Importance of Carbon Contamination in High-Resolution (FEG) EPMA of Silicate Minerals
Importance of Carbon Contamination in High-Resolution (FEG) EPMA of Silicate Minerals
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DOI：
10.1017/s1431927615000288
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发表时间：
2015-04
影响因子：
2.8
通讯作者：
B. Buse;S. Kearns
中科院分区：
文献类型：
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作者：
B. Buse;S. Kearns
本文研究了在5 kV，0.7- 4keV X射线能量下，碳污染对碳包硅酸盐矿物分析的影响。对于单个点分析，发现碳在束点附近沉积存款，形成环形沉积物，对分析没有影响。碳污染对于密集分析变得重要，例如多点样带，其中每次后续分析都与先前分析的碳环重叠。由于污染的X射线强度损失是最严重的低过电压元素，如钙，钾与碳沉积一致，有效地减少光束能量。污染率的计算和使用液氮冷阱显示，大大减少了碳沉积量。一个互补的经验校正开发，以纠正从测量的碳的X射线强度损失，假设碳是一个薄膜，并与来自薄膜计算的校正进行比较。PENEPMA PE电子探针显微分析（PENEPMA）的计算证实，不对称的碳沉积可以忽略不计的X射线能量的强度损失主要是通过能量损失的电子束。使用冷阱和/或经验校正高空间分辨率分析（ca. 400 nm之间的点）是可实现的分析误差约为。1- 3%。
Abstract The effect of carbon contamination on the analysis of carbon-coated silicate minerals at 5 kV for X-ray energies 0.7–4 keV is examined. For individual spot analyses, carbon is found to deposit adjacent to the beam spot forming ring-shaped deposits with no impact on the analysis. Carbon contamination becomes important for closely spaced analyses such as multipoint transects, where each subsequent analysis overlaps the carbon ring of the previous analysis. X-ray intensity loss due to contamination is most severe for low-overvoltage elements such as Ca K consistent with carbon deposition effectively reducing beam energy. Rates of contamination are calculated and the use of a liquid nitrogen cold trap is shown to greatly reduce the amount of carbon deposited. A complimentary empirical correction is developed to correct for X-ray intensity loss from measured carbon, assuming the carbon is a film, and is compared with corrections derived from thin film calculations. PENELOPE electron probe microanalysis (PENEPMA) calculations confirm that asymmetry of the carbon deposition can be ignored for X-ray energies where intensity loss is predominantly through energy loss of beam electrons. Using a cold trap and/or an empirical correction high spatial resolution analysis (ca. 400 nm between points) is achievable with analytical errors of ca. 1–3%.