Poly(vinylidene fluoride) (PVDF) is a semi-crystalline polymer, which indicates four different crystalline forms. In this paper, the preparation of nanoscale PVDF thin film was introduced in detail. Initially PVDF was dissolved in the N,N-dimethyl Formamide and acetone mixed solution (volume ratio 1:1). The PVDF films were prepared by spin coating method with different solution concentration, then were characterized by SEM, XRD and FTIR after annealed at different annealing temperatures (60 centigrade to 120 centigrade). Due to the formation of polarized β crystal phase in the annealing process, the pyroelectric coefficient p would be affected by different annealing temperatures. The thermal poling technique of PVDF was also shown in this paper. We investigated the polarization behavior of PVDF when they were subjected to different poling electric fields (from 50 V/μm to 80 V/μm) and poling temperatures (from 90 centigrade to 120 centigrade). For a long enough poling time, the polarization is only related to poling electric filed, while poling temperature affects the poling rate merely. Under the condition of PVDF thin film beforet breakdown, the strongger the poling electric filed intensity, the higher the pyroelectric coefficient is. The pyroelectric coefficient of fibricated PVDF film is 9.0×10-10C/cm2K after 80v/μm electric field intensity polarization from experiment result.
The metamaterial absorber in terahertz (THz) region, with the metal pattern layer/dielectric spacer/metal reflective layer sandwich structure, is characterized in this paper. The principle of metamaterial absorber absorbing terahertz wave was introduced firstly. The top layer of metamaterial absorber is a periodically patterned with metallic subwavelength structure, which also serves as an electric resonator. The bottom layer is a thick metal plane, which is used to reduce THz wave transmittance. The dielectric layer between two metallic layers results in magnetic resonance and the resonance depends on the thickness and dielectric constant of the dielectric layer. The absorption of metamaterial absorber to terahertz wave was simulated with CST software. The relationship between the size of the metamaterial structure and absorption frequency was analyzed with the simulation results. The results indicate that the absorption frequency is affected by the cell constant and geometric structure of top metal pattern, and absorption rate is related to both the thickness of dielectric layer and the size of resonator. In the end, the possibility of integrating the metamaterial absorber with micro-bridge structure to design room temperature terahertz detector was discussed, and the manufacturing process was introduced about room temperature terahertz detector with high THz wave absorption rate.