Look at the oxidation states in relation to the 285 eV carbon 1s peak (some debate about this value). In air or in the presence of O, I would expect the Au to be in the +3 oxidation state.

I think I might be confusing in mu question. I need to make sure the Sulfur is bound to gold dots, not Silicon

Metal sulfide~161.5 Thiol bound to gold, Au-S 162.5, there is the bonding of Au with S. however you also have contamination with sulfate. Can you share method of preparation and other peaks?

Thanks Stefan,

I prepared the gold dot pattern on a silicon wafer via Interferometric lithography. The gold has been deposited with vacuum evaporation

Then, I immersed the chips in NaBH4 (0.5 mM) for 10 min. to remove the SAMs that might have left from last time. ( Article A Method for Removing Self-Assembled Monolayers on Gold

Then wash them with pure Ethanol and dry with N2, clean them under UV Ozone for 1 hour. Immerse them in 1mM ( Alkanethoil (90% final concentration 1mM) and Biotinylated thiols (10%) for 18 hours). afterward, sonicate the samples in clean ethanol for 1 min and wash them 3 times and dry with N2. I try to keep them in a container filled by N2. but it can not be done perfectly and the samples still might have air contact. The XPS was done in 2 hours after finishing the preparation. you can look at the results in the file attached

Please let me know what you think.

thanks

yes, you have contamination with Sodium, contamination with F!!! How it gets there, and really strong Oxygen peak. take a look at O 1s peak and if you found 531.2 eV or aroud 530 eV you have also contamination with Gold oxide. However you dont have Sulphur peak!!! this is strange or maybe is very weak. can you zoom in between 164-172 eV. Akram Etemadi

Yes you are right. I do not know how F is there. I have a high resolution for Sulfur (attached). I will take a look at O 1s but I do not know how Gold oxide contamination could happen.

yes. for sure you have sulfide Akram Etemadi and thiol, but very low concentration comparing to other compounds.

Thanks Stefan for your comments. Do you know how I can aboid Gold oxide contamination or other contamination? I cleaned the chips verry efficiently with UB ozone. But still have them

By the way, F 1s is because of HF etch for cleaning the Si wafer at the first step

So your cleaning is actually a source of contamination? You need to change the method of synthesis Au Sulfide. I assume you want to use it for biosensors application or what?