Substrate temperature dependent bolometric properties of TiO2−x films for infrared image sensor applications

In this study, we investigated the substrate temperature (TS) dependent bolometric properties on TiO2−x films for infrared image sensor applications. The film crystallinity was changed from amorphous to rutile phase with increasing the TS. The decrement of resistivity with temperature in TiO2−x test-devices confirms the typical semiconducting property. All the test pattern devices have linear I-V characteristic performance which infers that the ohmic contact was well formed at the interface between the TiO2−x and the Ti electrode. The resistivity, activation energy (Ea) and the temperature coefficient of resistance (TCR) values of the device samples were decreased up to 200 °C of TS. The sample deposited at 200 °C had a significantly low 1/f noise parameter and a high universal bolometric parameter (β). However, at the substrate temperature of 250 °C, the Ea, TCR and the 1/f noise values were increased due to increase of the resistivity. The TCR and the 1/f noise values are proportional to the resistivity of TiO2−x films. As a result, the low resistivity of TiO2−x sample deposited at 200 °C is a viable bolometric material for uncooled IR image sensors.