From the start if you have shifts in peaks, some of them is shifting to lower angles and the others at higher angles , this means that you have a misalignment in your systems and you have to correct it first.. Increasing temperatures will increase the lattice parameters and decrease the FWHM  (not increase).. The decrease in the FWHM is due mainly to increase in crystallite size and decrease in the strains due to annealing at higher temperatures. or You may have Wrong Results From the begining during your film deposition which may come from shifting between deposited layers during your preparation  

Shifting of peak position to lower angles is related to increased lattice spacing when Pt is deposited on MgO substrate whereas change in FWHM is related to change in particle size and is given by Debye-Scherrer equation.

Lattice constant could change due to foreign atom incorporation or platinum oxide formation or Pt-Mg alloy formation. I need to check the relevant data to see which of these could explain your results.

The change in FWHM could be either due to change in particle size (and is given by Debye-Scherrer equation) or it could just be an artifact of the above changes. For example if you have a mixture of compounds with small changes in lattice constant which cannot be resolved then that could appear as a change in FWHM.

Ali,

  The change in temperature can cause changes as mentioned above, but can also cause other changes in resultant film: growth mode, preferred orientation, thickness, composition, strain, etc.  Some of these mentioned properties can manifest themselves as peak shifts and peak broadening.  So, to really understand the changes to the XRD results, you would have to dig deeper into other observable properties. 

  What is the thickness of the films deposited at different temperatures?  Can you index the XRD pattern of both films?  Start by answering those two questions, and you should be able to start understanding the changes you've made to film growth.

Thanks Ravi Kishore.. really supportive Answer.

thanks Patrick, the thickness is around 30 to 40 nm but i don't think thickness is contributing in this change because all the deposition parameters are same so the ablation rate of Pt. may be it will change some thickness with temperature but ...still confused.  orientation of substrate is MgO (100) only one peak of Pt (200) is observed with the same orientation. 

I was asking about the thickness, b/c very thin films could be pseudomorphic (lattice of the film is strained to match the lattice parameter of the substrate, dislocations have not yet formed).  30-40 nm is probably too thick to be pseudomorphic, but that depends on the mechanical properties of the materials and the lattice mismatch.  Growing thicker films could shift the Pt (200) peaks towards their textbook values, and also result in narrower peak widths.

A more likely scenario could be a difference in thermal expansion of the two materials.  Depending on what reference you use for the coefficient of thermal expansion, MgO could have 50% higher CTE than Pt (14 vs 9E-6 per K).  So, even if the initial lattice mismatch is not an issue during deposition, upon cool-down the substrate will contract faster than the film, stressing it.  Stress due to thermal mismatch upon cooling from high temperature growth could certainly cause peak broadening and shifting.  Obviously, your room temperature deposited films would only suffer from a "static" lattice mismatch.  Both effects should be considered to determine if the film is under compressive or tensile stress  as a result of deposition temperature changes.

hi...FWHM would be related to crystal quality and crystallite size, smaller sizes would show higher FWHM...also laser ablation produces particulate, probably that has related too with respect to temperature...shift of peak could be related to several factors, whether any regular trend it follows or no that need to be verified...

Shortly, peak positions are related to the lattice parameters. If you observe them the diffracting lattice in the considered volume is changing.

If FWHM is changing, everything what affects the size of the coherent volume is affecting this: smaller volume by smaller size or high deformation (which also means smaller size). The last one also includes a variation of the lattice parameter by a) strain, or b) variation in chemical composition, high vacancy concentration, ordering. Finally, all of them can occur at the same time so that it is hard to say which effect is the one which is responsible for your observation, especially if you are talking about the thickness of 30-40 nm. Then even the number of grains may affect the visibility of specific reflections. 

Well most of the answers cover all the important point. But there is a trivial issue of zero error of the instrument. If you are not finding thickness dependence in the shift (and the range of thickness is appreciable), it would be advisable to ask the operator if he had done a calibration run of the instrument or not.

