利用STM 直接观察红荧烯薄膜中的质量密度波
摘要
Strain plays a crucial role in controlling the structure and morphology of heteroepitaxial films. Theoretical study predicted that, in the incommensurate films, strain can be released by creating of mass density wave (MDW). However, there has been so far no conclusive evidence for the existence of MDW. Here we show the direct observation of MDW in rubrene monolayer grown on Bi(001) using scanning tunnelling microscopy (STM). It is found that MDWs manifest themselves as small sinusoidal variation of surface height, plus periodic distortion of molecular orientations. Furthermore, we demonstrate that the MDW formation results from lattice rotation of rubrene monolayer with respect to Bi substrate. Depending on the rotational direction, MDW may exhibit either stripe or zigzag patterns.