AlN vs. AlScN in Magnetoelectric Sensors

The development of sensors for the detection of weak magnetic fields is of particular interest in biomagnetic diagnostics. A non-invasive detection of magnetic field distribution in the heart, brain or muscles, also known as magnetocardiography (MCG), magnetoencephalgraphy (MEG) and magnetomyography (MMG), can provide a powerful diagnosis of heart, brain or muscle function. State-of-the-art magnetometers for biomagnetic field measurement are ultrahigh sensitive superconducting quantum interference devices (SQUIDs) which require a costly cooling system and a shield room for operation. Therefore, low-cost magnetoelectric (ME) sensors, that possess the ability to detect magnetic fields down to few pico-Tesla at room temperature, are of particular interest. However, the detection limits of ME sensors are not low enough to meet the needs of practical applications, and development work is still in progress. To improve the limit of detection (LOD) of ME sensors, the idea is to increase the sensitivity or reduce the sensor intrinsic noise. In ME sensors, aluminum nitride (AlN) and lead zirconate titanate (PZT) are the most commonly used piezoelectric thin films. It has been recently reported that AlN alloyed with scandium (Sc) significantly enhances its effective piezoelectric coefficient, which is proportional to the sensitivity of ME sensors. Based on this background, the focus of this work is to investigate the influence of the piezoelectric thin films (AlN and AlScN) on the performance of MEMS ME sensors.