Comparison of ablation mechanisms at low fluence for ultrashort and short-pulse laser exposure of very thin molybdenum films on glass.
Comparison of ablation mechanisms at low fluence for ultrashort and short-pulse laser exposure of very thin molybdenum films on glass.
复制标题
玻璃上极薄钼薄膜超短和短脉冲激光曝光低能量密度下烧蚀机制的比较。
DOI：
10.1364/ao.55.002117
复制
发表时间：
2016
期刊：
影响因子：
1.9
通讯作者：
G. O'Connor
中科院分区：
文献类型：
--
作者：
Pinaki Das Gupta;G. O'Connor
研究了飞秒和纳秒激光在不同波长下从玻璃基板上完全去除松散粘附的极薄钼膜。原子力显微镜和扫描电子显微镜证实，飞秒脉冲对钼膜的烧蚀发生在接近损伤阈值的范围内，对衬底的损伤最小。这与纳秒激光加工相反，在等效损伤阈值范围内观察到明显的衬底损伤。模拟预测了飞秒情况下的两阶段机械屈曲机制。面外热膨胀首先导致钼膜从玻璃基板上拉伸膨胀；这种局部分层的薄膜随后被压应力屈曲，导致薄膜剥落。纳秒激光脉冲的烧蚀行为不同。在纳秒的情况下，观察到钼中明显的热扩散长度（~ 700 nm）导致玻璃的热膨胀增加。熔融玻璃产生的热诱导应力产生了一个分层区域，将压缩膜“推”离基板。这些发现与未来极薄钼层的选择性激光图案化有关。
Complete removal of a loosely adhered very thin molybdenum film from a glass substrate is investigated for both femtosecond and nanosecond lasers at different wavelengths. Atomic force microscopy and scanning electron microscopy confirm that ablation of the molybdenum film by femtosecond pulses occurs close to the damage threshold fluence, creating minimal damage to the substrate. This is in contrast to nanosecond laser processing where significant substrate damage at the equivalent damage threshold fluence is observed. Simulations predict a two-stage mechanical buckling mechanism in the femtosecond case. Out-of-plane thermal expansion first results in a tensile expansion of molybdenum film from the glass substrate; this locally delaminated film is then buckled by a subsequent compressive stress, leading to thin film spallation. Ablation by nanosecond laser pulses behaves differently. The appreciable heat diffusion length (∼700 nm) in molybdenum, observed for the nanosecond case, results in an increased thermal expansion of the glass. The thermally induced stress generated by the molten glass creates a delaminated area, which "pushes" the compressed film away from the substrate. These findings are relevant to future selective laser patterning of very thin molybdenum layers.