Development and environmental stability of ITO thin film for spacecraft application

Abstract

Indium tin oxide films were deposited on flexible fluorinated ethylene propylene substrate by rf magnetron sputtering at room temperature. The effects of different process parameters, such as substrate etching, sputter power density, simultaneous plasma etching and deposition time, were investigated. The functional properties of the film, i.e. transmittance, reflectance, figure of merit, lattice distortion, sheet resistance and its adhesion to the substrate, were studied. The optimised film showed average transmittance of ∼87% (400–900 nm wavelengths) and sheet resistance value of ∼2·54 kΩ □⁻¹. The crystal structure, composition and surface morphology of the film were investigated using X-ray diffraction, energy dispersive X-ray spectroscopy and scanning electron microscopy. Further, the space worthiness of the film was examined by simulated space environments, e.g. humidity, thermal cycling and thermovacuum tests.

Keywords:

• Indium tin oxide
• Flexible optical solar reflector
• rf magnetron sputtering
• Microstructure
• Transmittance
• Reflectance
• Sheet resistance
• Simulated space environment tests

Acknowledgements

The authors are grateful to Professor K. Narasimha Rao, IISc, Bangalore, for providing transmittance and reflectance measurement facility and Dr R. Uma Rani, ISRO Satellite Centre, for useful scientific discussions during the course of this work.