[16p-315-1~11] GFIS（電界電離ガスイオン源）ガスイオン顕微鏡技術とその材料・デバイス研究開発への応用：現状と今後の展望

▲ [16p-315-11] Interaction of gas field ionized nitrogen with silicon

〇(P)Schmidt Marek Edward¹、Zhang Xiaobin¹、Oshima Yoshifumi¹、The Anh Le¹、Yasaka Anto²、Kanzaki Teruhisa¹、Muruganathan Manoharan¹、Akabori Masashi¹、Shimoda Tatsuya¹、Mizuta Hiroshi¹ (1.JAIST、2.Hitachi High-Tech Science Corp.)

キーワード：Nitrogen, Molecular Dynamics

A larger number of gas molecules (among them hydrogen, helium, nitrogen and neon) can be ionized by the gas field ion source (GFIS) and used as projectiles in focused ion beam (FIB) systems. Among them, the nitrogen stands out as it forms a very strong covalent bond. It is not yet fully understood how this N₂ molecule behaves during gas field ionization and sample interaction, i.e. if the bond is broken during ionization. The mass spectrum of electron ionized N₂ gas shows a small amount of N⁺ and a larger amount of N₂⁺. Here, we report scanning transmission electron microscopy (STEM) analysis of cross sections extracted from silicon bombarded with gas field ionized N₂ molecules with a line dose from 0.24 and 9.5x10³ ion/nm. The extracted implantation depths for ion energies of 25 and 16 keV are compared with theoretical values and suggest that the bond sustains the field ionization and is broken during sample interaction. We use first principle molecular dynamics simulation to support this finding (Figure 1b), in particular that the covalent bond is broken within the first few atomic layers of the impinged silicon target.