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利用10倍的显微物镜将近红外飞秒激光脉冲汇聚到宽带隙半导体材料6H SiC的前表面,研究样品的烧蚀及诱导微细结构。用扫描电镜(Scanning electron microscope,SEM)及光学显微镜测量烧蚀斑。利用烧蚀面积与激光脉冲能量的关系确定SiC的烧蚀阈值。给出了SiC样品的烧蚀阈值与飞秒激光波长的依赖关系。实验结果表明,可见光区随波长增加,烧蚀阈值从0.29J/cm2增加到0.67J/cm2;而在近红外区,SiC的烧蚀阈值为0.70J/cm2左右,基本上不随激光波长变化而改变。结合计算结果,可以认为在飞秒激光烧蚀SiC的过程中,在近红外区,光致电离和碰撞电离均起到了重要的作用;而在可见光区,光致电离的作用相对大一些。
The near-infrared femtosecond laser pulse was focused on the front surface of a wide bandgap semiconductor material 6H SiC by using a 10x microscope and the ablation of the sample and the induction of fine structure were investigated. Ablation spots were measured by scanning electron microscope (SEM) and optical microscope. The ablation threshold of SiC was determined by the relationship between the ablation area and the laser pulse energy. The dependence of ablation threshold of SiC samples on the wavelength of femtosecond laser is given. The experimental results show that the visible light region increases with wavelength, and the ablation threshold increases from 0.29J / cm2 to 0.67J / cm2. In the near infrared region, the ablation threshold of SiC is about 0.70J / cm2, which is basically unchanged with the laser wavelength change. Combining with the calculation results, it can be concluded that during the femtosecond laser ablation of SiC, photoionization and collision ionization play an important role in the near infrared region. In the visible region, photoionization is relatively large.