sure that your film is not textured? I have already seen people coming to the lab with "amorphous" specimens that were simply strongly textured films grown slightly misaligned with respect to the specimen normal. Have you done a proper pole figure measurement before coming to the conclusion that the film is "X-ray amorphous"?

sure that your film is not textured? I have already seen people coming to the lab with "amorphous" specimens that were simply strongly textured films grown slightly misaligned with respect to the specimen normal. Have you done a proper pole figure measurement before coming to the conclusion that the film is "X-ray amorphous"?

Thanks for the answer.

As I said x-ray diffraction shows no phase except the substrate peaks from WC and Co. While in powder x-ray diffraction shows phases of TiN and AlN in as-deposited state to annealing up to 1100 degree. No, I have not done any pole figure meas.

You need to do cross sectional TEM with electron diffraction to investigate this problem. There are several possible reasons for no-peaks XRD patterns.

What is the thickness of the coating? I may happen that film peaks are too weak as compared to the substrate ones and you just don't see them. Low angle XRD migth be helpful.

If thickness of your coating is less than 1 um. Then Glancing / grazing angle XRD must be done otherwise you will see only substrate peak.

Matteo has given what I expect is the right answer, but let me try to elaborate. Most likely under the conditions you have described, your thin film sample will be crystalline same as your powder. But if the crystal growth direction is highly anisotropic (as often the case for films) then you will see perhaps only a few, or possibly no diffraction peaks when using a powder diffractometer (I'm waiting for Ravi to jump in here expostulating the virtues of a 2D detector). A couple of pole figures would resolve this, as Matteo has suggested, by revealing the off-axis orientation of the planes.

If this is confusing, think of a silicon "zero background" plate. It is fully crystalline, but you will see no peaks on a Bragg-Brentano powder XRD machine because the crystal is deliberately cut off-axis, so that no diffracted intensity will reach the detector.

I agree with the comments above regarding the coating thickness. Check the attenuation length for your experimental settings such as wavelength and angle of incidence (http://henke.lbl.gov/optical_constants/atten2.html). From the information you provided I would think that even at 1micron thickness and and a tilt of 70 deg you should see peaks - if it is crystalline.

Sergei and Rajib are correct that for a very thin film, the diffraction pattern may be difficult to resolve, especially in the presence of a strongly scattering substrate. In such a case, grazing incidence diffraction can help resolve the film by working at a low incident beam angle so that the x-rays do not penetrate into the substrate.

As stated in my previous post, I do not think that that is your issue here, but I may be mistaken and it certainly couldn't hurt to try it.

LOL! Thanks for the warning Edward Andrew! Here it comes. Let us just consider the time invested by an XRD professional today 2014, over a hundred years after the Braggs got the Nobel Prize. Just to generate a 1D spatially "blind" diffractogram and be left totally guessing as to the Nano structure, is pathetic to say the least, 30-60 minutes! Make a resolution and "chuck the beast" for the New Year!

If you can't get the funds for the purchase or lease of a cost effective real time 2D XRD Imaging devise then at least settle for the good old 2D dental film. Even the dentists these days have moved on to real time imaging of teeth. You may get hold of what they don't need any more.

Bottom line: You would have figured out in real time the nature of the film no matter what the thickness or morphology by virtually "groping" through the reciprocal space.

That said, if you get a firm understanding of the fundamental XRD principles involved then you should be able to use your present XRD instrumentation with the copious advise already bestowed up on you by the RG experts ahead of me, to verify any hypotheses you come up with explaining your linear equatorial diffractogram. Most likely a half diffractogram (2-Theta 0-180 degrees). An internal/external standard will make your life a lot easier. Beware of Rip Van Winkle-itis!

BTW We just expanded our detector range from 25mm-40mm (real time) all the way to 300mm flat panel and beyond. Stop the suffering!

http://www.flickr.com/photos/85210325@N04/11343736043/

It depends on the thickness that is why they appear different

The thickness of coating is around 3 um. I have performed TEM also as some people suggested and it showed different phases (cubic and hex).

What I have found about this material system or material system with higher Al >70% content shifts to noncrystalline side which makes them to appear x-ray amorphous.

Thanks to all people.

yes Grazing angle x-ray is helpful in that case.

Hassan! 3um is pretty "thick". What is the expected extinction depth for this material? We've demonstrated significant diffraction (004) intensity from even a 50nm MBE film of LaSrCuO4 (epitaxial). If the sample is not properly oriented (Omega, Phi, Chi) this sample would also appear "to be x-ray amorphous" similar to your experience. However, the term "x-ray amorphous" may be a misnomer in the sense that amorphous materials do actually have a signal whereas oriented thin film would have a significantly different scattering profile (e.g., "Phi scan"). Especially, the diffused scattering components. As suggested earlier (by Matteo & Edward) try eliminating the probability of preferred orientation distorting the "as-is" diffractogram.

Let me summarize your scenario again:

1. Your substrate consists of randomly oriented poly-crystalline bulk of WC & Co. How was this substrate produced? How thick is the substrate?

2. Your film of TiAlN 3um thick was deposited using what technique?

3. Why don't you share your XRD & other data so that we may all have the same advantage as you in analyzing and making recommendations?

4. What sort of XRD instrumentation do you have direct access to?

5. When you state "showed phases (cubic and hexagonal) in powder x-ray diffraction", what do you mean? Did you actually take the combination of the substrate and film and "powder" it before XRD? Are you suggesting a link between powdering (deformation) and crystallinity?

6. Do you have any conventional optical micrographs or TEM data for your samples?

7. The better the input data, the better the output. Otherwise, garbage in garbage out! Help us turn all this in to useful XRD energy! Incidentally, that is what I do for a vocation. Turn trash (medical waste) to cash (energy)! Trash 2 Ca$h!

