Scattering-controlled femtosecond-laser induced nanostructuring of TiO2 thin films
Scattering-controlled femtosecond-laser induced nanostructuring of TiO2 thin films
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DOI：
10.1117/12.874519
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发表时间：
2011-02
期刊：
影响因子：
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通讯作者：
S. Das;A. Rosenfeld;M. Bock;A. Pfuch;W. Seeber;R. Grunwald
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作者：
S. Das;A. Rosenfeld;M. Bock;A. Pfuch;W. Seeber;R. Grunwald
激光诱导周期性表面结构（LIPSS）的形成在很大程度上具有自组织性质，并且在其早期阶段基本上受光散射的影响。然而，相关机制的演变仍有待详细研究，并强烈依赖于材料和激光参数。用高强度超短脉冲激发，由于开放的多光子激发通道，导致产生周期远低于基本波长的纳米波纹结构。由于这种激光诱导周期性纳米结构（LIPNS）的空间尺度急剧减小，在这种特殊情况下，预计散射的特殊影响。在这里，我们报告的第一次调查的飞秒激光诱导溅射二氧化钛（TiO 2）层的纳米结构相比，散装材料。研究了光学膜质量对LIPNS形貌的影响。对于800 nm的激发波长，发现纳米波纹的典型周期在80-180 nm的范围内。与我们以前报道的结果散装二氧化钛，LIPNS薄膜优先出现在低脉冲数（N=5-20）。这一观察结果解释了由薄膜结构和界面引起的散射中心的数量较高。基本假设得到进一步支持的补充实验与抛光和未抛光表面的散装二氧化钛单晶。
The formation of laser induced periodic surface structures (LIPSS) is to a large extent of self-organizing nature and in its early stages essentially influenced by optical scattering. The evolution of related mechanisms, however, has still to be studied in detail and strongly depends on materials and laser parameters. Excitation with highly intense ultrashort pulses leads to the creation of nanoripple structures with periods far below the fundamental wavelength because of opening multiphoton excitation channels. Because of the drastically reduced spatial scale of such laser induced periodic nanostructures (LIPNS), a particular influence of scattering is expected in this special case. Here we report on first investigations of femtosecond-laser induced nanostructuring of sputtered titanium dioxide (TiO2) layers in comparison to bulk material. The crucial role of the optical film quality for the morphology of the resulting LIPNS was worked out. Typical periods of nanoripples were found to be within the range of 80-180 nm for an excitation wavelength of 800 nm. Unlike our previously reported results on bulk TiO2, LIPNS in thin films appeared preferentially at low pulse numbers (N=5-20). This observation was explained by a higher number of scattering centers caused by the thin film structure and interfaces. The basic assumptions are further supported by supplementary experiments with polished and unpolished surfaces of bulk TiO2 single crystals.