I totally agree with Arun Palakkandy. Before getting lost in theories about what might have caused the shift, make sure that the device is perfectly calibrated. If it is not, you will observe peak shift AND FWHM broadening.

From the start if you have shifts in peaks, some of them is shifting to lower angles and the others at higher angles , this means that you have a misalignment in your systems and you have to correct it first.. Increasing temperatures will increase the lattice parameters and decrease the FWHM  (not increase).. The decrease in the FWHM is due mainly to increase in crystallite size and decrease in the strains due to annealing at higher temperatures. or You may have Wrong Results From the begining during your film deposition which may come from shifting between deposited layers during your preparation  

Is the Pt oxidized to an oxide form (with increase in lattice parameters) such as PtO2?We also have migration and sintering of particles and thus decrease in peak width.

Dear Alan

It is possible of PtO formation..but by XRD reference of JCPD I find the exact same peak for Pt. 

Yeah Arun  I do calibration about thickness. By using x-ray refractometery method.

@Karimat: you can also have shift of peakes to lower AND higher angles if the symmetrie reduces.

@ Claus: when FWHM is remarkably changing if the system is not well callibrated? And how big the miscalibration must be? And what is the tendency with 2 theta?

@Gert: As I observed FWHM changes mostly, when the sample was not well-prepared, it is not easy to say. I only can say that the FHWM increased significantly (meaning that it could be seen just by looking at the diffraction pattern), when the sample was about 0.2 mm too high. What this means for the 2Theta shift depends on the geometry of the system. The best thing would be just to check this by controlled misalignment of the goniometer. I did this before, but I can't remember the exact numbers of the 2Theta shift.

I have some experiences with broadened XRD spectra and shifted pattern. During my working with XRD I investigated different materials (FeZrB, Finemet, Cu,...).

Broadening is a sign for crystallite size and microstrain/-stress in your material. And crystallite growth depends on temperature. I examined the influence of temperature on crystallite growth, as well as the possibility of annealing. Eventually the temperature influenced the building of more small crystalls. 

For this purpose i had to prepare my testpieces at special temperature for special time. Of course my surface was not that plain that i wanted to after the this treatment, therefore a shift of my xrd pattern was a result.

Thankyou DiDi for sharing your experience.. it's very useful for me. 

Search online and pull out the equation involves FWHM and 2-theta angle. You will see. Then you will notice the FWHM is related to your grain size and 2-theta angle is related to your d-spacing. Though these exclude any operational and experimental errors.

Please post your XRD data for the best feedback on RG. Excel format would work :-)

Please describe your sample better.

• Substrate MgO poly or mono crystalline?
• Orientation, grain size, etc.
• Film thickness? Include processing conditions and environment.

Please describe optics and XRD instrument used.

What is your objective with XRD? What XRD equipment do you have access to?

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Temperature is one of the important factors which influences the crystalline size of particles under the study. During the change of temperature from RT to 600 C , there might be sort of changes in crystallinity of Pt just like phase changes, origin of new planes, strain effects etc., might be the considerable reasons for the shift in the peak positions of your results............

Do you see these changes when you change the substrate (from MgO to some other lattice matching substrate? If no, then it is difficult to explain these changes based on temperature alone.

Can you get us the lattice constants of platinum oxide, Pt Mg alloy, MgO and Pt? It will help us answer the question. I have the data for some of them, but not all.

@V.N Ravi ...I am calculating the Lattice constant of Pt, But its strange that by using the right values of peak position (Gaussion fitted peaks) I am unable to get the right value of the Pt lattice constant. can you help me in this matter too.  As in Bulk value of Pt its 3.91A' , lattice constant for PtMg (when its in 50% concentration) is 4.86A' when its in Pt=86% concentration then Lattice constant is 7.82A' ..lattice constant of PtO is 3.20'A. I am sending you the papers form which i have taken these values