School of Electrical and Electronic Engineering, Yonsei University , Seoul 03722, Republic of Korea.
Department of Physics, Sogang University , Seoul 04107, Republic of Korea.
Nano Lett. 2017 Dec 13;17(12):7744-7750. doi: 10.1021/acs.nanolett.7b03944. Epub 2017 Nov 20.
We report on the thickness-dependent Raman spectroscopy of ultrathin silicon (Si) nanomembranes (NMs), whose thicknesses range from 2 to 18 nm, using several excitation energies. We observe that the Raman intensity depends on the thickness and the excitation energy due to the combined effects of interference and resonance from the band-structure modulation. Furthermore, confined acoustic phonon modes in the ultrathin Si NMs were observed in ultralow-frequency Raman spectra, and strong thickness dependence was observed near the quantum limit, which was explained by calculations based on a photoelastic model. Our results provide a reliable method with which to accurately determine the thickness of Si NMs with thicknesses of less than a few nanometers.
我们报告了几种激发能下厚度相关的超薄硅（Si）纳米膜（NMs）的喇曼光谱。我们观察到，由于带结构调制的干涉和共振的综合影响，喇曼强度取决于厚度和激发能。此外，在超低频率喇曼光谱中观察到了超薄 Si NMs 中的受限声子模式，并且在量子极限附近观察到了强烈的厚度依赖性，这可以通过基于光弹模型的计算来解释。我们的结果为准确确定厚度小于几纳米的 Si NMs 提供了一种可靠的方法。
