Sputtering

Discussion in 'Physics & Math' started by arauca, Mar 20, 2012.

  1. arauca Banned Banned

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    Why sputtering work in a particular pressure range , why not in a vacuum 10-8 micron ? or lover , and why not on atmospheric pressure ?
     
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  3. RealityCheck Banned Banned

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    Hi arauca, pleased to meet you.

    I'm not sure, but I suspect that if the 'nozzle' stream were to exit into vacuum, it would expand rapdly and too much, and most of the 'particles' in the stream would be wasted.

    In a pressure environment, the exit stream would remain more 'coherent' for longer and most/all of it would reach the target surface.

    If you read up on 'Rocket Nozzle' designs for vacuum/atmospheric transit, you would see that atmospheric nozzles need not be as large as the vaccum nozzles because the exhaust stream would not need the extra nozzle 'expansion bell' dimensions which an in-vacuum design requires because there is no atmospheric pressure to 'contain' the exhaust gases for long enough for all/most of the impulse benefit to be obtained from the exhaust system stream constituents/thrust.

    Sorry that's all I can remember at this time. Look up rockets and nozzle designs and you will see what I mean. Gotta go! Cheers!

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  5. prometheus viva voce! Registered Senior Member

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    I think you need to have another go at this question.

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  7. arauca Banned Banned

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    Like what what is that you don't understand ?
     
  8. prometheus viva voce! Registered Senior Member

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    Please restate your question in coherent English.
     
  9. Emil Valued Senior Member

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    If you give an example for sputtering, maybe I'd better understand your question.(It's like fuel injection in the engine from your car?)
     
  10. arauca Banned Banned

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    Do you know what sputtering means ? if not check wiki., Science is science sputtering was developed here thin metallic coating , perhaps you are to young to know when it was developed , but it was developed by physicists in the 50 to 60 . There are two electrode as normal one positive an the other negative , the coating target is in the Vincenty, Normally Argon is used the pressure normally is about 0.2 mm or lower but no lover then 0.0001 mm Hg.
    From memory at 5 mm Hg sparking will set it
    " " 0.0001 no glow is formed therefore at a given distance there is no ionization and so ejection metal from the cathode does not take place . for the object to be coated

    Science language used in the past was German now is English , perhaps in the future is going to be Chinese , so don't jump with your English
     
  11. Emil Valued Senior Member

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    Whoops ... this is beyond my tether.
     
  12. prometheus viva voce! Registered Senior Member

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    Please don't patronise me. The language of science is not relevant - the language of this forum is English, and your ability to type it is clearly lacking.
     
  13. wlminex Banned Banned

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    We commonly use 'sputtering' (electro-atomization) from high-purity carbon electrodes to sputter-coat samples for electron microscopy and electron microprobe analyses. We too utilize an ~ 10^-8 mtorr evacuated bell jar arrangement in which the 'sample' (to be coated) is placed in the vicinity of . . . but not too near . . . one electrode . Such sputtering in higher pressures (less vacuum) produces a 'rougher' (coarser carbon particulates) coating. For good sample surface conductivity, a very fine (angstrom-level) and uniform carbon coating is required. If enough 'air' molecules remain in the evacuated sputter chamber, these molecules nucleate sputtered carbon particulates, forming coatings that are too coarse for uniform surface conductivity. These same issues apply to any vacuum-coating/sputtering (e.g., gold, etc.) process.

    As an added thought . . . . in commercial electrostatic coating processes (e.g., painting and related) these issues are not too important and they usually are completed in a non-vacuum environment
     
    Last edited: Mar 22, 2012
  14. RealityCheck Banned Banned

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    Hi wiminex.

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    I'm curious, if the coating is required to be so uniform, would a vacuum system with electric crucibles which vaporize the material for the coating be more suitable/reliable? The vaporized material 'condenses' quite satisfactorily on any nearby cooler surface. I think this is what is used when making 'aluminized plastic film' in a roll which is fed by 'crucibles' where the aluminium is vaporized and then condenses onto the cool nearby film quite uniformly.

    Are ther any impediments to doing the same with Carbon (ie, does it vaporize or does it 'sublimate' satisgfactorily, or is the crucible temperature required too high to make it feasible?

    Just a thought. G'night.

