Microbolometers on Flexible Substrates
The proposed research focuses on developing “smart” thin film transistor (TFT)-integrated infrared (IR) microbolometer detectors using semiconducting YBaCuO (YBCO) on silicon wafers and in the second phase, on a flexible polymer substrate, Kapton®. This approach will combine the high IR sensitivity of YBCO with the low-temperature fabricated TFT and the flexible substrate. We plan to produce bolometers in small geometries that allows for a better spatial resolution as well as high roll-off frequency leading to high operating frequencies. Nanolithography is needed to achieve sufficiently small pattern resolution. The bolometers will operate at room temperature. The IR sensitive material YBCO has a relatively high Temperature Coefficient of Resistance (TCR) at room temperature compared to its counterparts. The TFT array can be fabricated at low temperatures on a silicon or a flexible substrate such as polyimide.
As a part of this work, the quality of the bolometer sensitive film will be investigated and enhanced by means of fundamental materials science research. YBCO large grained and textured polycrystalline thin films will be produced by the PVD technique, and be used for structural evaluations. The material characterization will involve TCR, electrical noise and optical absorption with different structures, geometries and thicknesses. Based upon these measurements, the film quality will be optimized.
Infrared detectors maintain a wide spectrum of applications. In astronomy, IR observation of space, global movements of clouds, environmental pollution control; in the military field, air-to-air missiles, satellite-borne intercontinental ballistic missile detection systems, night vision, and land mine detection systems are some of the current applications as well as guided land-to-air missiles. Law enforcement units also utilize these detectors against illegal presence and movements in unsecured regions. The proposed nanolithography approach promises higher resolution and higher operating frequencies.