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

Superscrew dislocations arc visible in back-reflection synchrotron while-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 white-beam 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 CuKα₁ 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.