Harmonic composition of synchrotron white-beam X-ray topographic back-reflection images of basal-cut silicon carbide single-crystal wafers

Superscrew dislocations are visible in back-reflection synchrotron white-beam X-ray topographs of basal-cut SiC wafers in striking contrast as black rings surrounding white circles, even though such topographs suffer from extensive harmonic contamination. The contributions to the synchrotron whitebeam topograph of each member of its series of harmonic reflections, g = (0006n), where n = 3 to 16, were calculated. Through intensity considerations and comparison with a g = 00018 topograph taken with Cu K alpha(1) radiation, the g = 00024 harmonic was determined to be the most important contributor. The contrast of features lying deep beneath the crystal's surface was attributed to higher harmonics with larger penetration depths.