I pattened Silver by E beam lithography followed by e beam deposition and lift off. Over a period of two days, they seem to be developing deposits on the surface. My substrate does come in contact with water during a subsequent fabrication step (if this is pertinent). I keep my sample in a Nitrogen atmosphere.
Dear Saurabh,
if Ag is kept in nitrogen atmosphere nothing happens. We store our Ag-nanowires in distilled water for a long time. Don't store the wires in air. Silver reacts strongly with sulfur (SO2).
I remember that prepared silver nanowires dissolved whereas a period of 2 weeks in air. This must be avoided. nitrogen is inert and a good choice.
With Regard
R. Mitdank
Thanks for the reply Rüdiger,
I have been storing the samples in Nitrogen. The only time they are not in Nitrogen is when I am doing further processing steps (photolithography, BOE etch, etc).
I still get deposit formation. I think I will explore the possibility of capping the Ag with a thin (5 nm layer) of Ti. I already use Ti as an adhesion layer.
I have attached an SEM image for reference. Ag electrodes are fabricated by E beam lithography.
Dear Saurabh Pandey I agree Rüdiger Mitdank , nothing should happen to silver in N2, so these deposits could be formed when your sample is in contact with water. It would be useful to know what is the composition of these deposits, and an EDX ( Energy Dispersive X-Ray) analysis would help a lot. Probably your SEM has this kind of detector installed and it takes just a few minutes.
Looking at the contrast of your image, and the kind of signal (In-Lens), usually the brightest areas correspond to higher atomic numbers, and darked areas to low atomic numbers. (I´m assuming your sample is not metal coated!!). So Ag should be the brightest material on your specimen (Z: Ag=47, Ti=22, Si=14, N=7).
But the deposit is a lot more bright than anyother region, so it should have some component with an atomic number bigger than 47 (Ag), ( I would bet it could be gold (Z Au=79). It could be possible too that the deposit was some kind of insulator (may be some residue of the photoresist, dust, salts, oxides... ) that in general should be darker, but it could accumulate charge on its surface and appear bright, however, chargue distortions are not visible on your image, so I think it could be a metal with a high atomic number like gold.
As previously mentioned, an EDX would help you a lot to know the composition and therefore to assess which is its origin.
Hope it helps!
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