Systron Donner Inertial , 2700 Systron Drive, Concord, California 94518, United States.
ACS Nano. 2017 Jun 27;11(6):6139-6145. doi: 10.1021/acsnano.7b02170. Epub 2017 May 22.
A nondestructive scanning near-field thickness resonance acoustic microscopy (SNTRAM) has been developed that provides high-resolution mechanical depth sensitivity and sharp phase contrast of subsurface features. In SNTRAM technology, we excited the sample at its thickness resonance, at which a sharp change in phase is observed and mapped with a scanning probe microscopy stage in near field to provide nanometer-scale nanomechanical contrast of subsurface features/defects. We reported here the remarkable subsubsurface phase contrast and sensitivity of SNTRAM by exciting the sample with a sinusoidal elastic wave at a frequency equal to the thickness resonance of the sample. This results in a large shift in phase component associated with the bulk longitudinal wave propagating through the sample thickness, thus suggesting the usefulness of this method for (a) generating better image contrast due to high S/N of the transmitted ultrasound wave to the other side of the sample and (b) sensitive detection of local variation in material properties at much better resolution due to the sharp change in phase. We demonstrated that the sample excited at the thickness resonance has a more substantial phase contrast and depth sensitivity than that excited at off-resonance and related acoustic techniques. Subsurface features down to 5-8 nm lateral resolution have been demonstrated using a standard sample.
一种无损扫描近场厚度共振声学显微镜 (SNTRAM) 已经被开发出来，它提供了高分辨率的机械深度灵敏度和亚表面特征的锐利相位对比度。在 SNTRAM 技术中，我们在样品的厚度共振处激发样品，在该共振处观察到相位的急剧变化，并通过扫描探针显微镜在近场中进行映射，以提供亚表面特征/缺陷的纳米级纳米机械对比度。我们在这里报告了 SNTRAM 的显著亚表面相位对比度和灵敏度，通过在与样品厚度共振相等的频率下用正弦弹性波激发样品。这导致与穿过样品厚度传播的体纵波相关的相位分量发生大的移动，因此表明该方法在 (a) 由于穿过样品另一侧的超声波的高信噪比产生更好的图像对比度，以及 (b) 由于相位的急剧变化，以更好的分辨率灵敏地检测材料特性的局部变化方面的有用性。我们证明，在厚度共振处激发的样品比在离谐和相关声学技术处激发的样品具有更显著的相位对比度和深度灵敏度。使用标准样品已经证明了可达 5-8nm 横向分辨率的亚表面特征。
