Multi-layer MgF2/ITO coatings for electromagnetic interference shielding

Indium tin oxide (ITO) coatings have been found useful for diverse applications including electromagnetic interference (EMI) shielding for defense and aerospace purposes, solar cells, gas sensors, etc. However, the reliability, adhesion, transmittance and control of conductivity are some issues that need to be discussed for EMI shielding. Composite multi-layer coating of magnesium di-fluoride (MgF2) and ITO have been deposited on soda lime glass substrate using electron beam (e-beam) deposition technique at a substrate temperature of 350 °C and annealed in the temperature range of 200–500 °C for 1 h under vacuum. The deposited coatings have been characterized for structural, optical and electrical properties. The deposited coatings were crystalline with a crystallite size in the range of 20–30 nm for ITO and 15–20 nm for MgF2 coatings. The coating thickness of ITO and MgF2 determined by Rutherford backscattering technique were found to be 95 nm and 12 nm, respectively. The maximum transmittance in the visible range is ~92% for as-deposited and annealed multi-layer coatings. The band gap has been found in the range of 3.95–4.02 eV, which is suitable for EMI shielding effectiveness. Raman spectroscopy confirms quantum confinement in MgF2/ITO coatings. The electrical conductivity of as-deposited MgF2/ITO coating has been found to be 200 (Ω-cm)−1 which increased to a value of 1.002 x 103 (Ω-cm)−1 for the sample annealed at 500 °C under vacuum. The multi-layer coating annealed at 500 °C show good EMI shielding effectiveness of 50.4 dB without scarifying the transmittance. •High quality multi-layer MgF2/ITO coatings were prepared by e-beam evaporation technique with nanoscale thickness.•The RBS technique confirmed the deposited films thickness.•The Raman spectroscopy results confirm quantum confinements effects in the coatings.•The multi-layer coatings show good transmittance in the visible range with high conductivity.•These coatings reflect EMI shielding effectiveness of 50.4 dB, which can be employed for aerospace & defense applications.