During preparation of Sb2Se3 thin films, the annealing process is generaly done in a tubular furnace under N2 and Se powder at 350 °C. But there is always the presence of Sb2O3, so I am wondering if there is a possibility of oxygen diffusion from the glass substrate into the deposit.
Thank you
Khadija Abouabassi it is impossible especially at this temperature range (350C).
But the presence of Sb2O3 is not surprising. This oxygen is coming from the air molecules already present inside the tubular furnace. It is essential to complete evacuate the air from the tubular furnace before heating. You can use a vacuum pump to do so, infact keep the pump vacuuming for a considerable time (use a vacuum guage to ensure the proper vacuum conditions inside the furnace).
Another way is to keep your samples inside a sealed glass quartz. That will also need a vacuum pump but it will be quicker and small vacuum pump may do the needful. (Howeverm you will have to learn the quartz sealing technique).
Best Wishes
Dear Khadija Abouabassi,
The question is related to possibility of oxygen diffusion from the glass substrate at the temperature (350C). Actually, the glass degassing temperature may be responsible due to the quality of glass substrate. The substrate may be carefully chosen based on glass melting temperature and which should be above 600 C, so that with the processing temperature there is no scope of oxygen diffusion from the substrate. The ambient requires to purge with Nitrogen before heating with the processing temperature, such that the oxygen level inside the furnace is minimized.
Thanks
Khadija Abouabassi
I assume your furnace material is quartz (and not soda lime glass) but you do not state this. The oxygen was present in your samples long before they reached the furnace if your materials have been stored in air or in the presence of moisture (or both). Even if you've dealt with this, when you remove your materials from the furnace and store them in air (other than in a vacuum desiccator) then they will pick up oxygen from the atmosphere. XPS/ESCA will show oxide on the surface of any material stored in, or exposed to, air. The elements will be in their higher oxidation states typically and chemisorption-induced segregation will occur in any system with more than 2 components meaning that the bulk and surface (10 - 15 atomic layers) can never be the same.
Only route to prevent this (if the oxide is a show-stopper) is to carry out the preparation in a reducing environment e.g. H2. Then do what you need to use the material for - without exposing it to air or moisture.
Dear Syed Waqar Hasan, Somenath Chatterjee and Alan F Rawle,
Thank you very much for responding to my question,
Your answers clarify a lot concerning my problem,
Effectively Mr. Rawle my furnace material is quartz and also my samples are exposed to moisture (electrodeposition in an aqueous bath) and to air.
As working in a reductive environment e.g. H2 is not available in my lab, I try to make a chemical etching by HCl just before depositing the buffer layer (CdS).
Thank you
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