I want to characterize my Graphene on Atomic force Microscopy (AFM), therefore I request you to kindly guide me the sample preparation steps for AFM and cleaning of silicon wafer as a substrate after cutting.
I am thankful to you.
The surface of Si cannot have only Si atoms if exposed to air, as it must be for AFM measurements. It will have a mixture of SiOx and Si(OH)x where x is variable. The process of 'cleaning' basically gets rid of any other material, especially organic, from the surface. A good and consistent way to do this is to oxidize these contaminants with hot solutions of H_2O_2 or chromic acid overnight, followed by rinsing off the oxidized residues with de-ionized water. Hydrocarbons are immune to this oxidation and should be washed away by acetone or toluene. If the acetone wash is carried out before the oxidation and water rinse, we end up with a hydrophilized surface which can be further hydrophilized by soaking in 0.1N NaOH. On the other hand if we end with the acetone wash we get a hydrophobic surface. I guess anything with a biological membrane would attach better to a hydrophilic surface.
Use ultrasonic bath. dip sample in acetone (Use small beaker) put this beaker along sample in ultrasonic bath. set temperature for approx. 50 degree and run upto 15 minutes.
hope it would be helpful
Better use RCA cleaning process that is the golden standard in microelectronic industries.You need to have KOH to remove grease...... then washing with water followed by isopropyl alcohol treatment for drying. We normally avoid acetone
RCA cleaning process. Here instruction http://www.inrf.uci.edu/wordpress/wp-content/uploads/sop-wet-silicon-rca-1.pdf
I agree that RCA cleaning is the standard procedure but please be aware that it leaves a 2 nm thick SiO_x (of uncertain stoichiometry) on the top of the wafer making it hydrophilic. Similarly for HF cleaning there is a SiH/SiF overlayer that is hydrophobic. If you want a really clean surface you have to sputter it with Ar-ions but then you cannot do anything with it outside ultra high vacuum!
We follow a standard and well calibrated sample cleaning procedure at NPL. The protocol is, rinse the silicon substrate with Ethanol and water, repeat it twice, blow dry with compressed argon, UV-Ozone clean it for 10min, following by rinsing with Ethanol and water and blow drying it afterwards using argon. Finally store it is an air tight sample holder.
As mentioned previously, a thin layer of oxide is formed due to exposure to Ozone and rinsing with ethanol removes most of it. We have checked this using XPS with and without rinsing UV-Ozone cleaned wafers.
About the 'RCA cleaning process' suggested above by Joydeep Dutta and others, you can find it explained at a paper written by Werner Kern ('the man himself') at: http://www.microtechprocess.com/pdf/MTS_RCA.pdf
As a viable alternative you may consider also NH4OH aqueous solution (
I also try to obtain atomically clean surface of Si/SiO2 using reactive ıon etching process by oxygen and argon atmosphere together maybe it helps...
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