I found that due to improper cleaning of substrate, my AFM images are not of good quality. Earlier, I had cleaned the substrates only by sonication in acetone, but that is not sufficient.
It depends on how smooth you want the surface to be, but some combination of gas plasma and/or chemical 'etch' would get rid of any organic residues on the surface. For example, treating silicon wafers with piranha solution is a (brutal) method for getting rid of surface contaminants. Gas plasma is easier, however. The ideal method will really depend on what you want to use the surfaces for and what kind of contamination is on the substrate.
The best clean and smooth surface for AFM sample preparation is a fresh cleavage of mica or pyrolytic graphite. The preparation is very simple: stick a small plate of mica or graphite to substrate by bilateral adhesive tape and stick adhesive tape above, detach it and you will have ideal smooth and clean surface. It is a classical method of surface preparation.
Souvik Ata, are you sure that a cause of low AFM-images quality is a contamination of a substrate? It is untypical. You can exclude this factor by using a fresh cleavage. There are some typical factors those influence the AFM images quality:
- tip-sample interaction (indentation to very soft samples, stick etc.);
- vibrations and acustic noise;
- incorrect AFM parameters: very high or very low magnitude of oscillations in taping mode, very high loading in contact mode etc;
- contamination or degradation of AFM probe's tip;
- meniscus forces by contact between a tip and a wet sample;
- very high or very low scanning rate;
- failure of the AFM;
Check all these factors and may the Force be with you! :)
Good luck!
As basic cleaning for SiOx and glass slides we have good experience with subsequent sonication in chloroform, ethanol or isopropanol and finally DI water, then blow dry with nitrogen. We use plasma cleaning only if needed for rendering the surface hydrophilic and in some cases piranha cleaning.
For mica, I would rather not "clean" the surface at all, but always use freshly cleaved pieces as described by colleagues above.
What type of "low quality" let's you think that you have a problem with your surfaces? Is it particles in your image or something else?
According to just 'have clean surface' of mica or/and HOPG - simply stick adhesive tape and then remove with a dirty layer. According to clean samples or/and surface I using LADD replicating tape - it takes out all dust and other contaminants. Beware to use it for some polymer not resistant for acetone.
I am also not convinced that the cleanliness of the substrate is the reason why your AFM images are of poor quality, however in case you have a problem with organic contaminants then the mentioned plasma cleaning approach should work well (or piranha solution, if you feel up to it). However for the purposes of applications it is important to recognize that both these processes give arise hydrophilic surface character for glass or silicon.
If you on the other hand have problems with inorganic particulate contamination, there may not be a perfect easy-to-implement solution. Aside from the numerous good suggestions presented here, I have had good experience of using intense jets of cold, inert gas (such as laser-CO2) directed onto the sample at a moderate (~ 45 deg.) angle of attack. But for this you need far higher pressures than your average laboratory nitrogen pistol. If the particles are not very small, gentle rubbing with cotton sticks in warm solvent (e.g. acetone) may also be beneficial however you should be aware of the possibility of scratching the surface.
We do Piranha cleaning followed by 1 min dipping in 10% HF solution for Silicon wafer cleaning.
If you do sonication in acetone only it will be problematic. There might be some contamination from acetone. you should make sonication in alcohol (IPA)after in acetone. Then make sonication in DI water. After drying you can use. With that procedure, I have obtained relailable images with no error in image
Cleave the mica using double-sided tape. Mica is composed of layers of minerals separated by intercalating ions, each layer can be peeled off when adhered to double-sided tape.
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