Diameter-Dependent Electromechanical Properties of GaN Nanowires

Abstract

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.

Size-independent Young's modulus of inverted conical GaAs nanowire resonators

“…Experimental nanowire resonance frequencies (black circles) plotted as a function of the geometry factor G and fitted line through origin (solid line), yielding a constant Young's modulus E = (45 ± 3) GPa. The inset shows an enlarged view of the leftmost part of the plot indicated by a black rectangle, clearly demonstrating that the ten most flexible nanowires are equally well-described by the global value of E as their more rigid counterparts exhibiting a larger geometry factor G. Error bars on the G-axis include the uncertainty in determining r, R and h by SEM analysis.A possible explanation for this vast spread could be a dependence of Young's modulus on the geometric dimensions of the underlying nanowires, which is actively discussed in part of the research literature [12][13][14][15][33][34][35][36]. In order to elucidate possible size effects in our data, Young's modulus is additionally determined for each individual nanowire, again using eq.…”

“…A possible explanation for this vast spread could be a dependence of Young's modulus on the geometric dimensions of the underlying nanowires, which is actively discussed in part of the research literature [12][13][14][15][33][34][35][36]. In order to elucidate possible size effects in our data, Young's modulus is additionally determined for each individual nanowire, again using eq.…”

Aspect Ratio Dependence of the Elastic Properties of ZnO Nanobelts

“…8 Conversely, the modulus of GaN nanowires increases with increasing diameter, reaching the bulk value at 84 nm. 9 The origin of the elastic modulus size dependence has been related to different effects such as the presence of defects 9,11 and the balance between surface and bulk properties as the surface-to-volume ratio varies. 10,12 The elastic properties of ZnO nanostructures and their size dependence have been previously investigated by means of transmission electron microscopy (TEM) 10,13,14 and atomic force microscopy (AFM).…”

An open-source platform to study uniaxial stress effects on nanoscale devices

“…11 Because of the competition between atomic coordination and electronic distribution, surfaces can be softer or harder than the bulk. 12 As a consequence, mechanical properties like Young's modulus can be increased 13 or decreased 14 compared with those of bulk crystals by decreasing the nanowire cross section down to the nanoscale. By leveraging this class of phenomena, high values of strain were obtained in semiconducting nanostructures.…”