Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland.
Physics Institute, Space Research and Planetary Sciences, University of Bern , Sidlerstrasse 5, CH-3012 Bern, Switzerland.
Anal Chem. 2018 Feb 20;90(4):2692-2700. doi: 10.1021/acs.analchem.7b04539. Epub 2018 Feb 5.
State-of-the-art laser ablation (LA) depth-profiling techniques (e.g. LA-ICP-MS, LIBS, and LIMS) allow for chemical composition analysis of solid materials with high spatial resolution at micro- and nanometer levels. Accurate determination of LA-volume is essential to correlate the recorded chemical information to the specific location inside the sample. In this contribution, we demonstrate two novel approaches towards a better quantitative analysis of LA craters with dimensions at micrometer level formed by femtosecond-LA processes on single-crystalline Si(100) and polycrystalline Cu model substrates. For our parametric crater evolution studies, both the number of applied laser shots and the pulse energy were systematically varied, thus yielding 2D matrices of LA craters which vary in depth, diameter, and crater volume. To access the 3D structure of LA craters formed on Si(100), we applied a combination of standard lithographic and deep reactive-ion etching (DRIE) techniques followed by a HR-SEM inspection of the previously formed crater cross sections. As DRIE is not applicable for other material classes such as metals, an alternative and more versatile preparation technique was developed and applied to the LA craters formed on the Cu substrate. After the initial LA treatment, the Cu surface was subjected to a polydimethylsiloxane (PDMS) casting process yielding a mold being a full 3D replica of the LA craters, which was then analyzed by HR-SEM. Both approaches revealed cone-like shaped craters with depths ranging between 1 and 70 μm and showed a larger ablation depth of Cu that exceed the one of Si by a factor of about 3.
最先进的激光烧蚀（LA）深度剖析技术（例如：LA-ICP-MS、LIBS 和 LIMS）可实现微纳米级别的固体材料的高空间分辨率化学成分分析。准确确定 LA 体积对于将记录的化学信息与样品内部的特定位置相关联至关重要。在本研究中，我们展示了两种新颖的方法，用于更好地对飞秒激光烧蚀过程在单晶 Si（100）和多晶 Cu 模型衬底上形成的微米级尺寸的 LA 撞击坑进行定量分析。对于我们的参数化撞击坑演化研究，系统地改变了施加的激光脉冲数和脉冲能量，从而产生了在深度、直径和撞击坑体积上均有所不同的 2D LA 撞击坑矩阵。为了获取在 Si（100）上形成的 LA 撞击坑的 3D 结构，我们采用了标准光刻和深反应离子刻蚀（DRIE）技术的组合，随后对之前形成的撞击坑横截面进行了高分辨率扫描电子显微镜（HR-SEM）检查。由于 DRIE 不适用于金属等其他材料类别，因此开发并应用了一种替代的、更通用的制备技术，用于在 Cu 衬底上形成的 LA 撞击坑。在初始 LA 处理之后，Cu 表面经过聚二甲基硅氧烷（PDMS）铸模处理，得到一个完全复制 LA 撞击坑的 3D 模具，然后通过 HR-SEM 进行分析。这两种方法均揭示出具有 1 至 70 μm 深度的锥形撞击坑，并且显示出 Cu 的较大消融深度，比 Si 高出约 3 倍。
