Vaporlike phase of amorphous SiO2 is not a prerequisite for the core/shell ion tracks or ion shaping

摘要: When a swift heavy ion (SHI) penetrates amorphous $\mathrm{Si}{\mathrm{O}}_{2}$, core/shell (C/S) track is formed, which consists of lower-density core and higher-density shell. According to the conventional inelastic thermal spike (iTS) model represented by pair coupled heat equations, C/S tracks are believed form via ``vaporization'' melting $\mathrm{Si}{\mathrm{O}}_{2}$ induced SHI (V-M model). However, does not describe what vaporization in confined ion-track geometry with condensed matter density is. Here we reexamine this hypothesis. While total radii determined small angle x-ray scattering good agreement calculated from iTS under high electronic stopping power $({S}_{e})$ irradiations (g10 keV/nm), deviations between them evident at low-${S}_{e}$ irradiation (3--5 keV/nm). Even though calculations exclude low ${S}_{e}$, both formation shaping nanoparticles (NPs) experimentally confirmed, indicating inconsistency V-M model. Molecular dynamics (MD) simulations based on two-temperature model, an atomic-level modeling extension iTS, clarified that ``vaporlike'' phase exists ${S}_{e}\ensuremath{\sim}5$ keV/nm or higher as nonequilibrium where atoms have kinetic energies than energy, but nearly density. Simultaneously, indicate 50-MeV Si $({S}_{e}\ensuremath{\sim}3$ nevertheless induced. final variations very values (both experiments), MD show can be explained flow liquid metal NP into transient low-density during first \ensuremath{\sim}10 ps after impact. The correlates recovery process silica matrix emitting pressure wave. Thus, prerequisite for shaping.