Kousuke Moritani

Destructions of a DNA array and graphene on silicon oxide due to collisions with Ar gas clusters are investigated in order to develop a new method for detecting the impact of these clusters on a solid surface. Since both materials are conductive, sputtering is detected from their continuity. In the case of graphene, surface coverage is measured from the reflectivity of visible light. Furthermore, changes in the honeycomb structure can be identified from the acquired Raman spectrum.

We have investigated the secondary ion emission from 1,4-didodecylbenzene (DDB) thin film under Ar cluster and water cluster bombardment. We have found that the DDB molecule was protonated by the water cluster collision below 10 eV/molecule and formed the protonated molecular ion [M+H]+, while the molecular radical ion M+ was detected above 12 eV/molecule, although aromatic molecules typically formed only M+ under the ion bombardment.<br>In this paper we disuss the mechanism of molecular ion formation from the 1,4-DDB thin films under the cluster ion bombardment.

We have investigated the secondary ion emission from organic molecular thin film under molecular cluster ion bombardment. The water cluster ion enhanced the protonated molecular ion [M+H]⁺ yield of polar molecules. We have found that the water cluster ion beam also enhanced the [M+H]⁺ yields of aromatic molecule which typically formed only molecular radical ion M⁺ under the ion bombardment. In this paper we disuss the reaction mechanism of molecular ion formation induced by the molecular cluster collision.

有機材料の構造解析手法の一つとして、Arガスクラスターイオンビーム（GCIB）を一次イオン源とする飛行時間型二次イオン質量分析装置（TOF-SIMS）等が普及している。Ar-GCIBはクラスターサイズ分布が広いため、特定のクラスターサイズを選別可能なマスフィルターが求められている。そこで本研究では、二段の回転電場により、特定の質量電荷比のイオンのみを光軸上へ回帰可能なマスフィルターの開発を行った。

サイズを選別した水およびメタノールクラスターイオンビームをアスパラギン酸薄膜に照射し、表面から放出された二次イオンを質量分析した。水およびメタノールの巨大クラスター照射による有機分子のイオン化には、試料中の残留水素からのプロトン付加反応の他に、クラスターと試料分子間でのプロトン交換反応が寄与していることがわかった。また、この反応は低エネルギー領域（～3.3eV）で促進されていることがわかった。

We experimentally demonstrate the conditions where rare-gas cluster ion dissociates depending on the elastic response at the collision. Cluster ion consisting of thousands of argon atoms collide with the five kinds of metals at an incident energy per atom of less than 10 eV. The prominent ions in the mass spectra detected are dissociated ions such as dimer (Ar_2^+) or trimer ions (Ar_3^+). The branching ratio of the ion yield Ar_2^+/ΣAr_n^+(n &ge; 2), representing the dissociation rate, is significantly different by the metals. As a result, we found the dissociation rate of cluster ion is linearly increased with the impulsive stress acting on the contact area between the cluster ion and the metal surface. In addition, we discussed the possibility the result is applied to a new evaluation method of material strength.