I recently compared how different gasses influence crystallisation of thin film. I used Nitrogen, Carbon dioxide (CO2), Argon, Ambient air. And got easy crystalization of Zinc, Iron and Nickle thin film in comparison with thin film prepared in other gasses.
My colleague told me that maybe polarity of nitrogen in my reaction is changed so it become more polar and maybe that is a reason of crystallisation.
I do not anneal the sample and during preparation I use high voltage discharge.
Why this happens only with nitrogen and not other gasses?
It is possible you are generating nitrides which form spontaneously when sputtering many metals in a nitrogen atmosphere. ( Though you have not shared your production process so I don't know how you are preparing your films. )
Nitrogen incorporation enhances crystallisation formation and results in increases in properties such as elastic moduli, microhardness, glass transition and softening temperatures, viscosity, glass density and fractional compactness because of extra cross linkages in the glass network.
In general, nitrogen increases the stability of oxynitride film. The conventional process to produce a film-ceramic involves two steps: a lower temperature heat treatment of film, generally just above the film transition temperature, to induce nucleation followed by heating to a second higher temperature, the so-called crystallisation temperature, to allow growth of the pre-formed nuclei. The crystalline phases formed depend on both the composition of the parent film and the heat-treatment process but in many cases, oxide phases form first leaving the residual film more N-rich.
SR,
The question you asked is not sufficiently informative. e.g. What are you synthesizing, pure metals or oxides or nitrites? How do you synthesize, is it vapor transport method or sputtering or laser deposition, etc.? If you could provide such information, possibly this discussion will be channeled well. Since various synthesis techniques operates at various pressures, the response of same gas at various pressure has to be different.
Best.
Ranjit A. Patil thank you very much, I am using pure metals, in form of metal wires and ionize them with Sparking discharge process, which is basically just applied high voltage at the end of the wire tips which melt metal wire while creating nanoparticles via aerosol vapor transport. I spark metal wire inside of chamber in which I flow the gasses with speed of 10 l per second. Only when pure nitrogen is flowed crystalization is achieved.
Robert Mahar yes you are complitly correct, when I checked with XPS there are nitrides with samples prepared in nitrogen but there are also carbonates with samples prepared in CO2, so now is the question, why there is no crystallization of carbonates? also nitrogen content in thin film is very small, less than 0.5%
Rakesh Sonker thank you very much, very interesting information. In your opinion why CO2 or carbonates formation didnt crystallized as well as samples prepared in Nitrogen?
SR, Thanks for the more details on the experiment. In my opinion, as I understand your synthesis technique, the answer of your question is highly related to 'dissociation energy' of molecules. Since you apply a high voltage to evaporate the source metal, in that hot region these gases may dissociate and turns in to plasma. Since the dissociation energy of the CO2 is high than the N2 at constant temp., N2 may provide highly active plasma environment than CO2. In case of Ar it may require a very high voltage to have plasma state. Another gas O2 (you didn't mentioned here but it has even lower dissociation energy than N2) may offer even better crystallization but thin films would be of metal oxide. In the active the plasma environment, metal vapors would get longer time to settle and form a crystal. The slower crystallization processes, the higher the crystallinity.
Plasma form in the presence of Argon, Nitrogen gas can be generate at similar condition ( in our case we have used RF frequency 133 kHz and 1.2kVp-p). Our experimental conditions are not for the NP formation its just for ionization of polystyrene for Mass Spectrometry purpose.
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