C-axis tilted AlN films for vibration energy harvesters

In this study, we reported on the sputtering growth of the c-axis tilted AlN films, which may have higher electromechanical coupling coefficient k3i than [0001]-oriented AlN, on the Si (100) substrates in the aim of high output power vibrational energy harvesters (VEHs). We implemented the incident angle deposition in a wide range of temperature from room temperature (RT) to 650°C. At 420°C the c-axis tilted 22°, which is the largest tilt angle reported for the AlN films grown by incident angle deposition. In addition, by changing growth temperature, we succeeded in preparing c-axis tilted AlN films with different tilt angle. Scanning electron spectroscopy (SEM) revealed that the c-axis tilted films have tilted columnar structures which prevents cracks and pinholes going straight through the films. This feature may help avoiding electrical short between electrodes fabricated on top and bottom of the AlN films in VEHs.