Phase identification in thin films
Grazing incidence thin film analysis
Phase identification in thin films and surfaces refers to a diffraction technique that enhances the weak diffracted signal which originates from a small diffracted volume of a thin film, or near-surface area, during analysis. It is often referred to as grazing incidence X-ray diffraction. Thin film phase identification is applied to characterize randomly oriented or weakly textured polycrystalline thin films. In a GIXRD measurement, the angle of incidence of the X-rays with respect to the sample surface is kept fixed at a low value. This value is typically chosen close to the critical angle of total external reflection. This ensures a reduced penetration of the X-rays into the sample and an increase in the path length through a thin film. GIXRD measurements performed in a parallel beam geometry are less sensitive to sample height displacement.
Benefits of grazing incidence angle thin film analysis
- Confinement of most or all of the incident X-ray beam within the thin film, since the penetration depth is significantly reduced due to the low angle of incidence of the X-rays. This helps to increase the diffracted intensity of the film with respect to the background.
- Reduction in the intensity of the diffracted signal from the substrate. Complete suppression is possible for single crystal substrates.
- Depth control that contributes to the diffracted information by changing the angle of incidence of the X-rays.
Solutions for thin film analysis
GIXRD experiments can be performed on PANalytical's X'Pert³ MRD (XL), Empyrean or X’Pert³ Powder systems. PANalytical’s PreFIX stage interface enables parabolic X-ray mirrors to be placed quickly and accurately in the X-ray optical path to deliver the highest intensity and best performance with no need to realign the system.
Diffraction data can be analyzed using a selection of either automatic or manual procedures implemented in the HighScore software package. Qualitative and quantitative phase analysis and crystallite size determination can be performed in HighScore (Plus).
Using the Stress Plus software package, GIXRD measurements can also be used to perform residual stress measurements in thin films and coatings. The grazing incidence angle geometry is also applied in the thin film applications reflectometry and in-plane diffraction.