Evaluation of LSCO Electrodes for Sensor Protection Devices
- PDF / 2,141,463 Bytes
- 6 Pages / 391.5 x 607.5 pts Page_size
- 108 Downloads / 191 Views
ABSTRACT We have evaluated lanthanum strontium cobalt oxide (La 0 .5OSre50COOO; 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 2/sq.). To meet these needs, the effects of postdeposition 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 cm-I and resistivities of- 0.08 to 0.5 f2-cm. With annealing at 800'C, the resistivity decreased to 350 jiQ-cm, while the absorption coefficient increased to 4 - 155,000 cm- . 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. INTRODUCTION "Optical" information, whether obtained by electronic sensors or the vision of an individual soldier or aircraft pilot, is becoming of greater importance in a range of battlefield management scenarios. Because of the increased reliance on optical information, protection of sensor systems is, therefore, also becoming ever more important. At the same time, the threat of damage to these sensors by antagonistic forces is also increasing. While the U.S. and other governments have agreed to prohibit the use of weapons that are designed to cause blinding, the use of tunable lasers by terrorist organizations still poses a significant threat [1]. Thus, devices that provide optical limiting and serve to protect sensor systems are of great importance to the U.S. Military because of the increasing threat of optical "warfare" and the critical need for battlefield intelligence information that is obtained by human sources and electronic sensors. One sensor protection approach is an electrostatic shutter [2] that can be operated at frequencies approaching 100 kHz. A schematic of this shutter, which is currently under development at MCNC [3], is illustrated in Fig. 1. The device is being designed for utilization with sensors that operate in the 3 -5 and 8 - 12 ý.m bands. In the "on" state, the shutter is open (curled) and the underlying sensor device is utilized to gather information. When an optical threat is sensed, through an associated photodiode or similar device, a signal is sent to close the shutter, thus protecting the sensor. The shutter is actuated via an electrostatic mechanism. For the operation of the device, stringent material requirements are placed on the shutter itself as well as the supporting substrate, electrode, and insulating layers. In general, the substrate, electrode and insulator should be as transparent as possible to limit the reduction in the sensitivity of the device, but the electrode must also possess an adequate conductivity to close 365 Mat. Res. Soc. Symp. Proc. Vol. 623 ©2000 Materials Research Soci
Data Loading...