Strain mapping in an InGaN/GaN nanowire using a nano-focused x-ray beam

Abstract

Strained InGaN/GaN core-shell nanowires (NWs) are promising candidates for solid state lighting applications due to their superior properties compared to planar films. NW based devices consist of multiple functional layers, which sum up to many hundred nanometers in thickness, that can uniquely be accessed in a non-destructive fashion by hard X-rays. Here, we present a detailed nanoscale strain mapping performed on a single, 400 nm thick and 2 μm long core-shell InGaN/GaN nanowire with an x-ray beam focused down to 100 nm. We observe an inhomogeneous strain distribution caused by the asymmetric strain relaxation in the shell. One side of the InGaN shell was fully strained, whereas the other side and the top part were relaxed. Additionally, tilt and strain gradients were determined at the interface with the substrate.

PtyNAMi: Ptychographic Nano-Analytical Microscope at PETRA III: interferometrically tracking positions for 3D x-ray scanning microscopy using a ball-lens retroreflector

“…26,27,[29][30][31] The instrument served as a test bench for developments of methods and instrumentation in x-ray microscopy, pushing ptychography to high-resolution 15 and sensitivity 32 and combining the technique with resonant scattering to obtain chemical contrast. 33 Ptychography was used to characterize various x-ray optics, including refractive optics like adiabatically focusing lenses (AFL), 34,35 refractive lamellar lenses (RLL), 36 and kinoform lenses, 24 and diffractive optics, such as multilayer Laue lenses (MLL) 22,25 and Fresnel zone plates (FZP).…”

“…Applications for this are reciprocal space mapping, Bragg coherent diffraction imaging, or Bragg ptychography. 26,27 • reducing the scattering background of the instrument by an appropriate flight tube integrating a windowless in-vacuum pixel detector (Eiger X 4M). The new flight-tube system [cf.…”

Bragg coherent diffractive imaging of strain at the nanoscale

“…[14][15][16][17] Especially noticeable is the ability of such techniques to resolve volumetric strain distribution and evolution in individual and extended nanostructures. In scanning X-ray diffraction mapping, the resolution is "beam size" limited, 18,19 while BCDI can provide information about the nanocrystals internal strain, shape, and response functions such as electric polarization 17 with high spatial resolution 20 limited only by the wavelength of X-rays and angular acceptance of the detector.…”

Positional dependence of defect distribution in semipolar hydride vapor phase epitaxy-GaN films grown on patterned sapphire substrates

“…An X-ray microdiffraction (XRMD) system using a synchrotron radiation source is one of the most appropriate characterization tools having a submicrometer-scale X-ray probe to characterize microscopic crystalline properties. [10][11][12][13][14][15] Using a two-dimensional reciprocal lattice space map (2D-RSM) obtained by XRMD analysis, we have recently clarified the microscopic distributions and fluctuations of strain and the lattice plane microstructure in epitaxial nitride semiconductor thick films grown on patterned substrates. 13,14) For example, in ð20 " 21Þ MOVPE-GaN films grown on a ð22 " 43Þ PSS, the results clearly showed that the fluctuation of 20 " 21 lattice plane tilting in the MOVPE-GaN films was strongly affected by the patterning pitch and structure of the PSS.…”

“…15,16) Using this 3D-RSM analysis technique, three-dimensionally microscopic crystalline properties in the nitride semiconductor films grown on PSSs or in the nanowire structures can be characterized with high spatial resolution. In the present study, we investigated the positional dependence of microscopic fluctuations of lattice plane tilting and distributions of crystalline defects (dislocations and BSFs) in semipolar ð20 "…”