Photothermal excitation of the cantilever for use in subsurface imaging with atomic force microscopy was compared against traditional piezoelectric excitation. Photothermal excitation alleviates issues commonly found in traditional piezoelectrics such as spurious resonances by producing clean resonance peaks through direct cantilever excitation. A calibration specimen consisting of a 3 × 3 array of holes ranging from 200 to 30 nm etched into silicon and covered by graphite was used to compare these two drive mechanisms. Photothermal excitation exhibited a signal-to-noise ratio as high as four times when compared to piezoelectric excitation, utilizing higher eigenmodes for subsurface imaging. The cleaner and sharper resonance peaks obtained using photothermal excitation revealed all subsurface holes down to 30 nm through 135 nm of graphite. In addition, we demonstrated the ability of using photothermal excitation to detect the contact quality variation and evolution at graphite-polymer interfaces, which is critical in graphene-based nanocomposites, flexible electronics, and functional coatings.

中文翻译：

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通过原子力显微镜中的光热激发增强纳米级次表面成像的灵敏度

将悬臂的光热激发用于原子力显微镜下的成像与传统的压电激发进行了比较。光热激发通过直接悬臂激发产生干净的共振峰，缓解了传统压电材料中常见的问题，例如虚假共振。校准样品由 200 至 30 nm 的 3 × 3 孔阵列组成，这些孔蚀刻到硅中并被石墨覆盖，用于比较这两种驱动机制。与压电激发相比，光热激发的信噪比高达四倍，利用更高的本征模式进行地下成像。使用光热激发获得的更清晰、更清晰的共振峰揭示了石墨的所有地下孔洞，直径低至 30 纳米至 135 纳米。