Low‐energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well‐defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF₂ as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF₂ is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF₂ can be used as reference, its atomic surface concentrations have to be determined. Here, 3‐keV He⁺ scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. High‐purity CaF₂ is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF₂ (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu.

中文翻译：

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高灵敏度低能离子散射对钙和氟的定量分析：氟化钙

低能离子散射（LEIS）探测外表面的原子组成。定义明确的参考样品用于定量。对于像氟和钙这样的元素，要找到合适，清洁和均质的参考并不容易，因为氟是一种气体，而钙是一种非常活泼的金属。与表面分析技术（例如XPS）相比，LEIS的极高表面敏感性使其难以使用诸如CaF _2的稳定化合物作为参考，因为这些化合物在原子尺度上并不均质。对于LEIS，预计CaF ₂的原子比F / Ca = 2.0。因此，在CaF ₂可以用作参考之前，必须确定其原子表面浓度。在这里，3keV He ⁺LiF（001）单晶的散射，Ca的蒸发层和Cu箔用作基本参考。高纯度CaF ₂有两种形式：单晶和粉末。作为实际参考，粉末是优选的，因为如果大量杂质偏析到表面上，它们将分散在较大的表面积上。发现CaF ₂（111）和粉末都具有相似的F / Ca原子比。这确认了两个样品的F终止。对于粉末，与单晶相比，F和Ca信号降低了0.77±0.03。已经确定了F，Ca和Cu的原子敏感性因子和相对敏感性因子。