• Bruker D8 X-ray Reflectometer.
  • For the determination of layer properties like thickness, density and roughness.
  • Can be applied to thin films (liquid, amorphous, poly-crystalline, epitaxial or any combination), prepared on both solid and liquid substrates.
  • Measurement of layer thickness (between 0.5 and 400 nm), density and roughness (between 0 and 2 nm) with about 1 % accuracy, independently of each other
  • X-ray Source is a 2.2kW Cu anode long fine focus ceramic X-ray tube. The running conditions for the X-Ray tube are 40 kV and 40 mA, the power supply controls these with a stability of better than 0.01% for the high voltage and 10% of the variation of the supply for the current.

Please see the Measurement tab for examples of the applications of this instrument.

 

 

Technical Specification


This instrument is based around a two circle goniometer, enclosed in a radiation safety enclosure.

X-Ray Source

The X-ray Source is a 2.2kW Cu anode long fine focus ceramic X-ray tube. The running conditions for the X-Ray tube are 40 kV and 40 mA, the power supply controls these with a stability of better than 0.01% for the high voltage and 10% of the variation of the supply for the current.

X-ray Beam Shaping Optics

The beam is collimated, compressed and frequency filtered by a Göbel mirror and V-Groove. To produce a collimated beam (with a divergence of below 0.007 o) with dimensions of about 0.3 mm by 11 mm

The 60mm Göbel mirror is a multilayer X-ray mirror on a high precision parabolic surface. The lattice spacing gradient and material combination is optimised for the Cu-Ka1 part of the radiation spectrum whereas other wavelengths are suppressed by several orders of magnitude. This gives a very reflective (95%) optic that not only collimates the beam but acts a monochromator.

The V-Groove is a perfect germanium crystal with a V-shaped groove etched and polished into it. This compresses the beam via asymmetric 022 reflections within the Germanium crystal. Because it is wavelength specific it also spectrally cleans the beam so that only Cu-Ka1 is present in the controlled beam.

Goniometer

This is a high precision microprocessor controlled, two circle goniometer with independent stepper motors and optical encoders for the Theta and 2Theta circles with the following specifications:

Maximum measurement circle diameter 250 mm
Minimum measurement circle diameter 100 mm
Smallest angular step size 0.0001o
Reproducibility +/- 0.0001o
Maximum rotational speed 1500o/min
Angular range (Theta) -5o to 40o
Angular range (2Theta) -10o to 60o


Reflectometry Sample Stage

This stage is manually adjustable for height and tilt and can accommodate samples up to 200 mm in diameter and 50 mm thick. Samples are held on the highly polished stage by suction. The stage features a knife edge collimator to enable fast precise positioning of the sample. This also helps to improve collimation of the beam and stop radiation scattered by the air before the sample from hitting the detector.

Detector

The detector is a NaI dynamic scintillation detector with a maximum count rate of 2 x 106 s-1 (although it should not be exposed to in excess of 5 x 10 5s-1 for periods longer than about 1 second). A computer controlled absorber is mounted directly in front of the detector and is used to attenuate the beam by about 2 orders of magnitude. To change the angular resolution several slits (0.05 to 2 mm) are available to be placed in front of the detector, as are a set of Soller slits to allow for small samples. Attenuators made of Cu and Ni are also available and can be manually placed in the beam, by inserting them into the slit holders in front of the detector. The detector electronics are capable of a count rate up to 3 x 107 s-1.

Software

The software suit is all windows based, and enables the user to both acquire and analyse data. Data acquisition is possible both directly by the immediate measurement program Adjust and the automated Job program via a DQL file. In the later case the data can be displayed in real time using the display program. Two analysis programs are available, one for diffraction and the second for reflection.