It is challenging to selectively remove a thin film with a high melting temperature from an underlying one with a low melting temperature where precise stops at layer interfaces are required. In this study, an ultrashort laser pulse is used to cleanly ablate a 40 nm thin molybdenum layer from an aluminium thin film in a commercially relevant heterostructure. We observe clean delamination of molybdenum from aluminium. We observe that columnar nanostructures in Mo are generated well below the damage threshold fluence. Both delamination and nanostructure formation are considered in terms of electromechanical forces. At low fluence, only selective removal of the very near surface of the Mo thin film was observed. At higher fluences, ablation of the Mo film occurred without melting of the underlying Al layer. Our computational results confirm the important role of thermionic electron emission and near surface electron-phonon coupling in nanostructure generation. We introduce a thermal boundary resistance effect in the heat diffusion by electrons to more accurately describe the release of the Mo from the Al layer. The comparison of experimental and simulation results confirms that electromechanical stresses can be an important mechanism in selective thin film ablation.

从需要在层界面处精确停止的具有低熔化温度的底层薄膜选择性地去除具有高熔化温度的薄膜是具有挑战性的。在这项研究中，超短激光脉冲用于从商业相关异质结构中的铝薄膜上干净地烧蚀 40 nm 薄钼层。我们观察到钼与铝的干净分层。我们观察到 Mo 中的柱状纳米结构远低于损伤阈值注量。从机电力的角度考虑分层和纳米结构的形成。在低通量下，仅观察到 Mo 薄膜非常近表面的选择性去除。在更高的能量密度下，Mo 膜的烧蚀发生而不熔化下面的 Al 层。我们的计算结果证实了热电子发射和近表面电子-声子耦合在纳米结构生成中的重要作用。我们在电子的热扩散中引入了热边界电阻效应，以更准确地描述 Mo 从 Al 层的释放。实验和模拟结果的比较证实，机电应力可能是选择性薄膜烧蚀的重要机制。