Formation and Destruction of Gas-Filled Bubbles in the Surface Layer of Glass under the Action of Electron-Proton Plasma

Abstract—

The influence of electron-proton irradiation on the process of changing the surface structure of K‑208 glass, caused by the formation of gas-filled bubbles and their destruction, is studied by atomic-force microscopy (AFM). These phenomena are associated with the formation of hydrogen atoms H in the process of the recombination of protons with electrons injected into the glass and those that appeared in it during ionization. The migration of hydrogen atoms and their aggregation into H-clusters in the vicinity of glass structure defects leads to the formation of molecular hydrogen (H₂) bubbles. The glass is exposed to electrons and protons with energies of 40 and 20 keV, respectively. Irradiation is carried out in a vacuum chamber with a residual pressure of 10^–4 Pa. At a fixed value of the proton flux density φ_р = 5.5 × 10¹⁰ cm^–2 s^–1, the electron flux density φ_e varies in the range (0–16.8) × 10¹⁰ cm^–2 s^–1. It is shown that the size of the bubbles depends on the ratio of the parameters φ_e and φ_р. Analysis of the experimental data suggests that the destruction of a bubble occurs with a local decrease in the thickness of its cap to 10–20 nm, as a result of heating and growth in the direction normal to the surface under the pressure of the accumulating gas. It is also found that electrostatic discharges developing along the irradiated glass surface stimulate the destruction of bubbles.