All devices were prepared on silicon-on-insulator (SOI; Soitec Inc.) wafers. The SOI wafers were pre-doped by thermally diffusing spin-on-dopant (Boron A; Filmtronics, Inc.) with rapid thermal annealing (RTA) at 820C for 3 minutes. The resulting sheet resistance indicates a doping concentration of 2x10 19 cm -3 , with the thickness of the silicon epilayer determined by atomic force microscopy to be 25 nm, 22 nm and 20 nm (depending on the device) with a variance of 1 nm. The nanomesh films (NM) and nanowires (NWA) are fabricated by the SNAP technique [30], while the e-beam nanomesh (EBM) and thin films (TF) are defined by e-beam lithography (EBL).For the NM devices, two perpendicularly aligned Pt nanowire arrays are made using two consecutive superlattice nanowire pattern array (SNAP) procedures on top of an SOI wafer (Soitec, Inc.). SNAP protocols are described in Refs. 17 and 30. For the NWA devices only one SNAP procedure is carried out, resulting in a single, aligned Pt nanowire array. For the EBM and TF devices, e-beam lithography and metallization are used to make the transfer-ready Pt nanostructures. Next, we define the membranes

The diameter-dependent Young's modulus, E, and quality factor, Q, of GaN nanowires were measured using electromechanical resonance analysis in a transmission electron microscope. E is close to the theoretical bulk value ( approximately 300 GPa) for a large diameter nanowire (d=84 nm) but is significantly smaller for smaller diameters. At room temperature, Q is as high as 2,800 for d=84 nm, significantly greater than what is obtained from micromachined Si resonators of comparable surface-to-volume ratio. This implies significant advantages of smooth-surfaced GaN nanowire resonators for nanoelectromechanical system (NEMS) applications. Two closely spaced resonances are observed and attributed to the low-symmetry triangular cross section of the nanowires.

High‐resolution transmission electron microscopy (HRTEM) and cross‐sectional transmission electron microscopy (XTEM) are used to characterize common defects in wurtzite GaN nanowires grown via a vapor–liquid–solid (VLS) mechanism. HRTEM shows that these nanowires contain numerous (001) stacking defects interspersed with small cubic GaN regions. Using XTEM, bicrystalline nanowires are discovered with twofold rotational twin axes along their growth directions, and are found to grow along high‐index directions or vicinal to low‐index planes. We propose a defect‐mediated VLS growth model to qualitatively account for the prevalence of these extended defects, and discuss the implications of these defects for nanowire growth kinetics and device behavior.