A study of collective electronic excitation by ion energy loss spectroscopy

本文将用于固体表面分析的高分辨离子散射光谱技术改进为透射能量损失光谱技术。利用该光谱仪，以20-60 eV的分辨率，测量了能量为-100 KeV的H^+和He^+离子透过厚度为7-20 nm的碳膜的能量损失分布。目前的结果总结如下。(1)No观察到由于单个等离子体激元激发（即集体电子激发）而产生的峰值。在~ 7 nm碳膜中观察到一个新的能量损失峰，其能量损失峰在200 eV附近，其原因尚在研究中。（2）由零能量损失峰强度，得到100 KeV H^+和He^+的电子平均自由程分别为1.2和1.4 nm。这些值与电子在相同速度下的电子平均自由程相当。（3）能量损失峰的增加归因于离子轰击对碳键的修饰。同时发现这种效应是由于电子激发的结果。（4）100 KeV H ^+的能量损失峰与50 KeV H^+的能量损失峰几乎相等，表明能量损失没有分子效应。17 nm薄膜在100 KeV H_2^+中的存活概率为6 × 10 ~（-1）<-3>。

High resolution ion scattering spectroscopy which was developed for solid surface analysis has been modified for transmission energy loss spectrosbopy. Using this spectroscopy with a resolution of 20-60 eV, the energy loss distribution of H^+ and He^+ with the energy of -100 KeV transmitted through carbon films with thickness of 7-20 nm were measured. The present results are summarized as follows.(1)No peak due to single plasmon excitation, viz, collective electronic excitation was observed. A new energy loss peak around 200 eV for -7 nm carbon films was observed and the origin is under investigation.(2)From the zero energy loss peak intensity, the electronic mean free path was obtained as 1.2 and 1.4 nm for 100 KeV H^+ and He^+, respectively. These values are comparable with the electronic mean free path of electrons at the same velocities.(3)The increase of the energy loss peak was observed and this effect is ascribed to the modification of carbon bond due to ion bombardment. It id also found that this effect is due to the electronic excitation.(4)The energy loss peak of 100 KeV H_2^+ was found to nearly equal to that of 50 KeV H^+ , indicating no molecular effect on the energy loss. The survival probability of 100 KeV H_2^+ for 17 nm film was 6X10^<-3>.