Fig. 2: BCDI results for a structure obtained with the 5-µm-side triangular mask and using the y = 0.9% GaAs_1−yN_y epilayer.

a XRD pattern at the peak of the [004] GaAs_1−yN_y rocking curve taken by a 13-µm-pixel size CCD camera. Intensity color map (right side) is in logarithm scale given as power of 10. b Reconstruction of the amplitude of the complex density function giving the 3D shape of the fabricated microstructure; the two renderings use isosurfaces equal to 50% of the amplitude maximum. The reconstructed triangle looks flat since the thickness of the original GaAs_1−yN_y epilayer (200 nm) is much smaller than the object lateral dimensions. Resolution of the reconstructed image is about 85 nm, pixel size is 51 nm. c Reconstruction of the phase of the complex density function, producing a 3D map of the out-of-plane atom displacement; the phase is represented by the phase values that intersect the amplitude isosurface obtained at 50% of the amplitude maximum. The color scale has radians units, phase zero corresponding to the strain level of the GaAs_1−yN_y alloy pseudomorphically grown on the GaAs substrate. d Reconstruction of the out-of-plane strain (ε_zz) calculated as the gradient of the out-of-plane atom displacement field (u_z) along the momentum transfer direction; the strain is represented by the strain values that intersect the amplitude isosurface obtained at 50% of the amplitude maximum, the color scale is in percent. The displacement u_z is related to the phase Φ_z through the relation Φ_z = 4 × (2π/a_z^GaAsN) × u_z, where a_z^GaAsN is the out-of-plane lattice parameter of GaAs_1−yN_y. In the Cartesian axis representation “z” indicates the vertical direction, “y” the direction of the x-ray beam, “x” the direction transverse to the beam; the same representation is used in all figures. The full 3D reconstructed complex density function is available upon request from the authors as a Matlab data file.