We experimentally study the morphology of a radially expanding sheet of liquid tin, formed by nanosecond-pulse Nd:YAG laser impact on a spherical microdroplet. Specifically, the sheet thickness profile and its time evolution are captured in detail over a range of laser-pulse energies and for two droplet sizes. Two complementary methods to determine this thickness are employed and shown to be in excellent agreement. All obtained thickness profiles collapse onto a single self-similar curve. Spatial integration of the thickness profiles allows determining the volume of the sheet. Remarkably, less than half of the initial amount of tin remains in the sheet under conditions relevant for industrial sources of extreme ultraviolet light, where these thin tin sheets serve as target material. Further analysis shows that the dominant fraction of the mass lost from the sheet during its expansion ends up as fine fragments. We propose that such mass loss can be minimized by producing the sheet targets on the shortest possible timescale. These findings are particularly valuable for ongoing developments in state-of-the-art nanolithography.

中文翻译：

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拉伸的半透明液态锡片的质量损失

我们实验研究了纳秒脉冲Nd：YAG激光撞击球形微滴形成的液态锡径向扩展片的形态。具体而言，在一定范围的激光脉冲能量和两种液滴尺寸下，将详细记录薄板厚度分布及其时间演变。确定厚度的两种互补方法已被采用，并且显示出极好的一致性。所有获得的厚度轮廓都折叠成一条自相似曲线。厚度轮廓的空间整合可以确定板材的体积。值得注意的是，在与极紫外光的工业光源相关的条件下，锡的初始量中只有不到一半的锡残留，在这些条件下，这些薄锡片用作目标材料。进一步的分析表明，在片材膨胀期间，从片材损失的质量的主要部分最终变成了细小碎片。我们建议可以通过在尽可能短的时间范围内生产薄片目标来最大程度地减少这种质量损失。这些发现对于最新的纳米光刻技术的发展特别有价值。