The resistance of BF2+ ion-implanted-polycrystalline diamond film drifted higher with time in air. The drift problem in resistance was eliminated by a temperature-cycling treatment between room temperature and 400-degrees-C under vacuum. The resistance of the temperature-cycled diamond film drifted higher again when the diamond film was exposed in different gas ambients. The effects of H-2, N2, and O2 gas ambients on the resistance of the temperature-cycled diamond film were similar. The resistance drifted higher with time and then reached a saturation value. No saturation plateau was observed for air exposure, which was different from that in H-2, N2, or O2 gas exposure. The increase in resistance was attributed to gas trapped inside implanted polycrystalline diamond films. A passivation layer was suggested to protect diamond films from the drift problem.