Department of Applied Physics, Yale University , New Haven, Connecticut 06511, United States.
Energy Sciences Institute, Yale University , West Haven, Connecticut 06516, United States.
Nano Lett. 2017 Mar 8;17(3):1582-1586. doi: 10.1021/acs.nanolett.6b04729. Epub 2017 Feb 10.
Helium ion beams (HIB) focused to subnanometer scales have emerged as powerful tools for high-resolution imaging as well as nanoscale lithography, ion milling, or deposition. Quantifying irradiation effects is an essential step toward reliable device fabrication, but most of the depth profiling information is provided by computer simulations rather than the experiment. Here, we demonstrate the use of atomic force microscopy (AFM) combined with scanning near-field optical microscopy (SNOM) to provide three-dimensional (3D) dielectric characterization of high-temperature superconductor devices fabricated by HIB. By imaging the infrared dielectric response obtained from light demodulation at multiple harmonics of the AFM tapping frequency, we find that amorphization caused by the nominally 0.5 nm HIB extends throughout the entire 26.5 nm thickness of the cuprate film and by ∼500 nm laterally. This unexpectedly widespread damage in morphology and electronic structure can be attributed to a helium depth distribution substantially modified by the internal device interfaces. Our study introduces AFM-SNOM as a quantitative tomographic technique for noninvasive 3D characterization of irradiation damage in a wide variety of nanoscale devices.
氦离子束（HIB）聚焦到亚纳米尺度，已成为高分辨率成像以及纳米尺度光刻、离子铣削或沉积的有力工具。量化辐照效应是可靠器件制造的重要步骤，但大多数深度剖析信息是由计算机模拟提供的，而不是实验。在这里，我们展示了原子力显微镜（AFM）与扫描近场光学显微镜（SNOM）的结合，用于对 HIB 制造的高温超导器件进行三维（3D）介电特性的研究。通过对 AFM 轻敲频率多个谐波的光解调获得的红外介电响应进行成像，我们发现，名义上 0.5nm 的 HIB 引起的非晶化延伸到整个 26.5nm 厚的铜酸盐薄膜中，并向两侧延伸了约 500nm。这种在形态和电子结构上出乎意料的广泛损伤可归因于内部器件界面显著改变了氦的深度分布。我们的研究引入了 AFM-SNOM，作为一种定量层析技术，用于对各种纳米器件中的辐照损伤进行非侵入式 3D 特性研究。
