Electrically Conductive Metal Silicides and Ceramics for EMI/RFI Shielding of IR Windows

Current IR systems are extremely susceptible to electromagnetic and radio frequency interference (EMI/RFI) because they possess large apertures that present ideal front-door entry paths for EM radiation. Significant amounts of EM radiation (400 MHz - 18 GHz) can penetrate and couple to the IR sensor and supporting electronics, which leads to a substantial degradation in systems performance. EMI protection is critical to the survivability of the IR system and the system host (e.g., aircraft, satellite). Conductive metal mesh coatings on external surfaces of IR windows reduce the EM/RF signal but are mechanically soft and easily damaged. Surface doped semiconductors, such as gallium arsenide, have optical absorption and emission problems, while semiconducting carbide coatings, such as germanium carbide, suffer performance loss at the low end of the required temperature range. QUEST Integrated, Inc. will investigate electrically conductive metal silicides and ceramics as erosion resistant EMI/RFI protective coatings for IR windows and radomes. We will deposit selected materials as continuous film and as various mesh pattern coatings by RF plasma sputtering and study their shielding capability and IR optical transparency.