In this work we present a comparative study on the electrical characteristics of polymorphous silicon (pm-Si:H) and polymorphous germanium (pm-Ge:H) thin films deposited by low frequency plasma enhanced chemical vapor deposition (LF-PECVD), aiming to use them as thermo sensing elements in uncooled microbolometers. We studied th e effect of the deposition pressure on the film characteristics that are important for IR detection, as the activation energy (Ea), the thermal coefficient of resistance (TCR), the room temperature conductivity (σTR) and the film responsivity with IR radiation. Our results indicate that polymorphous films have advantages over boron doped a-Si:H, material which is currently employed as thermo-sensing element in commercial microbolometer arrays.