Experiments and theory are employed to investigate the thermal damage induced by infra-red nanosecond pulses in atmospheric air into a boron-doped diamond target. Micro-Raman spectroscopy, Transmission Electron Microscopy (TEM) analysis and surface topography measurement are used to investigate the carbon phase created during the rapid heating and cooling of diamond, as well as the amount of material ablated during the interaction with the laser. The analysis provides insight into the phenomena occurring for the rapid graphitisation of diamond during pulsed laser ablation, and also the microstructural disorder induced by the thermal and pressure fields at level of energy below and above the melting threshold. To support the understanding from the experimental investigations, a model is constructed for the graphitisation and ablation of diamond coupled with a collisional radiative model for the plasma evolution. The one-dimensional system of non-linear equations that model the physical processes provides an insight into the dynamics of the phenomena leading to the creation of disturbed graphite during pulsed laser ablation. Furthermore, the model helps to identify the main physical processes leading to the creation of disordered graphite, suggesting that plasma evolution does not follow a Boltzmann-Saha equilibrium and that radiative recombination is a main factor influencing the thermal evolution of the plasma and the diamond target. Finally, a good agreement with experimental findings is obtained, particularly in regards to the amount of material ablated, the thickness of the graphite layer and the processes leading to the melting of graphite.

中文翻译：

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金刚石纳秒脉冲激光加工中相变引起的微观结构变化研究

实验和理论被用来研究由红外纳秒脉冲在大气中对掺硼金刚石目标引起的热损伤。显微拉曼光谱、透射电子显微镜 (TEM) 分析和表面形貌测量用于研究金刚石快速加热和冷却过程中产生的碳相，以及与激光相互作用过程中烧蚀的材料量。该分析提供了对脉冲激光烧蚀过程中金刚石快速石墨化发生的现象的深入了解，以及由低于和高于熔化阈值的能量水平的热和压力场引起的微观结构紊乱。为了支持实验研究的理解，为金刚石的石墨化和烧蚀构建了一个模型，并结合了等离子体演化的碰撞辐射模型。对物理过程进行建模的非线性方程的一维系统提供了对导致脉冲激光烧蚀过程中产生受干扰石墨的现象的动力学的洞察。此外，该模型有助于确定导致无序石墨形成的主要物理过程，表明等离子体演化不遵循 Boltzmann-Saha 平衡，并且辐射复合是影响等离子体和金刚石靶材热演化的主要因素. 最后，获得了与实验结果的良好一致性，特别是在烧蚀材料的数量方面，