X-ray Lab Technique

High-Resolution (HR) mode is mainly suited for single crystals, nearly perfect epitaxial layers as well as textured epitaxial layers. This mode can be used for w/2q scan, rocking curve (w scan), and reciprocal space mapping.

In X-ray Lab HR measurements can be done on PANalytical X'Pert 1 diffractometer using the following optics:

Incident Beam:

PreFix Hybrid Monochromator

Diffracted Beam:

Triple Axis/Rocking Curve (TA/RC) attachment

RC part consists of receiving slit

Triple Axis part carries an analyzer crystal

Incident beam monochromator significantly reduces x-ray beam divergence (up to 5 arc sec for Bartels Monochromator with Ge(440) reflection). It also eliminates Ka2 line leaving only Ka1 component. High resolution monochromator is a four-crystal monochromator. The crystals have (110) surfaces and are preset for Ge(220) or Ge(440) Cu Ka1 reflections.

Hybrid monochromator consists of a parabolic graded multilayer mirror (x-ray mirror) and a channel-cut Ge crystal combined in one module. By passing a slightly broader spectral range (~19 arc sec) than 4-crystal HR monochromator, the hybrid monochromator delivers much more intense parallel beam of Ka1 radiation. The Ka2 component is suppressed to a level below 0.1%.

Remarks:

Hybrid monochromators are less applicable for RC measurements at 2q> 90 deg. The hybrid spectral band-pass of a hybrid monochromator is broader than that of 4-crystal HR monochromator. At high 2q angles the wavelength dispersion causes broad diffraction peaks, leading to a decrease in diffractometer resolution.

A small fraction of Ka2 radiation (0.05 - 0.1 %) is present in the XRD spectrum emitting from a hybrid monochromator. It may become visible during reciprocal space mapping with large dynamic range.

High Resolution applications and the required equipment

Application	Incident Beam Optics	Diffracted Beam Optics	Remarks	Notes
Rocking Curve (w-scan)	Hybrid Monochromator	TA/RC Attachment (Receiving Slit Part)	Line focus, highest intensity.	w-scan provides resolution defined by the incident beam monochromator. 2q-scan provides resolution defined by the receiving slit.
	4-crystal Monochromator, Ge(220)		Point focus, higher resolution, lower intensity.
	4-crystal Monochromator, Ge(440)		Point focus, highest resolution, low intensity.
Reciprocal Space Maps	Hybrid Monochromator	TA/RC Attachment (Triple Axis Part)	Line focus, highest intensity.	w-scan resolution defined by the incident beam monochromator. 2q-scan resolution defined by analyzer crystal (~12 arc sec).
Reciprocal Space Maps	4-crystal Monochromator, Ge(220)	TA/RC Attachment (Triple Axis Part)	Point focus, higher resolution, lower intensity.
w-2q scan, phase analysis	Hybrid Monochromator	TA/RC Attachment (Receiving Slit Part)	Line focus, highest intensity.	Only Ka1 component is present.
w-2q scan, phase analysis	4-crystal Monochromator, Ge(220)	TA/RC Attachment (Receiving Slit Part)	Point focus, lower intensity.	Only Ka1 component is present.
w-stress analysis	Hybrid Monochromator	Parallel Plate Collimator	Ka1 only.	The hybrid monochromator allows to determine peak positions accurately since Ka2 stripping is not necessary and the background intensity is very low.
Reflectivity	Hybrid Monochromator	Parallel Plate Collimator	Use collimator slit. Ka1 only.	The monochromatic parallel incident beam reduces the background intensity and improves the resolution.
Reflectivity	Hybrid Monochromator	TA/RC Attachment (Triple Axis Part)	Highest resolution. Lower intensity.	19 arc sec resolution in w and ~12 arc sec resolution in 2q make beam very narrow and parallel.