Dynamics and mechanism of discrete etching of organic materials by femtosecond laser excitation
Dynamics and mechanism of discrete etching of organic materials by femtosecond laser excitation
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飞秒激光激发有机材料离散刻蚀动力学及机理
DOI：
10.1117/12.432499
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
H. Masuhara
中科院分区：
文献类型：
--
作者：
Y. Hosokawa;Masaki Yashiro;T. Asahi;H. Masuhara
采用780 nm钛宝石激光器，通过改变脉冲宽度（170 fs，250 ps，100 ns），研究了微晶铜酞菁薄膜的激光烧蚀和刻蚀。高于fs（40 mJ/cm 2）和ps（50 mJ/cm 2）烧蚀阈值，蚀刻深度变得恒定，几乎是独立的激光能量密度，并在fs能量密度的进一步增加的结果在完全去除的膜。我们将这种独特的烧蚀现象命名为离散刻蚀。另一方面，由ns激光激发的蚀刻深度随着能量密度的增加而逐渐增加，超过其烧蚀阈值（80 mJ/cm 2）。为了揭示fs和ns刻蚀行为之间的差异，我们分别用时间分辨吸收光谱和时间分辨表面散射成像直接测量了激发能量弛豫和表面形貌变化。从强飞秒激光激发到分步刻蚀的时间演化过程中，研究了飞秒激光的离散刻蚀现象及其机理。在此基础上，我们提出了飞秒激光烧蚀模型，即应力的超快增加导致机械破坏，从而导致离散的刻蚀行为。
Laser ablation and etching of microcrystalline Cu- phthalocyanine thin films were examined by changing pulse duration (170 fs, 250 ps, 100 ns) of a 780 nm Ti:sapphire laser. Above fs (40 mJ/cm2) and ps (50 mJ/cm2) ablation thresholds, the etch depth becomes constant and is almost independent of laser fluence, and further increase in the fs fluence results in complete removal of the film. We name the unique ablation phenomenon discrete etching. On the other hand, the depth etched by ns laser excitation increases gradually with the fluence above its ablation threshold (80 mJ/cm2. In order to reveal the difference between the fs and ns etching behaviors, we measured directly excitation energy relaxation and surface morphology change with time-resolved absorption spectroscopy and time- resolved surface scattering imaging, respectively. The fs discrete etching phenomenon and its mechanism were considered in view of time evolutions from highly intense fs laser excitation to the step-wise etching. On the basis of the results, we propose an fs laser ablation model that ultrafast stress increase brings about mechanical disruption leading to the discrete etching behavior.