National Physical Laboratory, Teddington, Middlesex, United Kingdom.
Anal Chem. 2012 Sep 18;84(18):7865-73. doi: 10.1021/ac301567t. Epub 2012 Sep 5.
The depth profiling of organic materials with argon cluster ion sputtering has recently become widely available with several manufacturers of surface analytical instrumentation producing sources suitable for surface analysis. In this work, we assess the performance of argon cluster sources in an interlaboratory study under the auspices of VAMAS (Versailles Project on Advanced Materials and Standards). The results are compared to a previous study that focused on C(60)(q+) cluster sources using similar reference materials. Four laboratories participated using time-of-flight secondary-ion mass spectrometry for analysis, three of them using argon cluster sputtering sources and one using a C(60)(+) cluster source. The samples used for the study were organic multilayer reference materials consisting of a ∼400-nm-thick Irganox 1010 matrix with ∼1 nm marker layers of Irganox 3114 at depths of ∼50, 100, 200, and 300 nm. In accordance with a previous report, argon cluster sputtering is shown to provide effectively constant sputtering yields through these reference materials. The work additionally demonstrates that molecular secondary ions may be used to monitor the depth profile and depth resolutions approaching a full width at half maximum (fwhm) of 5 nm can be achieved. The participants employed energies of 2.5 and 5 keV for the argon clusters, and both the sputtering yields and depth resolutions are similar to those extrapolated from C(60)(+) cluster sputtering data. In contrast to C(60)(+) cluster sputtering, however, a negligible variation in sputtering yield with depth was observed and the repeatability of the sputtering yields obtained by two participants was better than 1%. We observe that, with argon cluster sputtering, the position of the marker layers may change by up to 3 nm, depending on which secondary ion is used to monitor the material in these layers, which is an effect not previously visible with C(60)(+) cluster sputtering. We also note that electron irradiation, used for charge compensation, can induce molecular damage to areas of the reference samples well beyond the analyzed region that significantly affects molecular secondary-ion intensities in the initial stages of a depth profile in these materials.
利用氩原子簇溅射对有机材料进行深度剖析，最近已得到广泛应用，几家表面分析仪器制造商都生产出了适用于表面分析的原子簇源。在这项工作中，我们在 VAMAS（先进材料和标准凡尔赛项目）的主持下，对氩原子簇源进行了实验室间研究，评估其性能。研究结果与之前使用类似参考材料聚焦 C(60)(q+)原子簇源的研究进行了比较。有四个实验室参与了这项研究，使用飞行时间二次离子质谱法进行分析，其中三个实验室使用氩原子簇溅射源，一个实验室使用 C(60)(+)原子簇源。研究中使用的样品是有机多层参考材料，由厚度约为 400nm 的 Irganox 1010 基体和深度约为 50、100、200 和 300nm 的厚度约为 1nm 的 Irganox 3114 标记层组成。与之前的报告一致，氩原子簇溅射被证明可以有效地通过这些参考材料保持恒定的溅射产率。此外，这项工作还表明，可以使用分子二次离子来监测深度分布，并且可以达到接近半峰全宽(fwhm)为 5nm 的深度分辨率。参与者分别将氩原子簇的能量设置为 2.5keV 和 5keV，氩原子簇的溅射产率和深度分辨率与从 C(60)(+)原子簇溅射数据推断出的结果相似。然而，与 C(60)(+)原子簇溅射不同的是，观察到溅射产率随深度的变化可以忽略不计，并且两个参与者获得的溅射产率的重复性优于 1%。我们发现，使用氩原子簇溅射时，标记层的位置可能会发生高达 3nm 的变化，这取决于用于监测这些层中材料的二次离子，这是以前使用 C(60)(+)原子簇溅射无法看到的效果。我们还注意到，用于电荷补偿的电子辐照会在参考样品的远超出分析区域的地方诱导分子损伤，这会显著影响这些材料深度剖面上的初始阶段的分子二次离子强度。
