DEPTH ANALYSIS OF METAL COATINGS BY GLOW-DISCHARGE SPECTROSCOPY WITH EMPHASIS ON THE INTERFACE PROBLEM

Grimm glow discharge spectrometry was used to analyze metal coatings on various metal substrates to determine the sputter broadening characteristics of the glow discharge lamp, especially at the interface. The sputter broadening characteristics are important when the depth profile is to be found. The samples of Cu/Ni, Ni/Cu, Sn/Ni, Ni/Sn, Fe/Ni, Ni/Fe metal coatings investigated, indicate that the poor depth resolution of glow discharge spectrometry is due to uneven profiling since the central portion of the sputtered surface is sputtered away faster than the edges. This depth resolution problem is fundamentally different from that of depth profiling in AES or SIMS. Besides being dependent on the usual sputtering parameters the depth profile is also dependent on the glow discharge characteristics of the coating metal and substrate metal combination. From the plots of plasma composition vs. fraction of metal coating sputtered, plasma composition vs. depth sputtered and fraction of metal coating sputtered vs. depth sputtered, the development of the crater profile can be followed and the cause of the depth resolution problem evaluated.