Amorphous structures on metal thin film with a surface of periodicself-organized nanostructures induced by femtosecond laser processing

用透射电镜对铜薄膜进行了结晶度的精确测量。我们分析了在0.08 ~ 0.64 J/cm2的激光能量范围内薄膜上形成光栅结构的电子衍射图。发现晶体结构随激光辐照强度的变化而发生变化；在<0.2 J/cm2时形成多晶结构，在~ 0.23 J/cm2时形成非晶结构，在> 0.35 J/cm2时再次形成多晶结构。从概念上提出了飞秒激光脉冲晶体结构转变的机理，即注入周期结构自形成过程中产生的高能离子诱导晶体结构转变。

The precise measurement for crystaldegree was performed on cupper thin film with transmission electron microscope. We have analyzed the electron diffraction patterns in the laser fluence of 0.08 -0.64 J/cm2where the grating structure is formed on thin films. It is found that the crystal structures are transformed depending on laser fluence; polycrystalline structures at <0.2 J/cm2, amorphous at ~ 0.23 J/cm2, and polycrystalline structures again at > 0.35 J/cm2. The mechanism of crystal structure transformation by femtosecond laser pulses is conceptually proposed, that is induced by the injection of energetic ions generated in the process of self-formation of periodic structures.