater. Chem. C, 2014, 2, 9689-9694.

2. G. M. Ali and P. Chakrabarti, IEEE Photonics J. 2010, 2, 784-793.