Single Impacts of C60 on Solids: Emission of Electrons, Ions and Prospects for Surface Mapping
Single Impacts of C60 on Solids: Emission of Electrons, Ions and Prospects for Surface Mapping
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DOI：
10.1021/jp9073703
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发表时间：
2010-04-01
影响因子：
3.7
通讯作者：
Schweikert, E. A.
中科院分区：
文献类型：
--
作者：
Verkhoturov, S. V.;Eller, M. J.;Schweikert, E. A.
我们报告了15 keV C-60（+）和30 keV C-60（2+）对Al，Si，Au，CsI，甘氨酸和鸟嘌呤靶的撞击产生的二次离子和电子的共发射。该研究是通过电子发射显微镜和飞行时间（ToF）质谱仪的组合进行的。电子发射发生在动力学发射阈值附近，但对于所有研究的靶，产率是显著的（>3）。研究的射弹-靶组合的一个关键观察是，对于平坦和均匀的样品，电子发射与共发射的二次离子的数量和类型之间没有相关性。这一观察证实了“位置质谱”的新概念。在这种方法中，以逐个事件轰击检测模式探测表面。单个C-60射弹的撞击是通过电子发射来定位的。结合相应的二次离子信息的位置允许映射卷曲分子的分布。位置质谱的独特功能是能够识别来自单个射弹撞击的共发射离子。为了测试这一概念，电子发射显微镜与I ToF质谱仪相结合;该设备同步检测电子和离子。该方法的空间分辨率取决于二次电子的动能和角分布以及电子光学的像差。位置质谱的初步测试显示空间分辨率为1.2 μ m。随着所用电子光学技术的改进和产生更多电子发射的射弹的应用，预计将取得进展。
We report on the co-emission of secondary ions and electrons resulting from 15 keV C-60(+) and 30 keV C-60(2+) impacts on targets of Al, Si, Au, CsI, glycine, and guanine. The Study has been performed by the combination of an electron emission microscope and a time-of-flight (ToF) mass spectrometer. The electron emission occurs near the kinetic emission threshold, yet yields are notable (>3) for all investigated targets. A key observation for the projectile-target combinations studied is the absence of correlation between the electron emission and the number and type of co-emitted secondary ions for flat and homogeneous samples. This observation validates a novel concept of "positional mass spectrometry". In this approach a surface is probed in the event-by-event bombardment detection mode. Impacts of an individual C-60 projectile are localized via electron emission. The location combined with the corresponding secondary ion information allows to map the distribution of curl-ace molecules. The unique feature of positional mass spectrometry is the ability to identify co-emitted ions from a single projectile impact. To test the concept an electron emission microscope has been combined with I ToF mass spectrometer; the device operates with synchronized detection of electrons and ions. The spatial resolution of the method depends on the kinetic energy and angular distribution of the secondary electrons and the aberrations of the electron optics. Initial tests of positional mass spectrometry showed a spatial resolution of 1.2 mu m. Progress is anticipated with improvements in the electron optics used and application of projectiles generating more prolific electron emission.