In the present study, we examine the thermal stability of TiO2-x (TiO) and Nb:TiO2-x (TNO) films at different exposing temperatures for the as-deposited and oxygen-atmosphere annealed samples. In order to attain the good thermal stability characteristics, lower resistance of the TiO and TNO samples were annealed in oxygen gas atmosphere at a high flow rate (5 lit/min) of oxygen gas and annealing time (25 min). From the structural studies, it can be confirmed that the annealing process gives the incorporation of oxygen atoms to its vacant sites and the phase transition improvement from the amorphous to rutile structure. The annealed samples reveal the high resistivity and temperature coefficient of resistance (TCR) values than as-deposited samples. Furthermore, it was confirmed that the annealed samples exhibits a significant improvement of thermal stability compared to the as-deposited samples. As a result, the annealed TNO sample exhibits outstanding thermal stability as well as better bolometric performance. Consequently, this study reveals that the annealed TNO sample is appropriate for shutter-less infrared image sensor devices.