How are you measuring the single crystal? Are you measuring it with a X-ray powder diffractometer? You will not see all reflections unless you orient the crystal properly. In powder diffraction you see all possible Bragg reflections. There is no need for orientation because the crystallites in powder have all possible orientations. The proper way to measure a single crystal is to use a four-circle diffractometer where you can orient the crystal properly.

Thanks for reply.

Its true that the crystal is not oriented (both psi and other angle is zero) at all. But it does show a single peak as you can see in my attachment. But this peak should have been observed in powder pattern as well. Does this peak indicate direction of growth?

All Bragg peaks are associated with lattice planes characterized by Miller indices (hkl). The direction of growth as such has nothing to do with the Bragg peaks but if the growth direction is coincident with a crystallographic hkl direction then you will also see a corresponding Bragg reflection. So you have to orient the crystal properly and find out the possible hkl values of the the reflection you have found. Otherwise just crush a part of the crystal and do powder diffraction and check whether you get the same diffraction pattern as you saw before from powder sample and aklso check whether you can see a Bragg peak at 74 deg. In any case you should check the quality of your single crystal by back reflection Laue method. Is the structure of the compound known in literature? In that case you can calculate whether you should see a reflection at 74 deg. or not.

By the way I cannot read your InSbN2_single_peak.caf file in my computer (mac) so I cannot see the peaks you observe. Can you transform it to a pdf file?

I see you can index your single crystal peak as 511. Now you must check the extinction rule of the space group your crystal belong to. Is this reflection allowed?

I think I should give more details. Basically I have grown single crystal of InSb doped with nitrogen. Initially, I crushed a part of crystal and taken pwder xrd that I had mentioned.

Now when this single crystal x r d was carried out, Since orientation was not known, phi and psi values were put zero and we did get a single peak, which was not observed in powder xrd done earlier.

So should I rotate and check for another may be of higher intensity peak which will indicate the growth direction?

I cannot transform to pdf, sorry. but this file that I now attach may open in excel

InSb is FCC with space group F-43m. This reflection is allowed. Not expecting any structural changes with addition of N as % is very small

Thanks for discussion

Manisha! Your data: http://www.flickr.com/photos/85210325@N04/8782658806/

Use Excel & Paint to create such plots instantly.

You have only one peak? Operator error!

What you really need is a portable 2D real time XRD Microscope for the single crystal work. There is one in Bengaluru India and another in NJ USA. This has to definitely do with the orientation as the "Guru" Tapan has already mentioned. In 1979-1986 (Rutgers & JHU), when I had a similar set of challenges as you today, I immediately moved on to 2D real time XRD imaging. The real solution! You'll get your Ph.D done in 2 years or less. Good luck Manisha!

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Yes you should rotate the angles and try to find other strong reflections and determine the orientation matrix.

Can you please tell me what is your goal? Do you just wish to check whether the single crystal is good or you wish to get more structural information viz. how much N has got into the lattice and where are they?

You are lucky you got at least one reflection. So, in your case for that particular orientation Phi & Omega (Phi - rotation about the wafer surface normal, Omega - rotation about the diffractometer axis or rocking axis) you got one (hkl) to be in or near Bragg condition (depending on the solid angle covered by your 0D point/scintillation counter/detector. The other planes would never be in reflecting position along the diffractometer plane unless higher order reflection. As suggested earlier, the powdering method allows multiple orientations of the crystallites hence always having some crystallites in Bragg condition along the diffractometer equatorial plane.

If you cannot do 4-circle measurements and if you have enough matter, the better thing is to crush a part of your crystal and make a classical power diffraction, then index the different peaks.

For the existence of this peak:

- I guess the substitution might have some effect

- double diffraction might happen some times in case of perfect single crystals

Thanks a lot Ravi Ananth. I have been reading your answers to others questions as well and always appreciated your kindness.

Primary goal was to check whether it is a single crystal and to find growth direction.

I had tried to get information on N% from EDAX which failed. WDS has given %of N in the sample. But I am not aware how to get this information from xrd. I have compared peak shifts with respect to undoped InSb but the variation in 2theta value in powder xrd is not same for all peaks. ( for some value +ve change for some values -ve change)

The quality of the crystal and growth direction can be found either from the diffractometer (4 circle) or by the Laue method.

You cannot determine N doped in InSb because N concentration is probably very small and also because N does not scatter X-ray very much. You can do better with neutron diffraction because N scatter neutrons well. But that all depends on how much N you have in the lattice.

Cool Manisha! Tappan is right as usual.

Would you please describe your sample better? Size, thickness, morphology etc. A photo would be perfect both of the sample and the XRD equipment used.

What was your approximate beam size?

Do you have the ability to conduct rocking curve analyses?

What is the smallest angular step possible?

Do you have Phi rotation capabilities?

Have you determined the sample surface orientation or do you have a guess?

You may map both the "relative dislocation density" & the "relative orientation" over the wafer surface by adjusting the sampling size (beam size @ sample surface). Assuming the detector window is "slit-less".

To determine growth direction as Tappan already detailed, use the Laue back-reflection method perpendicular to surface of interest. This is the conventional technique and will give you the answer you are looking for. It is cumbersome and you would have to do some actual work and analyses that will help you train better. If the diffracted beam (spot) size is about the same as the incident beam then that implies your X-ray beam is on a mono-crystalline area of your sample.

However, there is a quick and dirty way with the diffractometer you are currently using. You'll have to learn how to optimize a reflection for the veritable "Rocking Curve Analysis". This entails aligning the (hkl) planes, one direction parallel with the diffractometer rocking axis. Optimization involves trying to get all the above three co-planer & parallel. With a 0D detector, that is not an easy task and I lack experience. "Piece of cake" with a real time 2D device. Once you "optimize", then by geometry you may be able to infer the growth direction.

BTW it would be impossible for a reflection to be absent in the powder and present in the single crystal except due to preferred orientation. You may have some other reflection skew possibly? Put a piece of film in front of the detector and check without any slits on either end.

" I have compared peak shifts with respect to undoped InSb but the variation in 2theta value in powder xrd is not same for all peaks. ( for some value +ve change for some values -ve change) " if you are able precisely measure this then you could build the anisotropic crystallographic strain tensor as a result of the N in the lattice. In other words, infer/estimate the N content.

Amorphous content will not make a crystalline peak disappear in the powder pattern that was present in the single crystal form. Only preferred orientation may, from my understanding.

Certainly post such questions and others like it on the following LinkedIn Group posts when possible:

1. X-ray Diffraction Imaging for Materials Microstructural QC:

http://www.linkedin.com/groupAnswers?viewQuestionAndAnswers=&discussionID=189258615&gid=2683600&commentID=140532636&goback=%2Eanp_2683600_1369907189536_1%2Eamf_2683600_12045948%2Egmr_2683600&trk=NUS_DISC_Q-subject#commentID_140532636

2. X-Ray Diffraction and Scattering Techniques

http://www.linkedin.com/groupItem?view=&gid=3614857&type=member&item=241973911&qid=ae9fa84f-1f22-47b8-9f9b-c529426e3119&trk=group_most_recent_rich-0-b-ttl&goback=%2Egde_3614857_member_244782133%2Egmr_3614857

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Thanks to all

As Tapan said the N content is indeed small, about 0.3% maximum.

and phi rotation facility was available where I had given this sample.

But I will do Laue pattern from wherever available.

There are many nice suggestions. I will try.them