X-ray Diffractometer PANalytical XPert PRO

X-ray diffractometer Panalytical X’ PERT PRO MRD Extended is intended for studies of fine structural features of single crystals and hetero-epitaxial films with thickness in the range several nm to several mcm.  APrefix system enables replacing  first stage monochromators, depending on the tasks, with no additional re-adjustment. The X-ray mirror forms monochromated beam of the 5´10⁹pulses/s intensity  (150’’ beam spread), which is best suited for studies of imperfect single crystals and polycrystalline samples. A hybrid monochromator, consisting of a combined in a single block  X-ray mirror and bi-crystalline slit germanium monochromator, provides 400´10⁶ pulses/s intensity with beam spread of  25’’. Optional recording of fragments of reciprocal space areas in the vicinity of the selected reflex and reflectometric curves  in order to determine z epitaxial layers thickness. A combination of the X-ray mirror and four-crystal germanium monochromator  in the “Extended” geometry provides 26mln pulses/s intensity with a beam spread of 12 ’’. The intensity of the monocromotized beam in the “Extended” geometry increases by a factor of 18. For examples, application of the rotating anode tube in the Rigaku diffractometer provides intensity enhancement a factor of 9 only. Optimal application of this feature is rocking curves recording of symmetric and asymmetric reflexes in order to determine composition and thickness of epitaxial layers  and superlattices period. The diffractometer is equipped with the 3^rd crystal–analyzer for precise measurements of the lattice parameters inverse space areas recording. The process of two-dimensional pictures measurements is fully automated. The diffractometer is equipped with software package for the analysis of rocking curves and two-dimensional reciprocal space areas.

 The difractometer enables  studying of samples by five various methods.

1. Recording of the rocking curves for sample and analyzer in order to determine lattice parameters of epitaxial layers perpendicular and parallel to the substrate plane. The method is used for measurements of the composition and thickness of epitaxial layers.

2. Reflectometric curves recording for small angles of incidence of X-rays on the sample. Refraction index of X-rays in crystals is less than unity by a few times in 10^-6, therefore full external reflection of X-rays is observed below a critical angle value ( q _с= 0.22 ° for Si and  q _с=0.31 ° for GaAs). Above the critical angle values,  a system of reflectometric maxima is observed, which enables to determine the thickness of epitaxial layers, and  intermediate layers with 0.1nm accuracy.

3. Fragments of the reciprocal space area in the vicinity of the selected reflex by integrating from several tens to hundreds of rocking curves into an overall two-dimensional picture, within the Panalytical Epitaxy program. It is used to disentangle contributions to the reflexes broadening from  lattice parameters variations  and from misorientation of some of its layers.

4. Reflexes recording in the diffraction sliding geometry, where the sample is tilted by a y =55 ¸ 85 ° angle around horizontal axes, lying in the sample plane. In combination with asymmetric reflexes this enables to decrease smoothly the X-ray penetration depth into the sample from several microns to hundred and less nanometers for detection of the layers with lattice parameter, close to that  for the substrate.

5. Two-dimensional X–Y plots scanning in the real space for determining the structures curvature radius and for revealing local imperfect areas.

 Technical parameters.