Test devices of unpassivated, single-layer passivated, and double-layer passivated samples were fabricated to analyze the enhancement of thermal stability for shutter-less infrared (IR) image sensors. In this study, double-layer passivation (SiOx/SiNx) was proposed to avoid the oxygen-diffusion from unpassivated or single-layer (SiOx) passivated Nb:TiO2-x (TNO) samples. Before fabricating the test device, high-temperature (450 degrees C) annealing was carried out under oxygen-rich ambient conditions to improve the thermal stability by reducing the number of oxygen vacancies in the as-deposited TNO samples. The double-layer passivated sample showed higher thermal stability than the other samples. The structural and bolometric properties were also studied for all passivated samples and the obtained results attested that the properties seemed to be almost similar for different passivation layers. It was found that the proposed double-layer passivated TNO sample could provide enhanced thermal stability for future shutter-less IR sensors.