Exploring Biases in Atom Probe Tomography Compositional Analysis of Minerals
Exploring Biases in Atom Probe Tomography Compositional Analysis of Minerals
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DOI：
10.1111/ggr.12395
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发表时间：
2021-07-08
影响因子：
3.8
通讯作者：
Perez-Huerta, Alberto
中科院分区：
文献类型：
--
作者：
Cappelli, Chiara;Smart, Sandi;Perez-Huerta, Alberto
原子探针层析成像（APT）是一种重要的纳米地球化学技术，在地球科学中有着广泛的应用。估计化学计量的矿物成分是特别具有挑战性的纳米尺度的功能。APT为金属系统提供了可靠的测量，但氧化物的可靠性是有问题的，特别是由于缺氧。在这里，我们使用激光辅助APT来比较尖晶石和石榴石晶体的结果。APT组成的结果进行了比较，通过电子探针，以确定可能的APT分析不准确。通过大量的数据处理，包括相关直方图、二维离子分布图和一维元素浓度分布图，揭示了导致矿物化学计量偏差的可能机制。多重事件和中性分子的形成可能是导致原子亏损的主要过程。特别地，与铝和氧缺陷相关的相同同位素-相同电荷状态离子对的量表明，死空间-死时间窗口中的共蒸发可能导致检测到的离子的显著减少。此外，分子物种的解离和直流蒸发可以部分地解释进一步的原子损失。总体而言，更好的APT组成估计得到尖晶石，它具有较小的变化，在晶格位置和更大的整体晶格对称性，更高的热导率和较低的带隙相比，石榴石。
Atom probe tomography (APT) is emerging as a key nanogeochemistry technique for diverse geoscience applications. Estimating stoichiometric mineral compositions is particularly challenging for features at nanoscale. APT provides reliable measurements for metallic systems but the reliability for oxides is problematic, notably due to oxygen deficit. Here, we use laser-assisted APT to compare results for spinel and garnet crystals. APT compositional results were compared with those by electron microprobe to determine the possible APT analytical inaccuracy. Extensive data processing was accomplished, including correlation histograms, 2D ion distribution maps and 1D elements concentration profiles, to disclose the possible mechanisms leading to mineral stoichiometry biases. Multiple events and neutral molecules formation are probable the main processes responsible for atom deficit. In particular, the amount of the same isotope-same charge state ion pairs correlated with aluminium and oxygen deficits suggests that the co-evaporation in a dead space-dead time window could lead to a significant decrease of detected ions. Also, molecular species dissociation and direct current evaporation could partially account for further atom loss. Overall, better APT compositional estimation was obtained for spinel, which has lesser variation in lattice sites and greater overall lattice symmetry, higher thermal conductivity and lower band gap compared with garnet.