I am doing research on tin and tin oxide nanoparticles using laser ablation method. Using Nd:YAG laser in visible range (532nm) .By increasing the energy i have observed the decrease in the ratio of number of oxides. What might be the reason?The sample exposure time is constant/
Hi Tanzeeha Jafari,
I think the increase in oxides ratio cause by the oxidation process that occurs at high temperature. By increasing laser energy, the laser discharges more energy in each ablation thus heating the nanoparticles more. I think this concept is same as annealing process.
@Hafzan Ishak: But Tanzeeha Jafari describes a DEcrease in the ratio of oxides.
@Tanzeeha Jafari: In order to answer your question in a better way, could you tell me how you observed this change of ratio? - Was it via XPS or did you use any other method?
And did you ablate the tin/tin oxide with the laser or did you use the laser ablation to deposit tin/tin oxide onto another substrate?
If I understand you correctly, as you increase laser power, the proportion of oxides in the ablation product decreases?
If so, my intuition is that there is insufficient oxygen present for the reaction. Reaction volume - and therefore amount of available oxygen - is roughly constant with laser power. The number of ablation events (or reaction) does increase with laser power, however.
If your current setup performs ablation in room atmosphere, could you perhaps blow pure oxygen at the ablation site?
Hi,
it's Johannes, actually (or Hannes, for short) ;)
I guess, what you have here is a transition of SnO2 into SnO and metallic Sn, which is also corrobortated by your measured values. If you are working in a non-oxidising atmosphere (for example using Ar as a inert gas) and reach high temperatures (which you will in the spot of the laser beam - especially for higher input power) the SnO2 will evaporate and decompose into SnO and an O atom. When the SnO (and maybe even a bit of metallic Sn) gets redeposited onto your surface you will measure values like yours.
What you can do to check that is:
1) try to get somehow a depth profile of your sample - for example with XPS sputtering and (if you can do that):
2) measure the substrate temperature as good as possible to see how high the temperature actually gets (if it is around the evaporation temperature of SnO2, you can be quite sure about the underlying mechanism.
Oxidation increases as the free energy for oxide formation reduces with increase in temperature, i.e., laser energy input. This happens via diffusion of oxygen into the hot material. This can be easily avoided/controlled by simple glass box supplied with inert gas.
@ Xxx Sedao : No, gas shielding alone won't do you any good with this problem as I explained earlier. The oxygen comes form the dissociation of SnO2 at high temperatures, so you create the oxygen by yourself. Hence, there will be oxygen around even if you work in an inert atmosphere.
Thanks for your comments Johannes. I didn't read the full story carefully in the first place - my apologies!
So aye, in depth analysis would be helpful, as XPS + sputtering, or FIB cross-section + EDX mapping for a better comprehension of the distribution of the individual components in question.
Also curious to know what the composition like of the nanoparticles produced from the process
Similar oxygen deficiency has been observed in the glasses after gamma or high energy particle irradiation also, as all the glasses are the product of some oxide mixtures. Such observations are possible only due to evolution of oxygen from the samples or due to diffusion of elements from surface to the bulk or from bulk to the surface during or after irradiation. This effect produces oxygen vacancy (defects) in the samples. You can see
J. Non Crystalline Solids 357 3757 (2011)
J. Synchrotron Radiation 23 1424 (2016)
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