Nanocrystalline Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> (BTO) thin film pressure sensor was fabricated by sol gel method. The multiple Bi-Ti-O layers were spin coated over the TiO<sub>2</sub> buffered Si/SiO<sub>2</sub>/RuO<sub>2</sub> substrate, followed by heating of each layer at 300 °C for 15 mins. The nanocrystalline Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> film was formed after the sample was rapid thermal annealed at 450 °C in air for 60 s. The scanning electron microscope result showed that the film exhibited crack free, fine and uniform grain structure, where the grain size obtained was around 10 to 15 nm. For the sensor response measurement, Al film was deposited as top electrode and the sensor tested by pneumatic loading method. The nanocrystalline Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> (BTO) thin film demonstrated good repeatability for the pressure sensing. The sensor achieved a linear characteristic response between 17.5 psi and 65 psi with sensitivity of 0.3 mV / psi.
Polycrystalline Bi-Ti-O thin films were prepared by multilayer deposition method using electron beam evaporation. The thin films were obtained by sequentially evaporating Bi<sub>2</sub>O<sub>3</sub> / TiO<sub>2</sub> layers on Si / SiO<sub>2</sub> substrate followed by a heat treatment for 2 hours in air at 900 °C. The piezoelectric response of the sample was measured by pneumatic loading method. A pressure sensor was fabricated by annealed the deposited multilayer thin films on Si / SiO<sub>2</sub> /Au substrate and Al was then deposited as top electrode. When an air pressure was applied and imparted on the sensor, electrical voltage was generated and measured using an electrometer. The sensor’s response was measured at three response cycles. It was found that the sensor has good voltage sensitivity and repeatability. The study shows the possibility to obtain Bi-Ti-O
thin film pressure sensor by electron beam multilayer deposition.