Hello Matteo,

Although I share some of your exasperations, I cannot but say that we do have the liberty of not responding to a 'dumb' question. No one can make you waste your time unless you volunteer to do so! This is a forum of > 2.8 million online users from an unimaginably wide spectrum of backgrounds and circumstances - it is just not fair to judge, or be rude to a person we barely know. Questioners will automatically learn to ask questions properly if they do not get useful/any answers to 'dumb' questions.

It depends on the nature of the material. What kind of sample are you asking about?

Masatoshi is right to ask for more specifics. Nevertheless, one contribution is the decrease of coherent scattering through thermal excitation of lattice vibrations. One way to take this into account is through the so-called Debye-Waller factor. If the structure is anisotropic then it may be necessary to take this into account in a more detailed correction procedure (anisotropic amplitudes of mean square atomic displacements). The actual amplitudes depend on the mass of the atoms and thus are different for different atoms in a compound.

What do you mean by 'decreasing XRD intensity'? Maybe your material is converted from one phase into another, which would cause peaks attributed to the first phase to decrease ...

Without more info (material, conditions, ...) is difficult to say something, but as you say, the change on the crystallinity migth be a reason.

In some world I found some people asking questions about some materials in some film form that behaves in a strange way.

I wish I would have such amount of free time! Cause the level of detail of the question suggests it to be a randomly posed one....

It depends on the material and annealing temperature.

Dear Matteo,

I think it was better if you had ask about the material instead typing your thoughts.....

I think your material may be amorphous and not crystalline

so this depend on the nature of your material.

Hello Priyadarshini,

It is very unusual for crystallinity to decrease due to annealing. Generally, the opposite is true unless, of course, as already suggested, there is some phase change. Also, as far as I understand, the sharpness (FWHM) of the XRD peak is the more relevant feature for crystallinity. A decreasing peak height may mean that there is more x-ray absorbing material in the path of the x-ray beam. If the annealing causes oxidation of the material, this is a possibility.

From these arguments and the responses of the peers so far, you may have guessed that the answer to your question needs more information about the material(s) involved. You mentioned that you saw the effect reported in papers. Can you please post the citations (which authors, journals, volumes, pages?) of those papers? We all would like to know as this is very interesting!

Abhay,

you could have saved space avoiding typing your comment as well then... It is CLEAR that this place is becoming more and more filled with poorly thought or completely dumb questions and in most cases also with completely useless or dumb answers.

And this question is a further proof. No details in the question, no answer from the guy in 3 days. So my answer matches the question perfectly.

Do you really think knowing just the material adds some further info? How was the specimen(s) prepared? what is the measurement geometry? are the pattern taken on the same specimen or on similar ones? Why didn't the guy simply post the doi of the paper before asking the question? what does it mean "decrease in xrd intensity?" the intensity of the whole pattern or of a single peak? and if so, which peak and which structure? What does he means by crystallinity (there is a HUGE confusion in the literature about this term)?

This is simply the sign of a NONEXISTENT scientific approach. Nobody working scientifically on a problem poses such vague questions.

Should I say more?

More and more I am convinced that those people pose incomplete questions just to increase the number of answers... as I already said more than once, I would be scared to have a student like that.

This is my thought.

Hello Matteo,

Although I share some of your exasperations, I cannot but say that we do have the liberty of not responding to a 'dumb' question. No one can make you waste your time unless you volunteer to do so! This is a forum of > 2.8 million online users from an unimaginably wide spectrum of backgrounds and circumstances - it is just not fair to judge, or be rude to a person we barely know. Questioners will automatically learn to ask questions properly if they do not get useful/any answers to 'dumb' questions.

Thank you Dr. Knand. I am giving some papers J. Applied Physics 99, 094502, (2006), Applied Surface Science 173, (2001) 352-361. Pl give your suggestions in this regard.

Thank you very much Dr. Leoni for your comments regarding my question. Obviously i will learn how to ask a question in scientific community.

Dr. Leoni, regarding your previous suggestions and questions, i am going through detail of MWH to answer them. Frankly speaking i have no detail idea on this part. I have only gone through some papers. First I have to enrich my knowledge from your suggestion. Then only i will be able to answer them.

Priyadarshini,

This is something very strange. Have you scanned the entire region in 2-Theta to check that there is no texture effects? Also, did you see any new peaks ie. any possible phase transformation? And what was the annealing temp. and time? I mean how the diffusion of atoms affect he compositional homogeneity. I think its quite tough to explain.

Priyadarshini,

I looked at the three papers you cited. The materials discussed are pentacene, phthalocyanine and ZnO. Authors of each paper acknowledge that the observed decrease in XRD peak heights with increase in temperature in their respective material of interest is exception to the common expectation/trend, but do not definitely conclude why.

For ZnO, notably, the best quality crystalline sample (smallest FWHM) they report shows a poor peak height. This clearly tells us that the fall in the XRD peak height is not related to crystallinity of the samples. It might well be, as speculated, that the composition (stoichiometry) of the material is changing as a function of temperature. The resulting defects may be affecting the XRD peak height.

The other two materials are organic and so have stability issues with increase in temperature. The vanishing XRD peaks in these materials may suggest that at higher temperatures they do not remain crystalline at all. I'm not an expert on organic materials; peers of the field may point you the correct direction.

Thanks Dr. Kanad for these suggestions.

...just concerning the ZnO paper, one thing is clear: the refereeing was quite poor, as you cannot accept diffraction data over such a short range and you cannot say there is some texture without providing at least a pole figure.

As I already predicted in my previous question, there is absolutely no information even in the paper e.g. about measurement geometry, specimen preparation and not even about the instrument.

It is quite impossible from the presented data to have a definitive assessment of what's going on... in particular few things are definitely strange:

* nothing is said about the thickness of the films... they say they have a sharp edge for profilometry, at a certain point they mention 500 nm but no info is provided.

* nothing is said on which of the films are presented in Figure 1 (those on Si or those on glass? and do they saee any difference?)

* nothing is presented about the texture of the film. It is quite likely that the film was measured on a traditional diffractometer (otherwise they would have said it's a 4 circle and texture info would have been presented). if the texture axis is a but off (each wafer has its own history...), then you see an apparently small peak simply because you are measuring the shoulder of the pole... the stress contributes to get the picture even worse...

* no comment is given on the "grain size" versus T.. from the XRD data it is clear that the FWHM decreases with the temperature.. thus the domain size increases at least in the 002 direction... AFM shows that the size of the grains on the surface decrease with the temperature.. so either the grains are getting more thin and elongated or we have a problem...

* a ca. 1GPa stress on the film can be easily measured also by XRD.. so why didn't the author verify if their Raman result was correct? Raman is a surface technique and the increase in roughness means that what is measured is the stress in the rough part and not on the "surface" or subsurface region...

Too many open questions that should have already been raised by a referee in 2008...