For semi/non-polar GaN grown on sapphire, we always found that at different azimuth angle, the on-axis XRD rocking curve FWHM is very different. Some paper mentioned that this kind of anisotropic property is related to the larger mosaic tilt, reduced coherent length, or dislocation and stacking fault. But there is still not a clear conclusion about this question. Does anybody know how to analyse this phenomenon? how to distinguish the contribution from different factors?
Generally, an azimuthal dependence of the rocking curves FWHM is related to tilt/twist distribution of the diffraction domains. In order to analyze these phenomena you should perform a series of measurement on different reflections and using the so - called skew - symmetric diffraction geometry (w-2teta symmetric scans buth with the scattering plane non-perpendicular to the sample surface). In this way you can separate the tilt/twist contributions. For more details, check the publication by Moram and Vickers, "X-ray diffraction from III - nitrides" Rep. Prog. Phys. 72 (2009) 036502.
Good luck!
Marco
Generally, an azimuthal dependence of the rocking curves FWHM is related to tilt/twist distribution of the diffraction domains. In order to analyze these phenomena you should perform a series of measurement on different reflections and using the so - called skew - symmetric diffraction geometry (w-2teta symmetric scans buth with the scattering plane non-perpendicular to the sample surface). In this way you can separate the tilt/twist contributions. For more details, check the publication by Moram and Vickers, "X-ray diffraction from III - nitrides" Rep. Prog. Phys. 72 (2009) 036502.
Good luck!
Marco
I'd encourage you to upgrade to a 2D rocking curve imaging system. This will help you understand the Nano structure of your sample and its spatial coherence better. Please review the attached link to the RG discussion (monologue :-) regarding the use of such technique to image the Si-Ge on Si NIST 2000 SRM (standard reference material) sample with a Bruker D8 HRXRD and an OnSight AXIS-TAS25 (Advanced XRD Imaging System).
Also attached are images from a Pt thin film on Si substrate sample measuring "Roll & Twist" or "Tilt & Twist" with real time XRD topographic images (Panalytical X'Pert). Comments and suggestions will be appreciated! We viewed the Pt (111) and Si (004) reflections for this relative "Twist & Tilt" measurement without having to resort to RSM! Real time!
P.S. All images may be downloaded for measurements.
https://www.researchgate.net/post/What_is_the_best_way_to_interpret_REAL_TIME_3D_X_Y_Omega_2Theta_reciprocal_space_relative_intensity_data_from_HRXRD_rocking_curve_analyses
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