3D ripples in a 2D layer

Two-dimensional single layers of carbon atoms known as graphene are thought to be stabilized by 'ripples' that deform the material into three dimensions. Andras Kis and his colleagues at the Swiss Federal Institute of Technology Lausanne (EPFL) report similar structures in molybdenum disulphide.

In the first transmission electron microscopy project to study single layers of MoS₂, the authors show that although the layers have long-range crystalline order, ripples of up to 1 nanometre in height can be observed. The team also identifies differences in the diffraction patterns of single- and multi-layer MoS₂, which could be used to identify single layers. This is the first electron-microscopy study of large MoS₂ sheets known to be just one layer thick. Moreover, MoS₂ is only the second material in which such ripples have been confirmed, say the authors.

Nano Lett. 10.1021/nl2022288 (2011)