X-RAY DIFFRACTION A N A L Y S I S OF THIN CLAY FILMS FROM DILUTE SUSPENSIONS USING G L A N C I N G INCIDENCE DIFFRACTION
-X-ray diffraction (XRD) analysis of small quantities of clay mounted on glass slides using conventional Bragg-Brentano geometry generally produces unsatisfactory low-intensity reflections masked by amorphous substrate scatter. Glancing-incidence asymmetric Bragg diffraction, an alternative uncoupled geometry, uses a fixed low-incidence angle and parallel-beam optics to increase path length through the sample and decrease X-ray penetration into the substrate. To evaluate this technique on thin soil clay films, results from conventional Bragg-Brentano and glancing-incidence diffraction (GID) were compared for progressively diluted clay suspensions separated from 2 southeastern soils with typical mineral assemblages. Patterns produced by GID showed overall higher reflection intensities and reduced substrate scatter, especially at higher 20 angles within the amorphous glass region, Using GID, positive identification of clay minerals was obtained from sample quantities as small as 0.005 mg cm 2 and suspensions as dilute as 29 mg L 1. Key Words--GID, Thin Films, XRD.
Method of measurement and analysis of texture in thin films
A method of measurement and analysis of texture in thin films is proposed. In this method, the incidence angle of the X-ray beam is low and is kept constant during the measurements. This requirement allows information to be obtained from a thin surface layer of the specimen. However, it limits the area on the pole figure from which data can be measured. Quantitative analysis of various factors and parameters which affect the X-ray penetration depth and the measured area of the pole figure is proposed. The proposed method was implemented and tested and the results obtained were used to calculate the crystal orientation distribution function.
Differential-mode grazing-incidence diffraction from nanometre-layer heterostructures
The differential mode of the grazing-incidence diffraction is employed for the characterization of a thin Ga1-xAlxAs/GaAs (001) heterostructure. Using a high resolution detector system a conventional X-ray source is appropriate to record the fine structure of the diffraction curve. The quality of experimental curves permits the authors to detect the thickness of both the nondiffracting top part and the perfect crystalline portion of the layer. Their quantitative determination results from simulation of the curve by means of the dynamical and the kinematic theory. Both yield nearly the same crystalline thickness; however, they differ somewhat for the top part. A quantitative interpretation of the real structure of sample is impossible due to the limited experimental resolution.