Development Of Transparent Lsco and Lscno Conductors for Optical Shutter Systems

ABSTRACTWe have prepared lanthanum strontium cobalt oxide (La0.50Sr0.50CoO3; LSCO 50/50) and lanthanum strontium cobalt nickel oxide (La0.50Sr0.50Co0.50Ni0.50O3; LSCNO) as candidate transparent electrodes for use in a shutter-based infrared sensor protection device. The shutter device requires that the electrode be transparent (80% transmission) and have moderate sheet resistance (300 ω/sq.). Because of the effects of film thickness on intrinsic material properties, such as resistivity and extinction coefficient, and simple engineering issues (i.e., the relationship between film thickness, resistance and transmission), films of various thicknesses were prepared to achieve an optimal balance of electrical and optical performance. van der Pauw measurements and FTIR spectroscopy were used to study thin film properties. The best LSCO films prepared demonstrated electrical (438 ω/sq.) and optical (68% transmission at 8 µm) properties that did not meet the target property goals for this application. However, the LSCNO films (of optimal thickness) offered performance (323 µ/sq. and 73% transmission) close to the device requirements.

Evaluation of LSCO Electrodes for Sensor Protection Devices

We have evaluated lanthanum strontium cobalt oxide (La0.5OSr0.50COOx; LSCO 50/50) as a candidate “transparent” electrode for use in an electrostatic shutter-based infrared sensor protection device. The device requires that the electrode be transparent (80% transmission) and have moderate sheet resistance (300 – 500 Δ/sq.). To meet these needs, the effects of post-deposition annealing on the resistivity and optical absorption characteristics of sputter deposited LSCO thin films were studied. The as-deposited films were characterized by an absorption coefficient of ∼ 12,500 cm1−1 and resistivities of ∼ 0.08 to 0.5 Δ-cm. With annealing at 800°C, the resistivity decreased to 350 νΔ-cm, while the absorption coefficient increased to ∼ 155,000 cm1−1. By using a post-deposition annealing step at 800°C and controlling film thickness, it appears that a standard LSCO 50/50 material may possess the requisite conductivity and optical transmission properties for this sensor protection device.