The Study of (Polyvinylidene Fluoride / Lead Titanate) Pyroelectric Bilayer Thin Film Detectors
The pyroelectric ceramic thin films and detectors based on PbTiO3[abbreviated to PT] that exhibit a low dielectric constant and a high pyroelectric coefficient, which were fabricated by a sol-gel method in this thesis. The (PVDF/PT) pyroelectric bilayer thin films with low leakage current were deposited on PbTiO3/Pt/SiO2/Si substrates by the spin coating. 1,3 propanediol was used as solvent to minimize the number of cycles of the spin coating and drying processes to obtain the desired thickness of PbTiO3 thin film. By changing the concentrations of PVDF solutions (0.6M~1.0M) and thickness of PVDF thin films (50nm~580nm), the effects of various processing parameters on the bilayer thin films growth and the response of pyroelectric infrared detector device are studied.
Experimental results reveal that the thickness of PVDF thin films will influence strongly on dielectricity, ferroelectricity, leakage current and pyroelectricity of (PVDF/PT) bilayer thin films. With the increase of the thickness of PVDF thin films, the relative dielectric constant of (PVDF/PT) bilayer thin films decrease from 63 to 20. The tan£_ increases from 0.00152 to 0.0024, leakage current decreases from 1.54x10-6 A/cm2 to 3.86x10-7 A/cm2, Ec decreases from 70.7 KV/cm to 35 KV/cm, Pr decreases from 6.29 £gC/cm2 to 1.14 £gC/cm2, and £^ decreases from 22.5x10-9 C/cm2K to 6.8 x10-9 C/cm2K with an increase of the thickness of PVDF thin film. In addition, the results also show that the largest figure of merit Fv is 1.31x10-10 Ccm/J as the thickness of PVDF thin film is 80nm. With the increase of the thickness of PVDF thin film, the figure of merit Fm decreases from 2.26x10-8 Ccm/J to 1.07x10-8 Ccm/J. The voltage responsivities (Rv) measured at 20 Hz decrease from 1383 V/W to 804 V/W and the specific detectivities (D*) measured at 100Hz decrease from 2.72x107 cmHz1/2/W to 1.71x107 cmHz1/2/W. From the result of D*/J, the result shows the device possesses the best property as the thickness of the PVDF thin film is 165nm. Therefore, the (PVDF/PT) bilayer thin film with the thickness 165nm of PVDF thin film is the most suitable for the applications of pyroelectric thin film IR detectors.
Advisor:Ying-Chung Chen; Houng-Mo Duh; Man-Phon Houng; Nan-Chung Wu; Jung-Chuan Chou
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:pyroelectric lead titanate pvdf thin films detectors sol gel
Date of Publication:07/05/2001