This paper presents a previously unreported mechanism for the formation of High Spatial Frequency Laser Induced Periodic Surface Structures (HSFL) in GaAs upon irradiation by femtosecond laser pulses (repetition rate = 1 kHz, τ = 150 fs, λ = 390 nm) that is driven by point defect diffusion, desorption of surface atoms, and roughening of the surface. The HSFL have trenches that are 100 nm deep, an average spatial period of 65 nm, and are completely below the original surface. Sub-100 nm periodicity with high depth to period aspect ratio has not been previously observed in GaAs. In the proposed mechanism, laser irradiation generates point defects that diffuse to the surface. Interstitials that reach the surface can be easily desorbed and the remaining vacancies coalesce into vacancy islands. This results in a rough surface, which can excite surface plasmon polaritons. Despite our observations of periodicity corresponding to SPPs, calculations done using the excited dielectric function indicate that SPPs should not be supported. This points to the need to incorporate the cumulative effects of laser irradiation in existing models. This paper also presents evidence that desorption can also occur during HSFL formation in GaAs when irradiated with 780 nm in vacuum. The HSFL have the similar spatial period as GaAs irradiated in air with 780 nm, but completely below the original surface.

中文翻译：

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由飞秒激光诱导的 GaAs 解吸驱动的亚 100 nm 高空间频率周期结构

本文提出了一种以前未报道的机制，用于在飞秒激光脉冲（重复率 = 1 kHz，τ  = 150 fs，λ）照射下在 GaAs 中形成高空间频率激光诱导周期表面结构 (HSFL) = 390 nm），这是由点缺陷扩散、表面原子解吸和表面粗糙化驱动的。HSFL 具有 100 nm 深的沟槽，平均空间周期为 65 nm，并且完全低于原始表面。以前在 GaAs 中没有观察到具有高深度周期纵横比的亚 100 nm 周期性。在所提出的机制中，激光照射会产生扩散到表面的点缺陷。到达表面的间隙很容易解吸，剩余的空位合并成空位岛。这导致粗糙的表面，可以激发表面等离子体激元。尽管我们观察到与 SPP 对应的周期性，但使用激发的介电函数进行的计算表明不应支持 SPP。这表明需要在现有模型中纳入激光照射的累积效应。本文还提供了证据，表明在真空中用 780 nm 辐照时，GaAs 中 HSFL 形成过程中也会发生解吸。HSFL 的空间周期与在空气中照射 780 nm 的 GaAs 相似，但完全低于原始表面。