Conductive copper sulfide thin films on polyimide foils for optical and optoelectronic applications

Copper sulfide thin films of 75 nm and 100 mn thickness were coated on Kapton foils (PI) of 25 mn thickness by floating them on a chemical bath. The foils were annealed at 150 degreesC-400 degreesC in N-2 converting the coating from CuS to Cu1.8S. The sheet resistance of the annealed coatings (100 nm) is 10-50 ohms/square which is almost unaltered after immersion in dilute HCl for 30-120 min. The infrared reflectance predicted for the coatings is 67%-77% at a wavelength 2.5 mum, which is nearly what is experimentally observed. The coated PI has a transmittance (25-35%) peak located around 550-600 nm. These thermally stable conductive coatings on PI foils might be used as conductive substrates for optoelectronic device structures.