Piezoelectric response of InN nanostructures grown on c-Al2O3 and Si substrates: Role of oxygen incorporation in improved piezoresponse

Abstract

Materials with high piezoelectric coefficients are crucial in developing high piezopotential nanogenerators. The present study reports the effect of oxygen incorporation in improving the piezoelectric coefficient of InN nanostructures. InN nanostructures are grown on sapphire and Si substrates using the chemical vapor deposition technique. The nanostructures grown on Si substrate have a marginally higher carrier density (∼ 2.6 × 1018 cm−3) compared to that (∼ 1.8 × 1018 cm−3) for nanostructures grown on a sapphire substrate. The piezoresponse of nanostructures is studied using piezoresponse force microscopy (PFM). InN nanostructures grown on Si substrates showed one-order higher piezoresponse than nanostructures grown on a sapphire substrate. The piezoelectric coefficients (d33) are estimated to be 12 and 28 pm/V for the nanostructures grown on sapphire and Si substrates, respectively. The high piezoresponse of nanostructures grown on Si substrate is attributed to the structural instability and chemical heterogeneity induced by O defects.