Enhanced infrared absorption by ferroelectric-conducting oxide thin-film structures

Infrared absorbing free-standing bridge structures are anticipated to be used in the next generation of ferroelectric uncooled infrared detectors. These structures will consist of resonant cavities with an absorbing bridge element, which contains the ferroelectric detector and the contact electrodes. An oxide electrode is preferable to a metallic electrode, because the metallic electrode reflects too much of the incoming radiation at reasonable thickness. For this paper, spectral transmission and reflection of lanthanum nickelate (LNO), barium ruthenate (BRO) and strontium ruthenate (SRO) films were measured, and it was found that the properties could be described as a simple two-dimensional conducting sheet. The optical absorption of several freestanding bridge structures was modeled, and optimized dimensions and electrode conductivity are presented which yield greater than 80% absorption over the full 8-14 mum band.