# Influence of Contacts and Applied Voltage on a Structure of a Single GaN Nanowire
## 3 Results  
### Free-Lying Nanowires  
First, we have investigated a series of free-lying NWs without contacting electrodes. The 3D distribution of coherently scattered intensity in the vicinity of a 10\(\bar{1}\)0 GaN Bragg peak of the free-lying NWs in the laboratory frame is shown in Figure 4. The intensity distribution of a free-lying NW of 350 nm in size is presented in Figure 4a,b and demonstrates  
Figure 3: The experimental setup showing the incoming and diffracted beams with the wave vectors \(\mathbf{K}_{0}\) and \(\mathbf{K}_{H}\) and a reciprocal lattice vector \(\mathbf{H}_{10\bar{1}0}\) of the NW that is perpendicular to the Si substrate. The sample is rotated around the Bragg angle \(\theta_{B}\) of 10\(\bar{1}\)0 GaN reflection. The rectangular coordinate system has z-axis perpendicular to the substrate, x-axis along, and y-axis perpendicular to the NW. In the inset, the intensity distribution of a typical free-lying NW recorded by a 2D detector is shown.  
well pronounced hexagonal symmetry with the fringes originating from the opposite facets of the NW. There is only a single star-shaped Bragg peak distribution in reciprocal space (see Figure 4b), which indicates that this NW does not have a significant structural change and may be considered as a deformation-free NW. Several other investigated free-lying NWs of the same size demonstrated similar structure of the Bragg peak distribution in reciprocal space (see Supplementary Materials).  
Further, a single, free-lying GaN NW with a smaller diameter of 200 nm was studied. Its intensity distribution is shown from two different directions in Figure 4c,d. Interestingly,  
Figure 4: The intensity distribution around 10��̄ GaN Bragg reflection of free-lying GaN NWs shown from two different views to emphasize the diffraction pattern details. (**a–d**) Single GaN NWs with the diameters of 350 nm (**a,b**) and 200 nm (**c,d**). The thinner 200 nm NW reveals a double Bragg peak structure due to its bending on the substrate (see text for details). (**e,f**) For a comparison, the intensity distribution of two NWs with the diameters of 350 nm lying close to each other form well separated Bragg peaks in reciprocal space. To enhance the diffraction pattern details, the intensity distributions are represented by two different iso-surfaces. The length of coordinate arrows corresponds to 0.1 nm\({}^{-1}\). The intensity is normalized to the maximum and the iso-surface values are \(10^{-3}\) and \(10^{-4.5}\) (**a,b**), \(10^{-5.0}\) and \(10^{-1}\) (**c,d**), \(10^{-5.0}\) and \(10^{-1}\) (**e,f**).  
the diffraction pattern reveals the \"double-star\" structure of the Bragg peak distribution (see Figure 4d). Two additionally studied 200 nm free-lying GaN NWs demonstrated similar double structure of the Bragg peak intensity distribution (see Supplementary Materials), which is due to the bending of the NWs [22].  
For comparison, a diffraction pattern of 10\(\bar{1}\)0 GaN Bragg peak of two close lying NWs with diameters of 350 nm is presented in Figure 4e,f. In this case of 350 nm thick NWs, two well-separated hexagonal-star Bragg peaks are distinguishable in reciprocal space.  
Therefore, it is possible to conclude that the free-lying GaN NWs with the diameter of 200 nm are already bent in contrast to 350 nm in diameter NWs. This effect makes investigation of the NWs with the diameters smaller than 350 nm more complicated.