Pyroelectric single-element and linear-array sensors based on P(VDF/TrFE) thin films

Abstract

Abstract The application of pyroelectric poly(vinylidene fluoride/trifluoroethylene) (P(VDF/TrFE)) copolymer thin films simplifies the manufacture of pyroelectric single-element sensors and, above all, of sensor arrays with high sensitivity, low noise and slight crosstalk. The sensor consists of a self-supporting membrane that is a combination of silicon oxide and silicon nitride. This membrane is made by anisotropic etching on the back of a (100) silicon wafer. Onto the etched wafer a 1–2 μm thin P(VDF/TrFE) film is formed by spin coating. The pyroelectric copolymer is electrically connected by evaporated electrodes. In this way, both single-element sensors and sensor arrays are produced. Single-element sensors built up from P(VDF/TrFE) with a VDF content of 70–80% on an SiO2/Si3N4 membrane achieve a specific detectivity of up to 3.5×108 cm √Hz W−1 at a modulation frequency of 10 Hz and are temperature stable up to at least 55 °C. For linear arrays noise-equivalent power (NEP) values of 4.5 and 12 nW have been measured at chopper frequencies of 40 and 128 Hz, respectively. The average voltage responsivity Rv (500 K) of P(VDF/TrFE) linear arrays is about 110 000 V W−1 at 40 Hz and 40 000 V W−1 at 128 Hz.