Abstract: SiO_2/Ag thin films system is an important part of mirror inscanning radiometer.Failure analysis of the mirror have been performed byhigh resolution Scanning Auger Microprobe (SAM) and Scanning ElectronMicroscope (SEM).Results of SEM Showed that there is a lot of segrega-tion on surface of the failed mirror.We have found that these segregationare mainly Ag and Cu as well as a few of oxides and sulfides by SAM.Auger depth profiles results indicated that atomic diffusion have been occ-urred among SiO_2/Ag/Cu thin films.The diffusion characteristic of atomicAg,Cu and O are discussed.It is suggested that a bad density of SiO_2 thinfilm may be a possible cause of mirror failure.

Key words: Thin film, Radiometer, Mirror, Failure analysis