About GIXA

The term Glancing Incidence X-ray analysis was coined by W.W. van den Hoogenhof and D.K.G. de Boer in their paper of the same name ^[1].
They describe 5 types of measurements, which can be realized by controlling the angles of incident and detection:

• Total-reflection X-ray fluorescence spectrometry (TXRF)
• Angle-dependent TXRF (AD-TXRF) also known as Grazing Incidence XRF (GIXRF)
• Reflectivity (XRR)
• Rocking curve
• Glancing-incidence X-ray diffraction

We will focus our description on the first three techniques, which are the main area of our research.

Total Reflection X-ray Fluorescence Analysis

TXRF is an energy dispersive analysis with a special excitation and detection geometry. A narrow almost parallel beam is impinging at angles below the critical angle on the surface of the reflector, which carries the sample material. An energy dispersive detector is placed directly above the sample at 90 degree to the reflector surface. The main advantages of the TXRF setup are the following:

• Due to the total reflection of the incident photons only a very small part of the primary beam penetrates into the sample carrier. This leads to a drastically reduced spectral background contribution, which originates from scattering on the substrate.
• The incident beam is totally reflected from the sample carrier and the sample is excited by both the incident and the reflected beam, which results in a doubled fluorescence intensity.
• The extreme grazing incidence geometry allows placing the detector very close to the sample surface. This results in a large solid angle for the detection of the fluorescence radiation.

Grazing Incidence X-ray Fluorescence Analysis

GIXRF is an extension of TXRF and measures the X-ray fluorescence induced by an X-ray beam incident under various grazing angles. The resulting angle dependent intensity curves are correlated to the depth distribution and mass density of the elements in the sample. GIXRF provides information on contaminations, total implanted or deposited dose and to some extent on the depth distribution of dopants or thickness and density of layers, but is ambiguous with regard to the exact distribution.

X-ray Reflectometry

XRR is an established technique for the characterization of single- and multi-layered thin film structures with layer thicknesses in the nanometer range. XRR spectra are acquired by varying the incident angle in the grazing incidence regime while measuring the specular reflected X-ray beam. The shape of the resulting angle-dependent curve is correlated to changes of the electron density in the sample, but does not provide direct information on the presence or distribution of chemical elements in the sample.

References

1. ^W.W. Van Den Hoogenhof, D.K.G. De Boer, Glancing-incidence X-ray analysis, Spectrochim. Acta Part B At. Spectrosc. 48 (1993) 277–284, DOI:10.1016/0584-8547(93)80034-R