Piezoelectricity of Ferroelectret Porous Polyethylene Thin Film

A ferroelectret porous polyethylene (Fp-PE) film with a thickness of 30 mu m and a porosity of 58% was fabricated; its perpendicular piezoelectric constant d(33) was 80 pC/N. In the Fp-PE film observed by atomic force microscopy (AFM), pores with a diameter of about 0.3 mu m were almost homogeneously distributed. Moreover, from piezoresponse force microscopy (PFM), it was found that areas surrounding the pores shift in one direction following the application of ac voltage, but that areas far from the pores cannot move freely. These results indicate that the electrical charges trapped in areas surrounding the pores in the Fp-PE film play an important role in piezoelectricity. (C) 2009 The Japan Society of Applied Physics