Anomalous Time-of-Flight Distributions Observed for Argon Implanted in Silicon and Resputtered by ${\mathrm{Ar}}^{+}$-Ion Bombardment

A Si substrate is bombarded by 3-keV ${\mathrm{Ar}}^{+}$ ions. From time-of-flight spectra of resputtered Ar neutrals at various target temperatures, we conclude that Ar-bubble formation takes place in the amorphized-Si top layer. The bubbles form and open during etching. The average kinetic energy of the Ar atoms is in agreement with the calculated average potential energy of the Ar atoms inside the bubbles.