Electrical Engineering, ‡Chemical and Biomolecular Engineering, Case School of Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.
Nano Lett. 2017 Aug 9;17(8):4568-4575. doi: 10.1021/acs.nanolett.7b00730. Epub 2017 Jul 6.
Emerging atomic layer semiconducting crystals such as molybdenum disulfide (MoS) are promising candidates for flexible electronics and strain-tunable devices due to their ultrahigh strain limits (up to ∼20-30%) and strain-tunable bandgaps. However, high strain levels, controllable isotropic and anisotropic biaxial strains in single- and few-layer MoS on device-oriented flexible substrates permitting convenient and fast strain tuning, remain unexplored. Here, we demonstrate a "blown-bubble" bulge technique for efficiently applying large strains to atomic layer MoS devices on a flexible substrate. As the strain increases via bulging, we achieve continuous tuning of Raman and photoluminescence (PL) signatures in single- and few-layer MoS, including splitting of Raman peaks. With proper clamping of the MoS crystals, we apply up to ∼9.4% strain in the flexible substrate, which causes a doubly clamped single-layer MoS to fracture at 2.2-2.6% strain measured by PL and 2.9-3.5% strain measured by Raman spectroscopy. This study opens new pathways for exploiting 2D semiconductors on stretchable substrates for flexible electronics, mechanical transducers, tunable optoelectronics, and biomedical transducers on curved and bulging surfaces.
新兴的原子层半导体晶体，如二硫化钼 (MoS)，由于其超高的应变极限（高达 ∼20-30%）和应变可调带隙，是柔性电子和应变可调设备的有前途的候选材料。然而，在面向器件的柔性衬底上的单原子层和少层 MoS 中实现高应变水平、可控各向同性和各向异性双轴应变，以及方便和快速的应变调谐，仍有待探索。在这里，我们展示了一种“吹泡泡”凸包技术，用于有效地在柔性衬底上对原子层 MoS 器件施加大应变。随着凸包应变的增加，我们实现了单原子层和少层 MoS 中 Raman 和光致发光（PL）特征的连续调谐，包括 Raman 峰的劈裂。通过适当的 MoS 晶体夹紧，我们在柔性衬底中施加高达 ∼9.4%的应变，这导致在 PL 测量的 2.2-2.6%应变和 Raman 光谱测量的 2.9-3.5%应变下，双夹单原子层 MoS 断裂。这项研究为在可拉伸衬底上开发二维半导体开辟了新途径，可用于柔性电子、机械换能器、可调谐光电子学和弯曲和凸包表面的生物医学换能器。
