Boeckers Hannah, Swiderek Petra, Rohdenburg Markus
Institute for Applied and Physical Chemistry, University of Bremen, Leobener Str. 5, 28359 Bremen, Germany.
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, Leipzig University, Linnéstr. 2, 04103 Leipzig, Germany.
Nanomaterials (Basel). 2022 Dec 15;12(24):4455. doi: 10.3390/nano12244455.
Focused Electron Beam Induced Deposition (FEBID) is a unique tool to produce nanoscale materials. The resulting deposits can be used, for instance, as humidity or strain sensors. The humidity sensing concept relies on the fact that FEBID using organometallic precursors often yields deposits which consist of metal nanoparticles embedded in a carbonaceous matrix. The electrical conductivity of such materials is altered in the presence of polar molecules such as water. Herein, we provide evidence that the interaction with water can be enhanced by incorporating nitrogen in the deposit through post-deposition electron irradiation in presence of ammonia (NH). This opens the perspective to improve and tune the properties of humidity sensors fabricated by FEBID. As a proof-of-concept experiment, we have prepared carbonaceous deposits by electron irradiation of adsorbed layers of three different precursors, namely, the aliphatic hydrocarbon -pentane, a simple alkene (2-methyl-2-butene), and the potential Ru FEBID precursor bis(ethylcyclopentadienyl)ruthenium(II). In a subsequent processing step, we incorporated C-N bonds in the deposit by electron irradiation of adsorbed NH. To test the resulting material with respect to its potential humidity sensing capabilities, we condensed sub-monolayer quantities of water (HO) on the deposit and evaluated their thermal desorption behavior. The results confirm that the desorption temperature of HO decisively depends on the degree of N incorporation into the carbonaceous residue which, in turn, depends on the chemical nature of the precursor used for deposition of the carbonaceous layer. We thus anticipate that the sensitivity of a FEBID-based humidity sensor can be tuned by a precisely timed post-deposition electron and NH processing step.
聚焦电子束诱导沉积（FEBID）是一种用于制备纳米级材料的独特工具。所得沉积物可用于例如湿度或应变传感器。湿度传感概念基于这样一个事实，即使用有机金属前驱体的FEBID通常会产生由嵌入碳质基质中的金属纳米颗粒组成的沉积物。在极性分子（如水）存在下，此类材料的电导率会发生变化。在此，我们提供证据表明，通过在氨（NH₃）存在下进行沉积后电子辐照，在沉积物中掺入氮可以增强与水的相互作用。这为改善和调节通过FEBID制造的湿度传感器的性能开辟了前景。作为概念验证实验，我们通过对三种不同前驱体（即脂肪烃戊烷、简单烯烃（2-甲基-2-丁烯）和潜在的Ru FEBID前驱体双（乙基环戊二烯基）钌（II））的吸附层进行电子辐照，制备了碳质沉积物。在随后的处理步骤中，我们通过对吸附的NH₃进行电子辐照，在沉积物中掺入C-N键。为了测试所得材料的潜在湿度传感能力，我们在沉积物上冷凝了亚单层量的水（H₂O），并评估了它们的热脱附行为。结果证实，H₂O的脱附温度决定性地取决于氮掺入碳质残余物的程度，而这又取决于用于沉积碳质层的前驱体的化学性质。因此，我们预计基于FEBID的湿度传感器的灵敏度可以通过精确计时的沉积后电子和NH₃处理步骤来调节。
