Infrared transmissive and rain-erosion resistant performances of GeC/GaP double-layer thin films on ZnS substrates

► GeC/GaP films were deposited on ZnS substrates and the average transmittance of GeC/GaP/ZnS over 8-11.5 μm rises compared with that of ZnS. ► Rain erosion test was performed and the damage to GeC/GaP and ZnS were discussed. ► Results show that GeC/GaP films can well protect ZnS from rain erosion.