Piezoclectric. Inode atomic force microscope was utilized to characterize a polycrystalline rBi2Ta209 thin fihn. It was found that a hysteresis loop can be obtained using a stiff tip with force constant of 48 N/m. On the other hand, the detected signal using a soft conducting tip with fl～rce constant of 3 N/m increases linearly with the increase Of the applied dc electric field·ln order to identify the types of the measurecl signals. we simulated a case, in which an Ideal piezoelectric hysteresis loop IS overlapped by a Iinear electrostatic signal. It was found that the coercive voltage Of the electrostatic-torce-coupled hysteresis loops decreases with the illcrease of the electrostatic signal. Furthermore, the electrostatic-force-coupled ptezoresponse can not reach a saturated value. This suggests that the signal measured usmg the soft Up IS aft electrostatic predominant signal, whtle the signal detected using the stifftip is a piezoelectric predominant response. [ DOt: 10.1143/JJAP. 41. 67931]