Hello,

I think that the reason of of formation of empty-space-regions after your 1st doctor-blading - is caused by impurities on substrate (like fatty/oily regions - where the wettability is reduced). That's why even if you try to "cure" the defects by 2nd run of doctor blade - there will be no success. [even if abter 2nd doct.-blading you will be able to fill the defective places - the structure at the boundaries formed between 1st layer and filled layer - will for sure be different. [of course the same (of impurities) problem can occure on the doctor-blade-itself...   Regards,     Leonid

Leonid V Vladimirov Dear Sir, Thank You for your answer.

I might use dish soap with strong grease cutting power? It sounds inadvisable to pour the soap directly  onto the substrate  which means the soap should be mixed with the water. because I poured the soap onto the FTO.

It sounds inadvisable to pour the soap directly  onto the substrate which means the soap should be mixed with the water. 

I also have problems:

1. I also get many bubbles which is strange because everything look fine at first and then bubbles started forming beneath it. Does this happen for the same reason above or because I covered the substrate with a small lid? Its shown as the picture attached.

2. and theres always dust  whether i cover it or not during calcining. Is there anyway to rid of the dusts? Sometimes the film comes out fine but destroyed with speckles of dust on or inside it despite washing the FTO for an hour.

Hello,

1. I do not know what means abbreviation "FTO"

2. I would NOT use soap for removing impurities from the surface

3. if "FTO" is a solid surface (like for example glass - I would try to consequently use

several simple solvents - to clean the surface from greesy/oily impurities

Namely: aceton, then toluene or any other aromatics, after that - rinse by distilled water; and in order to completely remove the traces of water - place your substrate in heating oven for 130C for 25 minutes. - IT IS a STANDARD surface-cleaning procedure.

Regards,       Leonid

P.S. in order to remove the dust - the best I think is ethanol; so wash in ethanol after toluene.

Hello Sir,

1. FTO( Flourine doped tin oxide)is a piece of glass such as the attached picture above. It has a conductive side of doped or deposited Tin oxide layer with 8 ohm/cm2 of a few nm thick to allow deposition of thin film such as TiO2 of it. Usually people will deposit on either thin piece of glass or conductive side of FTO, on the other side of it is a normal glass side. It is a bit thicker than normal glass (~2mm). It is washed with the conductive layer facing up.  

2. Thanks for the tip. I usually wash it using 30 min of soap and deionised water, 15 min of deiionised water and 15 min of ethanol then heat at 450C for 15 min and 15 min at 500C. 

3.But i will try the standard procedure mentioned. 

Regards

Adrian