Experimental Study of Diamond Formation in Astrophysical Environments

钻石代表了碳质宇宙尘埃的主要部分。然而，宇宙钻石的形成路线尚不清楚。本项目致力于研究在类似于星际介质和恒星包层的条件下形成的钻石，包括演化的恒星、原行星和行星环境。该项目由两个紧密相关的部分组成。在第一部分中，我们将研究富氢宇宙环境中碳物质的侵蚀。我们将研究石墨、非晶碳和金刚石材料在10 ~ 1400 K温度下的原子和分子氢蚀刻。这些温度代表了不同天体物理环境下的形成条件。在低温条件下，将使用紫外线照射来促进侵蚀。这些数据将为不同天体物理区域的碳质和金刚石颗粒的化学稳定性提供重要信息。在项目的第二部分，获得的侵蚀数据将用于寻找合适的金刚石天体物理凝结条件。原子氢和原子碳是我们宇宙中最丰富的物质，它们将被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。原子碳和氢的流动将同时定向并沉积在适当的衬底上，如硅片或金刚石种子晶体。我们将使用一种新开发的原子碳源，它能提供强烈而纯净的低能原子碳通量。利用拉曼光谱对金刚石生长进行现场监测。将使用红外、紫外和可见吸收光谱以及高分辨率透射电子显微镜对该矿床进行进一步表征。对天体物理形成条件的实验结果进行评价，使我们能够预测有效钻石形成的天体物理相关地点和形成途径。

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.