Vincent Tom, Hamer Matthew, Grigorieva Irina, Antonov Vladimir, Tzalenchuk Alexander, Kazakova Olga
National Physical Laboratory, Hampton Road, Teddington TW11 0LW, U.K.
Department of Physics, Royal Holloway University of London, Egham TW20 0EX, U.K.
ACS Appl Mater Interfaces. 2020 Dec 23;12(51):57638-57648. doi: 10.1021/acsami.0c19334. Epub 2020 Dec 14.
Graphene has great potential for use in infrared (IR) nanodevices. At these length scales, nanoscale features, and their interaction with light, can be expected to play a significant role in device performance. Bubbles in van der Waals heterostructures are one such feature, which have recently attracted considerable attention, thanks to their ability to modify the optoelectronic properties of two-dimensional (2D) materials through strain. Here, we use scattering-type scanning near-field optical microscopy (sSNOM) to measure the nanoscale IR response from a network of variously shaped bubbles in hexagonal boron nitride (hBN)-encapsulated graphene. We show that within individual bubbles there are distinct domains with strongly enhanced IR absorption. The IR domain boundaries coincide with ridges in the bubbles, which leads us to attribute them to nanoscale strain domains. We further validate the strain distribution in the graphene by means of confocal Raman microscopy and vector decomposition analysis. This shows intricate and varied strain configurations, in which bubbles of different shape induce more bi- or uniaxial strain configurations. This reveals pathways toward future strain-based graphene IR devices.
石墨烯在红外（IR）纳米器件中具有巨大的应用潜力。在这些长度尺度下，纳米级特征及其与光的相互作用有望在器件性能中发挥重要作用。范德华异质结构中的气泡就是这样一种特征，由于它们能够通过应变改变二维（2D）材料的光电特性，最近受到了相当大的关注。在这里，我们使用散射型扫描近场光学显微镜（sSNOM）来测量六方氮化硼（hBN）封装的石墨烯中各种形状气泡网络的纳米级红外响应。我们表明，在单个气泡内存在具有强烈增强红外吸收的不同区域。红外区域边界与气泡中的脊重合，这使我们将它们归因于纳米级应变区域。我们通过共聚焦拉曼显微镜和矢量分解分析进一步验证了石墨烯中的应变分布。这显示了复杂多样的应变构型，其中不同形状的气泡会诱导更多的双轴或单轴应变构型。这揭示了未来基于应变的石墨烯红外器件的发展途径。
