RF-plasma treatments of surface-conductive alkali-lead silicate glass and microchannel plate devices

RF-plasma treatments of surface-conductive alkali-lead silicate glasses and microchannel plate devices were performed using argon, ammonia and nitrogen gas mixtures. The effects of the different plasma-treatments on the composition of the glass surface were studied using Secondary Ion Mass Spectroscopy (SIMS) and X-ray Photoelectron Spectroscopy (XPS). A surface depletion of rubidium and cesium due to migration into the bulk of the glass and due to sputtering/vaporization of alkali ions from the glass surface was observed after the plasma treatments. The use of N₂ and NH₃ in the plasma gas resulted in the incorporation of nitrogen into the glass surface up to a depth of approximately 100 angstroms. The effect of the plasma treatments on the water adsorptivity of actual microchannel plates was studied using Temperature Programmed Desorption (TPD). The TPD results showed that the argon plasma treatments helped in improving the short-term water adsorptivity properties of the microchannel plate devices, but long-term (>6 months in air) benefits were lost.