We have studied the effect of optical interference on element profiles obtained with a glow discharge optical emission spectrometer (GDS). The specimens were borophosphosilicate glass films deposited on polished silicon wafers. We found that in some cases the interference is accompanied with a beat in the profile: a damping of the sinusoidal wave followed by a recovery. Profilometry showed that the depth resolution is better when the interference continues continuously without a beat. We showed by simulation that the cause of the beat came from variation of the penetration rate throughout the sputtered area.
