Materials Selection for Micro/Nanoscale Phononic Crystals with Wide Bandgaps

The goal of this work is to determine the widest bandgaps possible for Phononic Crystals (PnCs) operating in the MHz–GHz frequency range by using the Planes Approximation Method (PAM). MHz–GHz PnCs have micro/nanoscale features which must be fabricated in a cleanroom with cleanroom compatible materials. 1D and 2D simulations are performed, using PAM, for bimaterial (two-material) phononic crystals for 41 cleanroom compatible materials to determine the widest bandgaps. 1D results yield a monotonic, characteristic curve demonstrating a logarithmic relationship between the gap/midgap ratio and normalized impedance with an R² value of 0.965. 2D simulations with circular inclusions on a square lattice demonstrate an increasing linear trend for the gap/midgap ratio and normalized impedance. The interplay between the \(\Gamma {\text{X}}\) $\mathrm{\Gamma }\text{X}$ and \(\Gamma {\text{M}}\) $\mathrm{\Gamma }\text{M}$ directions cause deviations from monotonicity.