Brajković Marko, Bogdanović Radović Ivančica, Barac Marko, Cosic Donny Domagoj, Siketić Zdravko
Ruđer Bošković Institute, Bijenička c. 54, HR-10000 Zagreb, Croatia.
J Am Soc Mass Spectrom. 2021 Oct 6;32(10):2567-2572. doi: 10.1021/jasms.1c00200. Epub 2021 Sep 14.
Time-of-flight Secondary Ion Mass Spectrometry (TOF SIMS) with MeV primary ions offers a fine balance between secondary ion yield for molecules in the mass range from 100 to 1000 Da and beam spot size, both of which are critical for imaging applications of organic samples. Using conically shaped glass capillaries with an exit diameter of a few micrometers, a high energy heavy primary beam can be collimated to less than 10 μm. In this work, imaging capabilities of such a setup are presented for some organic samples (leucine-evaporated mesh, fly wing section, ink deposited on paper). Lateral resolution measurement and molecular distributions of selected mass peaks are shown. The negative influence of the beam halo, an unavoidable characteristic of primary beam collimation with a conical capillary, is also discussed. A new start trigger for TOF measurements based on the detection of secondary electrons released by the primary ion is presented. This method is applicable for a continuous primary ion beam, and for thick targets that are not transparent to the primary ion beam. The solution preserves the good mass resolution of the thin target setup, where the detection of primary ions with a PIN diode is used for a start trigger, reduces the background, and enables a wide range of samples to be analyzed.
采用兆电子伏特初级离子的飞行时间二次离子质谱（TOF SIMS）在质量范围为100至1000道尔顿的分子的二次离子产率与束斑尺寸之间实现了良好的平衡，这两者对于有机样品的成像应用都至关重要。使用出口直径为几微米的锥形玻璃毛细管，可以将高能重初级束准直到小于10微米。在这项工作中，展示了这种设置对一些有机样品（亮氨酸蒸发网、蝇翼切片、纸上沉积的墨水）的成像能力。展示了横向分辨率测量和选定质量峰的分子分布。还讨论了束晕的负面影响，束晕是锥形毛细管对初级束进行准直时不可避免的一个特征。提出了一种基于检测初级离子释放的二次电子的TOF测量新启动触发器。该方法适用于连续初级离子束以及对初级离子束不透明的厚靶。该解决方案保留了薄靶设置的良好质量分辨率，在薄靶设置中使用PIN二极管检测初级离子作为启动触发器，减少了背景，并能够分析各种样品。
