Thickness-dependent leakage current of (PVDF/PbTiO3) pyroelectric bilayer thin film detectors

The novel pyroelectric infrared (IR) detectors have been fabricated using the Polyvinylidene Fluoride (PVDF)/Lead Titanate (PT) pyroelectric bilayer thin films which were deposited onto Pt(111)/SiO₂/Si(100) substrates by a sol-gel process. The ceramic/polymer structure was constructed of the randomly oriented polycrystalline PT film(∼1 μm) heated at 700°C for 1 h and the β-phase PVDF film crystallized at 65°C for 2 h. The effects of PVDF thin film thickness (100∼580 nm) on the pyroelectric response of IR detectors were studied. The results show that the depositions of PVDF thin films onto the PT films will cause the leakage current (J) of the detectors decrease from 6.37 × 10^-7 A/cm² to 3.86 × 10^-7 A/cm². The specific detectivity (D*) measured at 100 Hz decreased from 2.72 × 10^-7 cm·Hz¹2//W for detector without PVDF to 1.71 × 10^-7 cm·Hz¹2//W for detector with PVDF thickness of 580 nm. By optimizing the ratio of the specific detectivity (D*) to leakage current, D*/J, the detector with PVDF thickness of 295 nm exhibits the best performance.