I have fabricated a sample with structure of FTO/ZnO. FTO and ZnO are the transparent conductive layer and n-type semiconductor, respectively. Subsequently, a DI water droplet was dropped on the ZnO layer and probed using a keithley sourcemeter. The electrical connection is similar to a typical water-gate FET configuration.
Upon UV illumination with no applied bias, photocurrent was generated from the sample. My question are as followed:
What is the role of the DI water droplet in water-gate FET? Is the water acting as a transport medium for the charges or there's an electrochemical reaction happening between ZnO and water which resulted in the photocurrent.
Hi Fang Sheng,
Have a look at this article: Article A Water-Gate Organic Field-Effect Transistor
.It will answer all your questions...
L.A. Majewski
Hi,
You can also check https://ris.utwente.nl/ws/files/6501237/Bergveld03thirty.pdf and reference number [8].
Regards,
MK
Hi Lim,
Based on your limited information, I guess the DI water simply acts as a gate. I assumed your structures are in stacks of 2D, using DI water it simply covers wider area of the ZnO. The second guess is because you need to perform photocurrent experimental, the gate should be transparent, and water is a simple choice as well as long as well distributed on the ZnO.
I don't think the electrochemical plays a significant role here in your experimental setup for photocurrent effect, because ZnO solely has photocurrent phenomena in UV-VIS excitation.
My further hypothesis (need more literature study) is:
DI water is a semiconductor (ultrapure water is an insulator material).
One study stated that the fermi level of H2O is nearly above the valence band (like a p-type) see DOI: 10.1039/C4CP04202F. If this assumption is accurate...
Therefore, here you simply have a PN junction from the DI water and ZnO. Therefore the UV-VIS excitation induced electron transition in the DI water (P-type), and the electron flows to the ZnO (n-type), and to the FTO as the conductor during your measurement.
Good luck with your research.
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