Preparation of Oriented Aluminum Nitride Thin Films on Polyimide Films and Piezoelectric Response with High Thermal Stability and Flexibility

Abstract

Abstractc‐Axis oriented aluminum nitride (AlN) thin films are successfully prepared on amorphous polyimide films by radiofrequency magnetron reactive sputtering at room temperature. Structural analysis shows that the AlN films have a wurtzite structure and consist of c‐axis oriented columnar grains about 100 nm wide. The full width at half maximum of the X‐ray diffraction rocking curves and piezoelectric coefficient d33 of the AlN films are 8.3° and 0.56 pC N–1, respectively. The AlN films exhibit a piezoelectric response over a wide temperature range, from –196 to 300 °C, and can measure pressure within a wide range, from pulse waves of hundreds of pascals to 40 MPa. Moreover, the sensitivity of the AlN films increases with the number of times it was folded, suggesting that we can control the sensitivity of the AlN films by changing the geometric form. These results were achieved by a combination of preparing the oriented AlN thin films on polyimide films, and sandwiching the AlN and polymer films between top and bottom electrodes, such as Pt/AlN/polyimide/Pt. They are thin (less than 10 μm), self powered, adaptable to complex contours, and available in a variety of configurations. Although AlN is a piezoelectric ceramic, the AlN films are flexible and excellent in mechanical shock resistance.

Ceramics, Electronic

“…AlN-polyimide composites may be a suitable compromise and research in this field is being conducted [28].…”

Mg doping and native N vacancy effect on electronic and transport properties of AlN nanowires

“…AlN is also desirable for its chemical and thermal stability and mechanical strength, which enables its devices to be operated under a large variety of environments [10,11]. Furthermore, its wide band gap and adjustable band offsets are an attractive feature for devices relying on quantum confinement and tunneling transport [12,13].…”

Growth ofc-axis-oriented aluminum nitride thin films onto different substrates and buffer layers

“…AlN thin films grown onto silicon substrates by reactive sputtering have been the common choice, as they are fairly easily deposited with the desired (001) orientation, with growth conditions compatible with standard integrated circuit technology. There is also a growing interest regarding AlN‐based MEMS on amorphous and flexible insulating substrates . While the growth onto amorphous materials such as SiO 2 have been studied in order to obtain low drift composite resonators for oscillators or for sensors based on shear modes, the growth onto flexible polyimides is still a technological challenge.…”