Have a safe New Year celebration! Happy New Year!

http://www.youtube.com/watch?v=qGG78GKDa7w&list=PL7032E2DAF1F3941F

Hey Ravi. Thanks for your interest and Happy New year.

1. I do not know how the substrate (WC-Co) was produced but the thickness was around 5 mm.

2. Deposition technique was Cathodic arc evaporation. Material is TiAlCrN with 73 at % Al and 24 at. % Ti.

4. what do you mean by what sort of XRD? the technique utilized was theta-2theta and name of instrument is Idefix.

5. What I meant by phases in powder form is the peaks from the powder standalone. Nothing is their except the powder of the material. Substrate was removed by some grinding and use of acid subsequently.

6. Bright-field image with HRTEM is attached.

Great data Hassan! Now observe the responses from others more erudite than I. The RG "prescriptions" will improve dramatically. My knowledge is limited in your field of expertise, HRTEM.

Please do share the XRD data, particularly. I must presume you are using the ubiquitous "powder diffractometer" acquiring an equatorial scan with a conventional 0D point or scintillation counter/detector. This is the first I am hearing of "Idefix" (cute), since my involvement with XRD & NDE in 1979 @ Rutgers and @ JHU subsequently. ("I have drunk from many river banks"). Please do include dimensions and details of optics used. Slit size, radius, monochromation, etc.

"Substrate was removed by some grinding and use of acid subsequently". How thin can you leave the substrate by this process? If you can leave it thin enough to conduct transmission Laue XRD analysis, you'll see the Nano structure in real time on your "Lab Top". With both W & Co, you are working with high XRD absorption factors and diminishing extinction depths. Please compute these ahead of time. Check literature. If you do not have access to a real time 2D XRD imaging devise, then find the oldest and closest dentist in the neighborhood and buy up all his dental film. Polariod film would be great but they may be illegal if not extinct. You may need to go to some remote part of the world to still find those. Lol! I got a whole bunch dental film yet.

Below are some examples of the use of real time XRD Microscopy in the transmission Laue mode. One of my favorites! Aluminum Foil (0.2mm thick) with "preferred orientation": http://www.flickr.com/photos/85210325@N04/7944785794/in/set-72157632728981912

Other foils (0.2mm thick) including Cu, Brass, Ni, Al: http://www.flickr.com/photos/85210325@N04/8008714677/in/set-72157632728981912

Composites (2mm thick) with amorphous constituents: http://www.flickr.com/photos/85210325@N04/7988760159/in/set-72157632728981912

Definitely a good time of the year to "resolve" to acquire a real time XRD Microscope attachment for your dinosaur diffractometer.

Hey Ravi..

Thanks for the valuable replies.

What I known about the instrument (XRD) is its name only Idefix. I am sorry that I do not have all of these information that you have mentioned radius, slit size etc. For TEM, I made all of the samples by my hand though I also get some scarves on my fingers to make then very thin compatible with TEM. The powder was obtained from first mechanical grinding of iron coated stripes then remaining was dissolving in acid for complete removal of substrate. Yes it shows crystallinity in ED pattern from HRTEM which you also have mentioned. I highly appreciate your interest. Thanks

As I have mentioned earlier for coatings with high Al content >70 at % the coating consists of mixture of cubical and hexagonal phases and also the grain size becomes very small in fact around 1-3 nm. Which also the reason of not showing any phase in wide angle XRD performed on coatings.

"grain size becomes very small in fact around 1-3 nm" - What is the typical "unit cell" size? You should be able to sense the 1-3nm size in the SAXS region possibly. Let us review your current XRD data. Please post them.

Please read and assimilate the following book as soon as you can if you are serious about taking advantage of the capabilities of the simple yet powerful tool known to us as XRD for at least over a century now.

Hassan Saleem, this is a beautiful challenge, but there could be some tricky issues.

You prepared the coating, but I could not see on what material.

If the coated material itself is non-crystalline, such as glass, the film will be highly amorphous and the issue will be understandable. The films (despite being thick) would then involve amorphous material (or at best very small nano-particles) to be measured.

On the other hand, the powder involves independent particles (nano- or larger particles) which may have some crystallinity to show XRD.

I will be happy if you could tell me what the substrate was. If amorphous (like glass) please prepare the films again on other types of substrates such as Ti or Al, hoping you get epitaxial growth lattices good for XRD.

I appreciate your feed back

Wishes for you Hassan

Assalam Alakum Hikmat Hilal

Good to read your reply and thanks for taking interest. The substrate is 5 mm thick made of WC-Co. As I have mentioned earlier the reason of not showing any peak from the constituent elements or their compounds (TiAlCrN) is the amount of Al which is 74 at. % which drag the whole matrix towards nanocrystallinity. The grain size is in the range of 1-2 nm which is confirmed by HRTEM. Also the coating is abundant in defects.

Regards

I think that the reason is now clear. The grains in the film are too small to give XRD.

Best wishes

I really agree completely with Professor Hikmat Hilal. The answer is complete and comprehensive

Coherrence of the diffracting domains is usually the culprit. Never heard of "small diffracting domain size" to cause complete XRD signal loss. I could understand the FWHM increasing but not total lack of signal. 3um is a lot of sampling volume to cause no XRD signal (crystalline or amorphous). Unless you verify by recording XRD data after re-orienting ("Phi" rotation) the sample w.r.t. its surface normal, "preferred orientaion" as a cause cannot be eliminated. As I've mentioned earlier, a simple dental film will illucidate any presence of "preferred orientaion". Chances are that due to the amorphous substrate and the accompanying lattice mismatch, the film would have huge misfit boundary layer and hence large micro-lattice "strain" components due to defects.

Shalom Aley Chime!