Holleufer Steffen Friis, Hopkinson Alfred T, Sutherland Duncan S, Li Zheshen, Lauritsen Jeppe V, Hornekaer Liv, Cassidy Andrew
Center for Interstellar Catalysis, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark.
Phys Chem Chem Phys. 2025 Jul 2;27(26):13906-13916. doi: 10.1039/d5cp01089f.
Nanoscale silicate dust particles are the most abundant refractory component observed in the interstellar medium and are thought to play a key role in catalysing the formation of complex organic molecules in the star forming regions of space. We present a method to synthesise a laboratory analogue of nanoscale silicate dust particles on highly oriented pyrolytic graphite (HOPG) substrates by co-deposition of the atomic constituents. The resulting nanoparticulate films are sufficiently thin and conducting to allow for surface science investigations, and are characterised here, under UHV, using X-ray photoelectron spectroscopy, near-edge X-ray absorption atomic fine spectroscopy and scanning tunnelling microscopy, and, , using scanning electron microscopy. We compare SiO film growth with and without the use of atomic O beams during synthesis and conclude that exposure of the sample to atomic O leads to homogeneous films of interconnected nanoparticle networks. The networks cover the graphite substrate and demonstrate superior thermal stability, up to 1073 K, when compared to oxides produced without exposure to atomic O. In addition, control over the flux of atomic O during growth allows for control of the average oxidation state of the film produced. Photoelectron spectroscopy measurements demonstrate that fully oxidised films have an SiO stoichiometry very close to bulk SiO and scanning tunnelling microscopy images show the basic cluster building unit to have a radius of approximately 2.5 nm. The synthesis of SiO films with adjustable stoichiometry and suitable for surface science experiments that require conducting substrates will be of great interest to the astrochemistry community, and will allow for nanoscale-investigation of the chemical processes thought to be catalysed at the surface of dust grains in space.
纳米级硅酸盐尘埃颗粒是在星际介质中观测到的最丰富的难熔成分，被认为在催化空间恒星形成区域中复杂有机分子的形成过程中起着关键作用。我们提出了一种通过原子成分共沉积在高度取向热解石墨（HOPG）衬底上合成纳米级硅酸盐尘埃颗粒实验室模拟物的方法。所得的纳米颗粒薄膜足够薄且具有导电性，便于进行表面科学研究，本文在超高真空（UHV）条件下，使用X射线光电子能谱、近边X射线吸收原子精细光谱和扫描隧道显微镜对其进行了表征，此外还使用了扫描电子显微镜。我们比较了合成过程中使用和不使用原子氧束时SiO薄膜的生长情况，得出结论：样品暴露于原子氧会导致形成相互连接的纳米颗粒网络的均匀薄膜。与未暴露于原子氧而产生的氧化物相比，这些网络覆盖了石墨衬底，并表现出高达1073 K的卓越热稳定性。此外，在生长过程中控制原子氧的通量可以控制所制备薄膜的平均氧化态。光电子能谱测量表明，完全氧化的薄膜具有非常接近块状SiO的SiO化学计量比，扫描隧道显微镜图像显示基本的团簇构建单元半径约为2.5 nm。合成具有可调化学计量比且适用于需要导电衬底的表面科学实验的SiO薄膜，将引起天体化学界的极大兴趣，并将允许对被认为在空间尘埃颗粒表面催化的化学过程进行纳米级研究。
