4 research outputs found
2853231.avi
Propagation of the wavefield along the optical axis when there is an 0.3 degree misalignment angle between two MLLs. Astigmatism occured along diagonal directions in two planes near the nominal focal plane
2853219.avi
Propagation of the wavefield along the optical axis when there is no misalignment. The two focal planes can be seen overlap with each other
Measuring Three-Dimensional Strain and Structural Defects in a Single InGaAs Nanowire Using Coherent X‑ray Multiangle Bragg Projection Ptychography
III–As
nanowires are candidates for near-infrared light
emitters and detectors that can be directly integrated onto silicon.
However, nanoscale to microscale variations in structure, composition,
and strain within a given nanowire, as well as variations between
nanowires, pose challenges to correlating microstructure with device
performance. In this work, we utilize coherent nanofocused X-rays
to characterize stacking defects and strain in a single InGaAs nanowire
supported on Si. By reconstructing diffraction patterns from the 21Ì…1Ì…0
Bragg peak, we show that the lattice orientation varies along the
length of the wire, while the strain field along the cross-section
is largely unaffected, leaving the band structure unperturbed. Diffraction
patterns from the 011Ì…0 Bragg peak are reproducibly reconstructed
to create three-dimensional images of stacking defects and associated
lattice strains, revealing sharp planar boundaries between different
crystal phases of wurtzite (WZ) structure that contribute to charge
carrier scattering. Phase retrieval is made possible by developing
multiangle Bragg projection ptychography (maBPP) to accommodate coherent
nanodiffraction patterns measured at arbitrary overlapping positions
at multiple angles about a Bragg peak, eliminating the need for scan
registration at different angles. The penetrating nature of X-ray
radiation, together with the relaxed constraints of maBPP, will enable
the in operando imaging of nanowire devices