Determination of residual stress in Cr-implanted Al2O3 by glancing angle x-ray diffraction

We report x-ray diffraction measurements of residual stress in sapphire crystals implanted with Cr+ ions. Stress is determined by measuring both in-plane and out-of-plane lattice constants. Bragg peak positions are measured to determine average stress, while peak widths are measured to determine its variation. Using angles of incidence close to the critical angle for total external reflection of x rays, we compare measurements confined to within ∼2.5 nm of the surface and measurements over the ∼80 nm thickness of the implanted region. These x-ray residual stress determinations are consistent with those based on indentation crack length, but were less by a factor of 10 than reports based on cantilever bending