The interface properties between well-polished MCT and ZnS layers deposited by three different physical techniques, and DLC prepared by RFPCVD, have been investigated by AES, IRTS, etc. ZnS and DLC films can prevent the outward diffusion of the components in MCT. However, Zn and S in the ZnS layer tend to diffuse into the MCT, especially, the S diffuses deeper in the case of EBV, and O is detected especially after PLD, but C in the DLC layer diffuses only slightly into the MCT. In particular, the IR transmission of the MCT with deposited DLC is obviously raised, and higher than that of the MCT with deposited ZnS at least in the range of 7.1-7.5 mu m.