超短脉冲激光诱导4H-SiC晶体损伤及增长特性及机理的研究

Study on the damage and growth characteristics and mechanism of 4H-SiC crystal induced by ultrashort pulse laser

  • 摘要: 碳化硅(SiC)晶体具备宽带隙、高击穿阈值等一系列优异物理特性,在诸多领域具有重要的应用价值。然而,由于其硬度较高,非接触式加工要求采用具有高峰值强度的超短脉冲激光。本文系统性研究了脉冲持续时间、激光能量及脉冲数量对超短脉冲辐照下不同类别碳化硅材料加工性能的影响。试验结果表明,在单脉冲激光照射条件下,高纯度4H碳化硅(HP-SiC)晶体借助飞秒和皮秒脉冲激光所具有的高峰值强度及极短相互作用时间实现了有效的材料去除;同时,加工后的材料去除面积随脉冲持续时间的增加而显著减小。在氮掺杂4H碳化硅(N-SiC)晶体中,超短脉冲激光加工产生了以随机分布裂纹为特征的烧蚀区,且该区域的演变对脉冲宽度的依赖性较弱。本文还采用能量色散谱(EDS)对各类碳化硅晶体不同损伤区域的化学成分变化进行了详细表征,并进一步探讨了在不同脉冲宽度和脉冲数量条件下激光诱导下HP-SiC及N-SiC晶体表面加工机理。综上,通过对超短脉冲激光作用下碳化硅晶体加工特性的系统性总结,将为制定符合不同碳化硅材料特定需求的加工方案提供参考。

     

    Abstract:
    Background Silicon carbide (SiC) crystal possesses excellent physical properties, including a wide band gap, high breakdown field strength, high thermal conductivity and a low thermal expansion. These attributes make SiC highly valuable for applications in new energy vehicles, power grid equipment, aerospace, and other fields. However, due to its extremely high hardness, traditional contact processing is difficult to meet the processing requirements of high efficiency and high precision.
    Purpose The use of ultra-short pulse laser with high peak intensity has become an effective way to solve this problem. In this paper, the material removal effect and material transformation and spatial distribution of SiC surface irradiated by ultrashort pulse laser under different pulse conditions are studied.
    Methods By systematically adjusting the pulse duration, laser energy and pulse number, the variation of the processing properties of different SiC materials under ultrashort pulse laser irradiation have been revealed. The processing morphology was observed by scanning electron microscopy (SEM), and the material distribution and transformation in different laser irradiation regions were analyzed by energy dispersive spectroscopy (EDS).
    Results The experimental results show that under the irradiation of single pulse laser, the high purity SiC (HP-SiC) crystal achieves effective material removal by relying on the peak intensity and the very short interaction time of femtosecond and picosecond pulse laser, and the material removal area decreases significantly with the increase of pulse duration. After ultrashort pulse laser processing, nitrogen-doped SiC (N-SiC) crystals form an ablation zone characterized by randomly distributed cracks. The evolution of the ablation zone is less dependent on the pulse duration. The chemical composition changes of different irradiated areas of various SiC crystals were characterized in detail by EDS, and the processing mechanisms of laser-induced HP-SiC and N-SiC crystal surfaces under different pulse durations and pulse numbers were further discussed.
    Conclusions In this paper, the processing characteristics of SiC crystals under the irradiation of ultrashort pulse laser are systematically summarized, which can provide reference for the size and ablation effect control of SiC materials.

     

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