X-rays are electromagnetic radiation with characteristic wavelengths of a few Angstoms, comparable to the lattice constants of crystalline materials.
As such, x-rays incident on the planes of semiconductor can exhibit wave interference phenomena, much like light reflected from a periodic grating.
Given knowledge of the x-ray wavelength, measurement of the incident and reflected beam angles permits calculation of the spacing of the crystal's planes in accordance with Bragg's law.
The technique's precision makes x-ray diffraction analysis an invaluable tool in the determination of crystal structure, planar spacing, and material composition. Modelling of results can provide additional information indicative of crystal quality, layer mismatch and stress, defects and misorientation, mosaicity, surface curvature, and relaxation.
The CEDT operates two XRD systems.
The Bede D1 system's internal Si crystal monochromator makes the instrument suitable for diffraction measurement of most crystalline materials and wafers. Its 12 independently controlled motors also open up a range of additional measurement techniques, including powder diffraction analysis and glancing angle reflectometry.
The Bede QC1 is a dual-crystal rocking curve analysis system. The instrument is suitable for measuring the rocking curves from InP and GaAs based materials.
The CEDT's x-ray facilities are available to CEDT members.
Only trained operators are permitted to run the instruments.
In cases where only a few samples are to be tested it may be far more efficient and cost-effective to have samples scanned by a CEDT staff Research Engineer, rather than participating directly in operator training.
The x-ray facilities are also available on a fee-for-service basis to McMaster University affiliates who are not CEDT members.
Subject to scheduling availability, the x-ray facilities may also be available on a fee-for-service basis to potential users unaffiliated with McMaster University.
Fees associated with the use of the CEDT's x-ray facilities are used to pay for the maintenance and up-keep costs associated with the systems; the x-ray tubes, power supply units, motors and control electronics all have a finite lifetime. Fees also reflect operator time committment.
Trained operators can book the Bede D1 XRD system via the sign-up form outside room TAB 110/B.
However, it may be necessary to reschedule these sessions with little notice.
X-ray operator training is available to CEDT members in cases where XRD analysis constitutes an integral aspect of thesis research.
Operators must first attend an x-ray radiation safety seminar provided by McMaster Health Physics, after which a dosimeter is provided.
Specific XRD training on the Bede D1 system can be arranged through the CEDT. Typically, instrument training takes a few hours and requires some subsequent supervision before users become comfortable with independent system operation.