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New optics for X’Pert PRO The hybrid monochromator for high-resolution measurements
Contents • What is a hybrid monochromator? • For which applications can it be used? • What is the advantage in the analysis of epitaxial layers?
What is a hybrid monochromator? • A combination of an X-ray mirror and a channel-cut Germanium crystal • Only Cu K1 is transmitted • The combination gives a high-intensity, parallel, monochromatic X-ray beam • Two varieties: • two bounces in the monochromator • four bounces in the monochromator
For which applications? • Two-bounce type: • Phase analysis on rough samples with complex patterns • Samples in glass capillaries • Four-bounce type: • Measurement of rocking curves and reciprocal space maps
GaAs } 8 x AlAs GaAs substrate Example: measurements on a superlattice • What is a superlattice? • What is the layer thickness?
Which instrument? X’Pert PRO MRD: • Standard MRD • Extended MRD
Standard X’Pert PRO MRD • Tube focus: point • Ge(440) monochromator • Ge(220) monochromator • Tube focus: line • four-bounce hybrid monochromator
Normal MRD: conclusions • Features of the hybrid monochromator • Intensity increase: • > 30 compared with Ge(220) point focus • > 10 compared with Ge(220) asymm. • Fast, compact tool for reciprocal space maps and rocking curves • How can this be compared with Extended MRD?
Extended MRD • Mirror with Ge(220) and Ge(220) asymmetrically channel-cut monochromator • Compare with four-bounce hybrid monochromator • and with Ge(220) point focus
Conclusions (2) • The four-bounce hybrid monochromator is an excellent tool for fast measurements of rocking curves and reciprocal space maps • It can best be used when high intensity is required in combination with moderate resolution • When ultra-high resolution is required, it is easy to change to a four-crystal monochromator