MeV能量Si^+引起二次离子发射的研究

Study of Secondary Ion Emissions Induced by MeV Si^+

利用北京大学2×1.7 MV串列加速器终端的飞行时间(TOF)谱仪,分别用1.5、2.0和3.0MeV三种能量的初级束Si+轰击样品来研究其二次离子发射现象,使用的样品包括石墨、碳纳米管等。结果表明,采用合理的降噪方法后得到了高信噪比和高时间分辨率的二次离子质谱,实现了全质量范围无遗漏记谱。利用H-C12峰刻度之后,计算得出二次离子各成分的最可能构成及产额,碳纳米管样品表面氢质量含量为8.15%。同时,发现MeV能区二次离子产额与Si+阻止本领之间的关系并非简单的正相关。

Si＋ beams of l. 5MeV, 2.0MeV and 3.0MeV were used to investigate the secondary ion emission of the samples, such as graphite, carbon nanotubes （CNT） etc, using the accelerator - based time of flight （TOF） SIMS in the Laboratory of 2 × 1.7 MV tandem accelerator in Peking University. Compared with the previous data, the spectrum was much clearer attribute to the improvement of the noise reduction and the increase of the flight distance. The spectrums were calibrated using the H and Cl2 peaks, which showed the mass of hydrogen on the surface of CNT reaches 8.15%. The components and products of the secondary ions were precisely calculated and the products were found to be not positively related with the stopping powder of Si＋ in the samples.