Factors influencing surface carbon contamination in ambient-pressure x-ray photoelectron spectroscopy experiments
Factors influencing surface carbon contamination in ambient-pressure x-ray photoelectron spectroscopy experiments
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DOI：
10.1116/6.0001013
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发表时间：
2021-07-01
影响因子：
2.9
通讯作者：
Novotny, Zbynek
中科院分区：
文献类型：
--
作者：
Comini, Nicolo';Huthwelker, Thomas;Novotny, Zbynek
碳污染是一个臭名昭著的问题，对表面科学实验有着巨大的影响，特别是在近大气条件下。虽然它经常在出版物中提到影响实验结果时，但很少详细分析。我们使用暴露于水蒸气和液态水的大规模（50 x 10 mm（2））金红石TiO 2（110）单晶进行了环境压力X射线光电子能谱实验，以检查在清洁和充分制备的表面上外来碳物种（无机和烃）的积聚。我们的研究结果突出了各种因素和环境条件，如光束照明，残余气体压力和成分，以及与液态水的相互作用，如何在表面上碳的积累中发挥作用。很明显，束诱导效应局部增加了辐照区域的碳量。与光照射无关的起始条件决定了初始的总体污染水平。令人惊讶的是，光束诱导的碳积聚的速率对于不同的起始实验条件没有显著变化。以10毫巴的量级引入分子氧允许在X射线照射期间进行快速表面清洁。当氧分压与毫巴压力范围内的水蒸气分压相当时，可以完全去除表面碳污染，如通过将TiO 2（110）表面同时暴露于15毫巴的水蒸气和15毫巴的分子O-2所测试的。此外，我们的数据支持这样的假设，即通过水分子的竞争性吸附从腔室壁中逐渐去除碳物种发生在反复暴露于水蒸气之后。我们相信，我们的研究结果将是有用的，未来的研究液-固界面使用招标x射线，碳污染起着重要的作用。(C)2021年作者。
Carbon contamination is a notorious issue that has an enormous influence on surface science experiments, especially in near-atmospheric conditions. While it is often mentioned in publications when affecting an experiment's results, it is more rarely analyzed in detail. We performed ambient-pressure x-ray photoelectron spectroscopy experiments toward examining the build-up of adventitious carbon species (both inorganic and hydrocarbons) on a clean and well-prepared surface using large-scale (50 x 10 mm(2)) rutile TiO2(110) single crystals exposed to water vapor and liquid water. Our results highlight how various factors and environmental conditions, such as beam illumination, residual gas pressure and composition, and interaction with liquid water, could play roles in the build-up of carbon on the surface. It became evident that beam-induced effects locally increase the amount of carbon in the irradiated area. Starting conditions that are independent of light irradiation determine the initial overall contamination level. Surprisingly, the rate of beam-induced carbon build-up does not vary significantly for different starting experimental conditions. The introduction of molecular oxygen in the order of 10 mbar allows for fast surface cleaning during x-ray illumination. The surface carbon contamination can be completely removed when the oxygen partial pressure is comparable to the partial pressure of water vapor in the millibar pressure range, as was tested by exposing the TiO2(110) surface to 15 mbar of water vapor and 15 mbar of molecular O-2 simultaneously. Furthermore, our data support the hypothesis that the progressive removal of carbon species from the chamber walls by competitive adsorption of water molecules takes place following repeated exposure to water vapor. We believe that our findings will be useful for future studies of liquid-solid interfaces using tender x rays, where carbon contamination plays a significant role. (C) 2021 Author(s).