Dust particles settles easily on clean surfaces because of static charges collection if it is a dielectric surface. The most effective way is to blow dry nitrogen from an air-ionizing gun. The nitrogen passes through a high voltage probe and ionized nitrogen helps to unsettle the dust particles and removes because of the jet force. The jet should be as tangential as possible.

Are you sure that the particles really are dust from air? They might have been on the substrate before growth, they may form during growth (precipitates), they may come from somewhere inside the chamber, they may form during washing due to a chemical reaction or adhesion of particles in the liquid, they may even form due to a chemical reaction with moist air. Depends on the material system and deposition method.

Rubbing with a cotton swab inside some solvent (water, acetone, alcohol, ...) is more effective in removing particles than ultrasonication, but is only advisable for hard films. If rubbing does not remove the particles, they are most likely not dust from air.

If you really want clean samples, there is no way around a cleanroom!

Thank Weber very much! Yes, you are right there are other possibility to pollute the sample such as you have mentioned. the pollutions caused by some of them can not be cleaned, and some can be cleaned. For us, we think the dust pollution is the most possible because we can decrease the density of the particles to a certain extent by washing, but that is not enough.

Hi,

Immediate after film deposition, if you want to remove loosely adherent particles, you may used solution of acetic acid in low % or methanol with distilled water for washing in an ultrasonically. It's also worked well to remove dust or other particles from already deposited films.

See ref... J appl Phys 111, 113510 (2012).

Hi,

Immediate after film deposition, you can use a hydrogen plasma

If it is dust particle, it is just sitting there. Even blowing may help. If the film is not too soft, a camel hair brush can also be tried ( the one used to clean lens with coatings)

Cleaning is one of the more difficult task to perform. But: what are you going ti do on this film? The kind of "cleaning" depends on this. For instance, ig you want to perform epitaxial growth, the only way to do that is an in-situ treatment. Even a "clean" film, i.e. without particulates on it becomes very quickly covered by a thin film of oxide. Or, in case of oxide film, the open bonds used by the arriving adatoms to continue the growth will close on thirselves, preventing the adhesion of further layers, wich will be bonded only by Van der Waals forces.

Hi,

If you are looking at having a surface which is free of particles (size of the order of few 100 nm or less), the only way is to do the entire process in a clean room. The reason is that in normal air, there will be millions of particles of that size. Some of this will anyway get attached to the surface of anything due to electrostatic forces. I think that irrespective of what cleaning procedure you use, the surface will inevitably get covered many of these particles, unless the entire process and all experiments or studies are done in a clean room.

THere could be some alternatives for the problem. But these will depend on what you want to do with the film deposited. For example, you could try to passivate the surface of the film. This is referred to as capping the film by another protective layer of a non-reactive material such as gold. But the particles will still stick to the surface of the capping layer. But if any properties of your film are getting modified by the particles, it might be different in this case.

Another alternative could be to modify your experimental studies such that you could always keep the film/substrate in a protective medium such as a liquid or in vacuum.

Many cases, we want to iamge the surface morphology of the sample by AFM, if the dust particle is too many, the image would be terrible bad. Samely. just as the statement by Giuseppe Queirolo, the surface clean is very important for a epitaxial growth. However, we have no clean room and not to mention a in situ equipment, so we want to pursue a method which could clean to decrease the dust particles as a pre-step of the AFM or eptaxial growth. allways we first ultrasonicly wash the sample by acetone and alchole , and then blow with pressed gas. But the efficiency is not quite good.

If you are sure that you don't have those particle during deposition process (as that depends on equipment that you use, chamber conditions etc) then I would recommend to put your sample in some clean box or wafer carrier box immediately after deposition and then just expose your sample only at AFM facilities. Cheers, Andrew

Keep samples in vacuum desiccator

Perform all the processes in a laminar flood hood would help in creating a small clean ambient; it is not a clean room, but it is much less expensive. And take care when blowing gas: it can literaly bury the particle in your substrate, or even add powder if not sufficiently filtered.

Thank Giuseppe very much. You have said is quite right! Some times , we found blowing did not clean the film, inversely add dust on it

Clean glassware, suitable wipes, clean blowing gas, clean chemicals, clean ambient can only be found in a proper cleanroom. If you have high demands on your samples, there is really no way around a cleanroom! Everthing else is a compromise.

Dust particles settles easily on clean surfaces because of static charges collection if it is a dielectric surface. The most effective way is to blow dry nitrogen from an air-ionizing gun. The nitrogen passes through a high voltage probe and ionized nitrogen helps to unsettle the dust particles and removes because of the jet force. The jet should be as tangential as possible.

You can do the cleaning process in a Clean room and transfer it into a vacuum desiccator, which can be opened just before your AFM measurement.

Keep the sample face down all the time -- i) clip the sample horizontally face down and sonicate while rocking (manually) the sample gently, ii) if you do not have a ionizing gun, use a 0.01 micron (or smaller) filter paper, rub it onto a fine polishing cloth (not a sand paper) and stick it to your compressed air gun (rubbed side facing in), iii) blow air tangentially keeping the sample horizontal and face down. Use the sample fresh, don't store. Hope this helps!

For cleaning film surfaces in vacuum you also can try to use the beam of low energy Ar plasma. But the cleaning should be done immediately before AFM study or maybe even "in situ".

One of simple possibilities is to use "First contact".

http://shop.stanwaxlaser.co.uk/first-contact-polymer-optics-cleaner---opticlean-1-p.asp

It is a polymer disolved in the organic solvent and after pealing out from the surface it can remove even nanoparticles as I found in the experiment.

Have a nice day.