Comparison of sulfide films formed on copper by surface segregation and wet H2S exposure

It is shown that the sulfide films formed in a technical vacuum on copper are composed mainly of Cu/sub 2/O and Cu/sub 2/S, and have a composition slightly different from films formed by an H/sub 2/S exposure. AES (Auger electron spectroscopy) depth profiles and ESCA (electron spectroscopy for chemical analysis) experiments showed that surface segregated sulfide films formed in ultrahigh vacuum as well as those formed in a technical vacuum disappeared on air exposure of approximately 5 to 7 days. At the same time the characteristic oxygen photoemission lines from Cu/sub 2/O and CuO increased significantly. It is concluded that the sulfur was entirely replaced by oxygen and that the resulting free sulfur, which has a high vapor pressure at room temperature, simply evaporated. A similar tendency was observed for the sulfide film formed on wet H/sub 2/S exposure (1.5-2 p.p.m.) after a 7 day air exposure. An AES depth profile showed that part of the sulfide film was buried by oxide and part of it vanished. The polarity effect on thick films formed by wet H/sub 2/S was significant; it decreased with decreasing film thickness. A polarity effect was also found on a sulfur segregated surface formed in technical vacuum; however, it degraded rapidly with time.<>