Tuning the electromechanical properties and polarization of Aluminium Nitride by ion beam-induced point defects

We report the evolution of uniaxial strain, resulting in an expansion c-axis wurtzite structure by up to 1 %, without significant degradation crystal 30 keV Zr+ implanted epitaxial AlN films, grown on Si substrates. Raman and X-ray absorption spectroscopies demonstrated that dominant defects are ZrAl, VAl VN. The strain can be attributed a weakening Metal-N π bond along c-axis. Monte Carlo simulations further predict formation cation-rich region within Zr implantation range, with buried anion-rich layer for all investigated fluences. undergoes polarity inversion, which was experimentally confirmed high-resolution high-angle annular dark field scanning transmission electron microscopy. Those microstructural changes influence macroscopic electromechanical properties AlN. effective piezoelectric coefficient, d33, reduces from (7.0 ± 0.5) pm/V (5.2 at fluence 1015 at./cm2 Zr+. At higher fluences strain- compositionally-induced change, coefficient decreases due crystalline damage. These results provide pathway optimise performance ion applications such as energy harvesting, light-emitting diodes acoustic wave devices. In addition, capability engineer polarisation inversion after growth may enable novel device design.