Extended Data Fig. 2: X-ray diffraction pattern of bulk sample and device S4.

To check the crystalline alignment of the microstructure, we have performed X-ray diffraction measurements on both the bulk single crystal before FIB-fabrication (left) and the micro-structured device (right). The comparison demonstrates no change of crystalline structure. Note that as the substrate around the microstructure becomes a shadow for X-ray at certain angle range, the numbers of diffraction peaks are slightly reduced. The full angle X-ray measurement is accompanied by a video taken by the optical camera which records the motion of rotation in one degree step. We found that the crystallographic c-axis is aligned with the surface norm of the silicon substrate, demonstrating nearly zero misalignment. Based on the accuracy of such determination, the misalignment of crystalline axis is restricted to ± 0.5 degree.