Temperature of thermal spikes in amorphous silicon nitride films produced by 1.11 MeV C impacts

Kitayama, Takumi*; Nakajima, Kaoru*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto  ; Sataka, Masao*; Tsujimoto, Masahiko*; Isoda, Shoji*; Kimura, Kenji*

According to an inelastic-thermal-spike (i-TS) model, which is regarded as the most promising among several models proposed to explain the formation of an ion track, a part of the energy deposited to electrons in a solid by a swift heavy ion is gradually transferred to target atoms via electron-phonon coupling. The temperature of target atoms rises along the ion path and consequently an ion track is formed when the temperature exceeds the melting point. Therefore, the temperature of target atoms along the ion path is regarded as a key parameter for the i-TS model; however, such a spatiotemporally-localized temperature is difficult to measure because the processes involved occur in a very short period ( 10 s) and in a very localized area. In this study, the temperature of target atoms along the ion path is estimated experimentally with transmission-electron-microscope (TEM) observation of desorption of Au nanoclusters (the melting point 1300 K) on an amorphous SiN thin film under 1.1-MeV C-ion irradiation to the fluence of 510 ions/cm. TEM images show that Au nanoclusters, deposited at the areal density of 1.1610 particles/cm, disappear in a surface area with a diameter of 20 nm around each ion track, whose diameter is 4 nm, after irradiation. This indicates that the temperature at the film surface rises locally to at least 1300 K by the ion bombardment.