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  15. origin Heading towards oblivion Valued Senior Member

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    The general answer to your question is that if you sputtered at atmospheric pressure you would add impurities into the sputtered film which would be bad. If you operated at atmospheric pressure with air you would probably oxidize the sputtered atoms which would be bad. The reason that the vacuum is not taken down to an extreme level has several reasons, I suppose. If you have a flow of an inert gas (with the system under vacuum) you can remove the heat generated. The main reason is that the lower the vacuum is not used is that it is not necessary. To get to the lower vacuum the equipment is more difficult to maintain and it is more expensive to produce.

    I work with film deposition - primarily CVD (Chemical Vapor Deposition) - and not sputtering (which is essentially a form of PVD) but I think the overall paramater settings have the same reasons.
     
  16. arauca Banned Banned

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    So you do CVD what do you deposit ? and on what substrate ?
     
  17. kevinalm Registered Senior Member

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    Sputtering is a very old (nearly obsolete) method of depositing thin coatings (on lenses and the like). It has largely been replaced by vapor depositation as origin has described. The optimum pressure is a complex phenomenon. If either too high or too low the voltage nescessary to strike the arc through the vacuum chamber will be too high. Also, of concern are possible contamination or chemical reactions as have been mentioned. In practice, it was likely as much a question of trial and error as anything.
     
  18. arauca Banned Banned

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    "Sputtering is a very old (nearly obsolete) "
    I don't know were did you get your information ? There are plenty if thin film cotters by sputtering and there are plenty of equipment suppliers.
    I do't know what contaminant you are referring . Because contaminant depend on your pumping , how you flush your system and the material source , you preclean your substrate by sputtering on it first .
    Your substrate can be cold . On CVD can be contaminate easier, your environment will depend on the decomposition temperature of the coating temperature , and during the deposition you have some reactant biproduct that will be introduced onto the substrate .
    So I question on how much experience you have , based on your post.
     
  19. origin Heading towards oblivion Valued Senior Member

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    TiCN. Stainless Steel.
     
  20. arauca Banned Banned

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    By the way what us the boiling point and the decomposition temperature of TICN2 or is it TICNFe
     
  21. origin Heading towards oblivion Valued Senior Member

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    The material is a Ti(CN) Titanium carbonitride. It is written Ti(CN) because the C and the N concentrations vary througout the crystals. It is a ceramic crystaline material with very high hardness. I have no idea what the melting or boiling temperature is. Consdering that HT-TiCN crystals are grown at over 1000C you can be sure it is pretty damn high though.
     
  22. Ophiolite Valued Senior Member

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    Do you know that there is more than one use of the term sputtering. This is a science forum, so one would expect that where an ambiguous term is used it is the scientific meaning that is intended. You have used the technical meaning - mere engineering.

    If you are going to adopt a patronising attitude to others, who rightly question your poorly phrased questions, you might at least attempt to possess the level of knowledge you seem to expect from others.

    For the record: "Plasma ions, neutralized plasma particles, pickup ions, and neutralized pickup ions penetrating a gravitationally bound atmosphere can cause molecular ejection from an atmosphere by momentum transfer........it has proven useful to divide the ejection induced by an incident ion into two contributions: single-collision ejection from the exosphere and ejection due to the cascade of collisions occurring below the exobase (sputtering)."

    J. G. Luhmann and J. U. Kozyra "Comment on "Dayside Pickup Oxygen Ion Precipitation at Venus and Mars' Spatial Distributions, Energy Deposition, and Consequences" JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 97, NO. A9, PAGES 13,911-13,914, SEPTEMBER 1, 1992

    Sputtering is viewed as an important mechanism for atmospheric erosion. It may also cause surface erosion of smaller planetary bodies with minimal atmospheres.
     
  23. RealityCheck Banned Banned

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    Hi Ophiolite, arauca, everyone.

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    I'm not sure what all the fuss is about.

    Honestly, since arauca did use the phrase "Why sputtering work in a particular pressure range" (noting especially his term "work" and infering from that that it was 'engineering' process); and also the further phrases "why not in a vacuum 10-8 micron ? or lover" and "why not on atmospheric pressure?", I automatically inferred that he WAS using 'sputtering' in the 'mere engineering' sense, and replied on that basis.

    I haven't seen anything since from arauca or anyone else which would imply definitely that I did not infer correctly at first reading.

    If there was any 'ambiguity' in the question (however poorly put in 'English' it may have been

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    ), I for one didn't pick up on it.

    Was there any other way to interpret his intent/question on "sputtering" given the context/phrases he used, albeit haltingly in English?

    Not arguing, just observing.

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    Cheers!

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    Last edited: Mar 24, 2012

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