I am trying to deposite sol gel ZnO thin film on conducting substrate by using chemical such as Zincactetdihydrate(0.5M), 2methoxyethanol and Monoethanol amine(1:1) with spin coating parameters such as 3000rpm/30s, dried at 150 degree for ten times and annealing at 400 degree Celsiuss and then tried to do IV study of my film but always it shows very high current( may be due to prosity ) approximately in the milli to higher order current which is not possible for the film may be it is because of the substrate itself is it always the case with solgel derived film because I have tried a number of time but results remains as it is.
Usually the porosity has a converse effect on the carriers transport and so on the current. Thus your assumption doesn't seem to be correct. It would be helpful if you describe your measurement setup and the quality of size-up the current. Maybe some contaminants are involved here
First of all thanks for replying Sir,
Actually, porosity means that when I make contacts for IV measurements one on the substrate and other on the the surface of the film then there is short through the film that will give the IV characteristic of my substrate only not the film.
Hello Neharana,
How are you making your I-V measurements? From your porosity argument it appears that your contacts are only on the ZnO film, that is, it is a four-point probe or van der Pauw-type measurement.
In that case, I would suggest a vertical measurement where one of the contact should be made to the ZnO film and the other contact is to the substrate. What do you think is the thickness of your ZnO film?
I have also measured through vertical measurement actually as for as the thickness is concerned it should be approximately 500 nm range for 10 times coating if i follow the literature( i dont have facility to measure the thickness). But if it is porous then it will consider zero thickness for the film then IV will give the resistance of the substrate only.
Do you have any other experimental result(s) in support of your porosity hypothesis? It might also be the case that your ZnO film has high concentrations of impurities, or in a worse scenario, the ZnO film is not stoichiometrically ZnO. The point is: have you eliminated other possibilities?
Also, it is not entirely correct that porosity in a 500 nm ZnO film would lead to an electrical 'dead short'. It depends on how you are making contacts to the sample. In fact, it is also possible to make a puncturing contact to a perfectly good (non-porous) film and get what you are getting. You need to give details of your experiment in order to receive scientifically useful suggestions in this forum.
Thank you very much sir,
I have done XRD of my film its fine and other thing that you are saying about the contact I have also tried for different contact and also by using different wires( Al,Cu) but this does not make any change with the high value of current and also I have done the IV of my substrate only which has slope very much near to the slope of of IV through the film
The procedure that I have followed is attached with, this is the method for the synthesis for the sol that I have followed in addition to that I have used used ITO coated glass as a substrate (washed with acetone, methanol, and DI water)
Dear Neharana,
In my opinion since you are using ITO substrate (which is conducting) there is a possibility of shorting when you are making contact on your ZnO film. I guess you might be attaching Cu/Al wires using silver paste. So there is a possibility of silver paste diffusing through your film to ITO giving high current (short). In your case you can either use a patterned ITO or an insulating substrate for IV measurements. If you use an insulating substrate you will have to make in-plane measurements rather than out of plane as for ITO . Moreover do check out the post heating at 600 deg which is quite high in comparison to the glass transition temperature of ur ITO coated glass substrate.......Does ur XRD pattern is indexed to ZnO or it contains some extra peaks.......there must be some ITO peaks.....
Thanks Vishal for your reply
yes there are ITO peaks in addition to the ZnO peaks, and also I have used silver paste for contact yes i also agree that it may lead to short in IV measurements but this is the only option for IV measurements and if this Ag paste is causing problem then this will not make any difference whether i making contact in plane or out of plane so what is the solution for it
Dear Neharana,
As pointed out earlier then either you can pattern your ITO prior to use or switch to an insulating substrate. Hope any of these won't affect your desired application........
Hello Neharana:
I have recently read your query. Possibly it is too late for an answer but, anyway, you may find useful some comets:
I made deposit of ZnO as seed layer on glass substrates with ITO in order to grow nanowires and the colleague with whom I collaborate told me that he checked that the ITO diffused contaminating the sample. Then he began to use FTO, also conductive, if it is a requirement for you.
Regarding the synthesis, I think if you used a temperature higher drying at 170 °C (boiling point of monoethanolamine) instead of 150 ° C possibly would get denser and thicker films. I made ZnO films with diethanolamine (Te = 271 °C) dried at 200 °C and have had problems with not adhesion of the material. The films do not grow by more layers you add.
And I have also made measurements of conductivity in ZnO films, but deposited on SiO2 substrates.
If you are interested, I could recommend same papers or talk more about it.
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