CHARACTERIZATION OF THIN SURFACE-LAYERS BY AN X-RAY DOUBLE-CRYSTAL METHOD WITH A SAMPLE DESIGNATED AS THE 1ST CRYSTAL

It is shown that thin surface layers can be sensitively characterized by using an X-ray double-crystal method, in which a sample designated as the first crystal is irradiated with incident X-rays at a low glancing angle and the X-rays reflected from the surface layer are analyzed by a second crystal. The applicability is proved by observing GaAs crystals lapped with fine abrasives. Deviation of the full width at half-maximum (FWHM) of the rocking curve for lapped crystals from that of a perfect crystal is a few times larger than the value obtained by the conventional method in which the sample is the second crystal.