NanoMAX is a hard x-ray nanoimaging beamline at the new Swedish synchrotron radiation source MAX IV that became operational in 2016. Being a beamline dedicated to x-ray nanoimaging in both 2D and 3D, NanoMAX is the first to take full advantage of MAX IVs exceptional low emittance and resulting coherent properties. We present results from the first experiments at NanoMAX that took place in December 2016. These did not use the final experimental stations that will become available to users, but a temporary arrangement including zone plate and order-sorting aperture stages and a piezo-driven sample scanner. We used zone plates with outermost zone widths of 100 nm and 30 nm and performed experiments at 8 keV photon energy for x-ray absorption and fluorescence imaging and ptychography. Moreover, we investigated stability and coherence with a Ronchi test method. Despite the rather simple setup, we could demonstrate spatial resolution below 50 nm after only a few hours of beamtime. The results showed that the beamline is working as expected and experiments approaching the 10 nm resolution level or below should be possible in the future.
The core-shell nanowires have the promise to become the future building blocks of light emitting diodes, solar cells and quantum computers. The high surface to volume ratio allows efficient elastic strain relaxation, making it possible to combine a wider range of materials into the heterostructures as compared to the traditional, planar geometry. As a result, the strain fields appear in both the core and the shell of the nanowires, which can affect the device properties. The hard x-ray nanoprobe is a tool that enables a nondestructive mapping of the strain and tilt distributions where other techniques cannot be applied. By measuring the positions of the Bragg peaks for each point on the sample we can evaluate the values of local tilt and strain. In this paper we demonstrate the detailed strain mapping of the strained InGaN/GaN core-shell nanowire. We observe an asymmetric strain distribution in the GaN core caused by an uneven shell relaxation. Additionally, we analyzed the local micro-tilt distribution, which shows the edge effects at the top and bottom of the nanowire. The measurements were compared to the finite element modelling and show a good agreement.
X-ray Bragg ptychography (XBP) is an experimental technique for high-resolution strain mapping in a single nano- and mesoscopic crystalline structures. In this work we discuss the conditions that allow direct interpretation of the ptychographic reconstructions in terms of the strain distribution obtained from the two dimensional (2D) XBP. Simulations of the 2D XBP experiments under realistic experimental conditions are performed with a model of InGaN/GaN core-shell nanowire with low (1%) and high (30%) Indium concentrations in the shell.