Bruker-AXS D8 Discover with GADDS Area Detector

This instrument is a state-of-the-art multi-purpose X-Ray diffractometer(XRD) system which will be located in the Center for Materials Research and Analysis X-Ray Materials Characterization Facility.  The purpose of this acquisition is to support the recently awarded NSF Materials Research Science and Engineering Center (MRSEC) grant, as well as individual investigators at the University of Nebraska by providing new capabilities as well as dramatically increasing research productivity.

Common configurations

This system includes the following highlighted hardware:

Large area, high sensitivity, multi-wire proportional 2-dimensional detector allows collection of a large quantity of 2-Dimensional information in a small amount of time.

Sample positioning: motorized Chi(tilt) and Phi(rotation) rotations and X-Y-Z translations.  The cradle accommodates bulky specimens, powders, thin-films, and wafers up to 80 x 50 x 20 mm and weighing up to 1 kg. 

Heating device with an x-ray transparent dome designed for orientation sensitive temperature studies from room temperature to 900 ̊  C in air, vacuum, or inert gas atmosphere. It allows access to the entire diffraction space of a sample when measuring in reflection mode.

Unique hardware allows x-ray tube to be rotated such that the line-focus is in the scattering plane of the instrument which produces very high diffracted intensities when in the grazing incidence in-plane diffraction geometry.  Motorized tube movement out of the diffractometer scattering plane allows accurate setting of incident angle.

Computer controlled video camera and laser pointer for easy and accurate sample positioning and system alignment.

A parabolic, laterally graded multilayer mirror which converts the divergent beam projected by the line focus of an x-ray tube into a quasi-monochromatic and highly parallel (divergence .03 ̊ ) beam of high intensity.  White radiation and Kb lines are virtually eliminated. 

Using the Goebel mirror as a beam conditioner, this channel cut 2-bounce Germanium monochromator yields a beam that is extremely parallel (divergence .007 ̊ ) and monochromatic (only Cu Ka 1) for high resolution applications.

Motorized tilt stage for sample pre-alignment allows tilting of a sample around 2 perpendicular axes which allows orientation of sample normal to coincide with the Phi-circle of the Eulerian cradle.

Motorized module that allows software controlled switching between 2 diffracted-beam configurations.  The first is a high intensity path incorporating a motorized slit, and the second is a high-resolution path incorporating a triple-bounce channel-cut monochromator. 

The system can be reconfigured for the following applications:

In-plane diffraction is a technique for measuring the crystal planes that are oriented perpendicular to the surface.  As a result, the in-plane lattice parameters and crystal orientation can be determined.

Enhance diffracted signal from polycrystalline thin films and examine structural variations as a function of depth by precisely controlling incident angle and therefore the penetration depth of x-rays. 

Measures film thickness, roughness (interface and surface), and density of films (2 nm – 500 nm) Also measures multilayer interface quality and periodicity structure evaluation.

Temperature-induced phase transition investigations, Texture measurements, Stress, profile analysis, powder diffraction, grazing incidence, and high resolution studies.  Point detector can be used for high resolution or area detector for high speed.

Rocking Curves    This is a method for analyzing epitaxial structures for which the layer and substrate are almost perfect single crystals.  These means the difference in diffraction angle for the layer and substrate is very small and requires the capability to resolve Bragg peaks on an arc second scale.   The data is recorded as a rocking curve and can be modeled and fitted to reveal structural details of the epitaxial layer.

Reciprocal Space Maps  This is a technique for analyzing epitaxial (and similar) thin films.  Narrow scans of reciprocal lattice points are performed for various diffractometer settings and the scattered intensity can be plotted in a 2-dimensional frame.

A pole figure is measured at a fixed scattering angle (constant d spacing) and consists of a series of  Phi-scans (in- plane rotation around the center of the sample) at different tilt or Chi angles and measures preferred crystallite orientation.  Measurement times are much faster when using the Hi-Star area detector.

Stress is determined by recording the angular shift of a given Bragg reflection as a function of sample tilt (psi). This actually provides a measure of strain in the sample from which the stress can then be calculated by plotting the change in d-spacing against sin²psi.  This measurement is faster and more accurate when calculations are based on the distortion of the entire Debye ring which is possible when using the Hi-Star area detector.

Small sample amounts, and/or samples which tend to have texture can be prepared in thin glass capillaries. A fast, reliable diffraction pattern can be acquired when the signal is detected over a large portion of the solid angle with an area detector.  Small areas on larger samples can be probed using this method with the laser/video sample alignment and sample positioning of the Eulerian cradle.

For more detailed information and specifications on this instrument, please see the Files page (coming soon).