Experimental Study of Diamond Formation in Astrophysical Environments

金刚石代表了碳质宇宙尘埃的主要部分。然而，宇宙金刚石的形成途径还不清楚。本项目致力于研究在类似于星际介质和恒星环境中发现的金刚石形成的条件，包括演化的恒星、原行星和行星环境。该项目包括两个密切相关的部分。在第一部分中，我们将研究碳材料在富含氢的宇宙环境中的侵蚀。我们将在10 K到1400 K的温度范围内研究原子和分子氢对石墨、无定形碳和金刚石材料的刻蚀。这些温度代表了各种天体物理环境中的形成条件。在低温条件下，将使用紫外线照射来促进侵蚀。这些数据将提供关于不同天体物理区域中碳质和金刚石颗粒的化学稳定性的重要信息。在该项目的第二部分，所获得的侵蚀数据将用于寻找合适的金刚石天体物理凝聚条件。氢原子和碳原子是我们宇宙中最丰富的物质，将用于研究金刚石的化学气相沉积过程。金刚石的沉积条件将模拟天体物理条件。碳原子和氢原子流将同时被引导并沉积到适当的衬底上，例如硅晶片或金刚石籽晶。我们将使用一种新开发的原子碳源，它提供了一种强烈而纯净的低能原子碳流。金刚石生长将通过拉曼光谱原位监测。进一步表征的存款将使用红外线，紫外线和可见光吸收光谱，和高分辨率透射电子显微镜。关于天体物理形成条件的实验结果的评价，使我们能够预测有效的金刚石形成和形成途径的天体物理相关网站。

Diamond represents a major part of the carbonaceous cosmic dust. However the formation route of cosmic diamond is not well understood. The present project is devoted to the study of diamond formation at conditions which are similar to those found in the interstellar medium and stellar envelops including evolved stars, protoplanetary, and planetary environments. The project consists of two strongly related tranches. In the first part, we will study the erosion of carbon material in hydrogen-rich, cosmic environments. We will study the etching of graphite, amorphous carbon, and diamond material by atomic and molecular hydrogen at temperatures ranging from 10 K to 1400 K. These temperatures represent the formation conditions in various astrophysical environments. In low-temperature conditions, UV irradiation will be used to facilitate the erosion. These data will provide important information on the chemical stability of carbonaceous and diamond grains in the different astrophysical regions. In the second part of the project, the obtained erosion data will be applied for the finding of appropriate astrophysical condensation conditions of diamond. Atomic hydrogen and carbon, which belong to the most abundant species in our Universe, will be used for the study of the chemical vapor deposition process of diamond. The deposition conditions of diamond will mimic astrophysical conditions. The atomic carbon and hydrogen flows will be simultaneously directed and deposited onto an appropriate substrate such as silicon wafer or diamond seeded crystals. We will use a newly developed atomic carbon source, which provides an intense and pure flux of low-energy atomic carbon. The diamond growth will be monitored in situ by Raman spectroscopy. Further characterization of the deposit will be performed using infrared, ultraviolet, and visible absorption spectroscopy, and high-resolution transmission electron microscopy. The evaluation of the experimental results with regard to astrophysical formation conditions enables us to predict the astrophysically relevant sites of efficient diamond formation and the formation pathways.