Hello,
I am looking to do TOF-SIMS and XPS experiments on TiO2 and MgF2 crystal surfaces. These experiments require ultra-cleaning methods that will create extremely clean surfaces. My colleague recommends RCA, but I would like to hear other ideas as well.
People in optics recommend cleaning MgF2 with some solvents, but that method definitely won't be clean enough.
TiO2 can be cleaned with Ar+ ion bombardment, but I don't have the equipment for that.
Thank you for your answers, and I would especially appreciate it if you could also provide a reference.
The first cleaning steps depend on the nature of the contaminats and they are straight forward and you have various options: solvent treatment, (nonionic!) detergent solution eventually combined with ultrasound, piranha solution...
For the last flush use a solvent grade with a low content of nonvolatile substances e.g. isopropanol. Let the solvent run off rather than drying it on the surface.
Finally, you will have to remove the layer of adsorbed substances from the high surface free energy surfaces of TiO2 and MgF2. Since the adsorbate layer forms quickly upon exposure to atmosphere you will have to do this in the high vacuum of your analytical instrument immediately before your measurements. I am pretty sure that there is an ion gun at your XPS instrument.
Any in-situ method, especially heating would be good to desorb surface species as well as maintain stoichiometry of the crystals. For argon sputtering I would recommend argon cluster cleaning rather than harder argon ions if it is just surface contamination
Alternatively I would recommend just prior to insertion in to the vacuum chamber, using a "Snow Jet" which is high pressure CO2 and effectively removes the surface organic residue.
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