Pyroelectric linear array infrared sensors made of c-axis-oriented La-modified PbTiO3 thin films

Abstract

High sensitive pyroelectric linear array infrared sensors have been fabricated by using highly c-axis-oriented and spontaneous polarized La-modified PbTiO3 (PLT) thin films. The PLT thin films were deposited on (100)-oriented Pt thin film on (100)-cleaved MgO single crystals by rf magnetron sputtering. The PLT thin films have high figures of merit for voltage responsivity (Rv) and specific detectivity (D*) without a poling treatment. Two types of linear array sensors, reticulated and nonreticulated ones, were fabricated. The reticulated and nonreticulated sensors have 64 elements with 200-μm pitch and 128 elements with 100-μm pitch, respectively. Ni-Cr electrodes of approximate area 1.9×10−4 or 3.0×10−4 cm2 were deposited by vacuum evaporation on the PLT thin films with a thickness of 3–4 μm. Pyroelectric coefficients and their uniformity increased upon decreasing the deposition area of an element. Therefore, the elements of reticulated sensors have considerably larger Rv and D* compared with the nonreticulated ones. The nonreticulated sensors have a very high resolution of 10 elements/mm, a large Rv of 900 V/W at 100 Hz, and a high D* (500 K, 100, 1) of 1.5×108 cm Hz1/2/W. Furthermore, the reticulated ones have a very large Rv of 2200 V/W, a remarkably high D* of 6×108 cm Hz1/2/W, and a very low thermal cross talk of <3% at 100 Hz.