Ripple is a common deformation in two-dimensional materials due to localized strain, which is expected to greatly influence the physical properties. The effects of the ripple deformation in the MoS2 layer on their physics, however, are rarely addressed experimentally. We here grow atomically thin MoS2 nanostructures by employing a vapor phase deposition method without any catalyst and observed the ripples in MoS2 nanostructures. The MoS2 ripples exhibit quasi-periodical ripple structures in the MoS2 surface. The heights of the ripples vary from several angstroms to tens of nanometers and the wavelength is in the range of several hundred nanometers. The growth mechanism of rippled MoS2 nanostructures is elucidated. We have also simultaneously investigated the electrostatic properties of MoS2 ripples by using Kelvin probe force microscopy, which shows inhomogeneous surface potential and charge distributions for MoS2 ripple nanostructures with different local strains.

Using the classical molecular dynamics and the simulated annealing techniques, we show that monolayer graphene nanoribbons (GNRs) on 6H-SiC(0001) surface form atomic scale rippled structures. From the analysis of atomic configurations, two different types of rippled structures in GNRs can be identified, namely, the periodic rippled structure at room temperature or even at lower temperatures and random ripples at high temperatures. The dependence of microscopic roughness of the ripples on temperature and size are studied through analyzing the covalent bonding inhomogeneities in bond-length and bond-angle distributions. Our results provide atomic-level information about the rippled GNRs on SiC substrate, which is useful not only for understanding the structure and stability of monolayer GNRs but also for future applications of GNRs in nanoelectronics.

The growth process of graphene structure on 6H-SiC(0001) surface has been studied using the classical molecular dynamics simulation and the simulated annealing technique. Effects of annealing temperature and coverage of carbon atoms on the formation of graphene have been investigated. We found that two layers of carbon atoms of the 6H-SiC(0001) subsurface after sublimation of Si atoms undergo a transformation from a diamondlike phase to a graphenelike structure at annealing temperature above 1500K. This transformation temperature is in good agreement with experimental observations. We also found that the formation of graphene structure strongly depends on the number of carbon layers. Two layers of carbon atoms result in large graphene clusters and four layers of carbon lead to the formation of graphene bilayer sheets. However, a single layer of carbon only forms chainlike and ringlike clusters without the hexagonal ordering. Our results provide atomic-level information about the graphitization of the 6H-SiC(0001) surface, which is useful in controlling the growth of graphene sheets.

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We have investigated the dynamics of dewetting and detachment of nanoscale platinum (Pt) films on graphitic substrates using molecular dynamics (MD). For the thinner Pt nanofilms (<0.6 nm), nanoscale holes are formed randomly during the dewetting process because of the strong interaction between the Pt films and substrate. In contrast, for the thicker Pt nanofilms (>0.6 nm), nanodroplets are formed directly. Interestingly, the nanodroplets can detach from the substrate and the detachment velocity (vd) increases and then decreases as the film gets thicker. We have analyzed the dependence of the detachment velocity on the thickness of the nanofilm by considering the conversion of surface energy to the kinetic energy of a droplet. In addition, the effect of temperature on the dewetting and detachment behavior of the Pt films is also discussed. Our results show that vd increases monotonically with temperature. These results are important for understanding the dewetting and detachment dynamics of metal films on solid substrates.