Quantized Acoustic-Phonon Modes in Metallic Nanowire Structures

We conducted a detailed theoretical study on quantized acoustic-phone modes in metallic nanowile structures. Cylindrical metallic nanowire (NW) structures realized from the state-of-the-art nanotechnology, were used to demonstrate Ni NW embedded in Al2O3 template. The phonon modes were examined by solving the wave equations with corresponding boundary conditions. We find that the quantized phonon energy and the energy spacing between different phonon states increase with decreasing of NW radius. The allowed phonon modes lie below the straight line of qzVAl2O3 in the dispersion relation, and such a feature does not vary significantly with altering of NW radius. This study will be pertinent to the applications of metallic NW systems as high-frequency ultrasonic devices.