based on aspect ratio controlled ZnO nanorods Teahoon Park - - PowerPoint PPT Presentation

Highly sensitive wireless UV sensor platform based on aspect ratio controlled ZnO nanorods

Teahoon Park

thpark@kims.re.kr

To synthesize ZnO nanorods by solution-processing method with controlling the length of them to understand the affects of the length of ZnO nanorods on ZnO nanorods based UV sensors.

• Oxygen molecules are adsorbed onto ZnO

surfaces by capturing free electrons which creates a low-conductivity depletion layer

• Upon UV illumination, hole discharge the

negatively charged adsorbed oxygen ions to photodesorb oxygen from the surfaces or effectively get trapped at the ZnO surfaces, resulting in an increase in the free carrier concentration

200 400 600 800 1000 10

• 11

10

• 10

10

• 9

10

• 8

10

• 7

10

• 6

Current (A) Time (sec)

0.5M 1 M 2 M 3 M

High h aspect spect ratio io Solut ution ion proces

• cessable

sable Fast st & h high h sens ensitiv itivity ty Wire reless less UV s sens ensor r plat atform

• rm

ZnO nanost nostru ructure cture

58.5 5 times

High concentration Different concentration Zinc precursor Base material Low concentration

Seeding Step Growth Step

TEM and XRD pattern of ZnO nanomaterials with different aspect ratio

200 400 600 800 1000 10-11 10-10 10-9 10-8 10-7 10-6

Current (A) Time (sec)

0.5M 1 M 2 M 3 M

• 30
• 20
• 10

10 20 30

• 2.0x10-6
• 1.5x10-6
• 1.0x10-6
• 5.0x10-7

0.0 5.0x10-7 1.0x10-6 1.5x10-6 2.0x10-6

Current (A) Voltage (V)

0.5M 1 M 2 M 3 M

200 400 600 800 1000

840W/cm2 665W/cm2 368W/cm2 253W/cm2 162W/cm2

Current (a.u.) Time (sec)

200 400 600 800 1000 0.0 1.0x10

• 6

2.0x10

• 6

3.0x10

• 6

4.0x10

• 6

Experiment data Linear fit (R

2=0.99)

Response Current (A) UV intensity (W/cm

2)

Optoelectric properties of ZnO NRs under repeated UV irradiation on and off

UV On UV Off UV On

ZnO NR

A schematic diagram of the circuitry Photographic images of the Bluetooth connected ZnO NRs UV sensor module

• Aspect ratio controlled ZnO nanorods were successfully synthesized via two step

processes.

• The ZnO NR morphology and crystal structure were analyzed. The original wurtzite

structure of ZnO was observed.

• As the length of ZnO nanorods was longer, UV responsivity is 58.5 times higher.
• The wireless ZnO NR UV sensor platform was operated successfully and the sensing

results were observed on a smartphone screen connected through Bluetooth.

Conclusion Future work

• Fiber type or flexible sensors with high sensitivity based on metal oxide materials.
• Composites sensor will be prepared for wearable devices.