Sedelnikova Olga V, Fedoseeva Yuliya V, Gorodetskiy Dmitriy V, Palyanov Yuri N, Shlyakhova Elena V, Maksimovskiy Eugene A, Makarova Anna A, Bulusheva Lyubov G, Okotrub Aleksandr V
Nikolaev Institute of Inorganic Chemistry, SB RAS, 630090 Novosibirsk, Russia.
Sobolev Institute of Geology and Mineralogy, SB RAS, 630090 Novosibirsk, Russia.
Beilstein J Nanotechnol. 2025 Jun 12;16:887-898. doi: 10.3762/bjnano.16.67. eCollection 2025.
Controlling high-temperature graphitization of diamond surfaces is important for many applications, which require the formation of thin conductive electrodes on dielectric substrates. Transition metal catalysts can facilitate the graphitization process, which depends on the diamond face orientation. In the present work, the role of a nickel coating on the electronic structure and chemical state of graphite layers formed on the surface of a polycrystalline diamond (PCD) film with mixed grain orientation was studied. A synthetic single-crystal diamond (SCD) with a polished (110) face was examined for comparison. The samples were coated with a thin nickel film deposited by thermal evaporation. The graphitization of diamond with and without a nickel coating as a result of high-vacuum annealing at a temperature of about 1100 °C was studied in situ using synchrotron-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) methods. XPS data revealed the formation of a thin graphite-like film with low-ordered atomic structure on the surface of the nickel-coated PCD film. The chemical state of sp-hybridized carbon atoms was found to be insensitive to the face orientation of the diamond micro-sized crystallites; however, the layer defectiveness increased in areas with fine-dispersed crystallites. According to NEXAFS and Raman spectroscopy data, the most ordered atomic structure of graphitic layers was obtained by annealing nickel-coated SCD. The angular dependence of NEXAFS C K-edge spectra of nickel-coated (110) face after annealing discovered the vertical orientation of sp-hybridized carbon layers relative to the diamond surface. The observed behavior suggests that sp carbon layers were formed on the diamond surface due to its saturation by released carbon atoms as a result of etching by nickel.
控制金刚石表面的高温石墨化对于许多应用都很重要，这些应用需要在介电基板上形成薄的导电电极。过渡金属催化剂可以促进石墨化过程，而这一过程取决于金刚石的晶面取向。在本工作中，研究了镍涂层对具有混合晶粒取向的多晶金刚石（PCD）薄膜表面形成的石墨层的电子结构和化学状态的作用。为作比较，还研究了具有抛光（110）面的合成单晶金刚石（SCD）。通过热蒸发在样品上沉积了一层薄镍膜。使用基于同步加速器的X射线光电子能谱（XPS）和近边X射线吸收精细结构（NEXAFS）方法，原位研究了在约1100°C温度下高真空退火后有和没有镍涂层的金刚石的石墨化情况。XPS数据表明，在镀镍的PCD薄膜表面形成了具有低序原子结构的薄石墨状薄膜。发现sp杂化碳原子的化学状态对金刚石微晶的晶面取向不敏感；然而，在微晶细分散的区域，层缺陷增加。根据NEXAFS和拉曼光谱数据，通过对镀镍的SCD进行退火获得了石墨层最有序的原子结构。退火后镀镍（110）面的NEXAFS C K边光谱的角度依赖性发现，sp杂化碳层相对于金刚石表面呈垂直取向。观察到的行为表明，由于镍蚀刻释放的碳原子使金刚石表面饱和，从而在金刚石表面形成了sp碳层。
