preparation-and-characterization-of-c60graphene-hybrid-nanostructures

Preparation and Characterization of C<sub>60</sub>/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Virginia Tech

We report the preparation of novel quasi-one-dimensional (quasi-1D) C60 nanostructures on rippled graphene. Through careful control of the subtle balance between the linear periodic potential of rippled graphene and the C60 surface mobility, we demonstrate that C60 molecules can be arranged into a quasi-1D C60 chain structure with widths of two to three molecules. At a higher annealing temperature, the quasi-1D chain structure transitions to a more compact hexagonal close packed quasi-1D stripe structure. This first experimental realization of quasi-1D C60 structures on graphene may pave a way for fabricating new C60/graphene hybrid structures for future applications in electronics, spintronics and quantum information. 

Temperature Evolution of Quasi-one-dimensional C60 Nanostructures on Rippled Graphene.

Tensile strain is intrinsic to monolayer crystals of transition metal disulfides such as Mo(W)S grown on oxidized silicon substrates by chemical vapor deposition (CVD) owing to the much larger thermal expansion coefficient of Mo(W)S than that of silica. Here we report fascinating fluorescent variation in intensity with aging time in CVD-grown triangular monolayer WS crystals on SiO (300 nm)/Si substrates and formation of interesting concentric triangular fluorescence patterns in monolayer crystals of large size. The novel fluorescence aging behavior is recognized to be induced by the partial release of intrinsic tensile strain after CVD growth and the induced localized variations or gradients of strain in the monolayer crystals. The results demonstrate that strain has a dramatic impact on the fluorescence and photoluminescence of monolayer WS crystals and thus could potentially be utilized to tune electronic and optoelectronic properties of monolayer transition metal disulfides.

Strain Release Induced Novel Fluorescence Variation in CVD-Grown Monolayer WS Crystals.

In this work we report fabrication and characterization of phenyl-C61-butyric acid methyl ester (PCBM) bilayer structures on graphene and highly oriented pyrolytic graphite (HOPG). Through careful control of the PCBM solution concentration (from 0.1 to 2 mg ml) and the deposition conditions, we demonstrate that PCBM molecules self-assemble into bilayer structures on graphene and HOPG substrates. Interestingly, the PCBM bilayers are formed with two distinct heights on HOPG, but only one unique representative height on graphene. At elevated annealing temperatures, edge diffusion allows neighboring vacancies to merge into a more ordered structure. This is, to the best of our knowledge, the first experimental realization of PCBM bilayer structures on graphene. This work could provide valuable insight into fabrication of new hybrid, ordered structures for applications to organic solar cells.

Self-assembled PCBM bilayers on graphene and HOPG examined by AFM and STM.

To ensure practical applications of atomically thin transition metal dichalcogenides, it is essential to characterize their structural stability under external stimuli such as electric fields and currents. Using vacancy monolayer islands on TiSe surfaces as a model system, we have observed nonlinear area evolution and growth from triangular to hexagonal driven by scanning tunneling microscopy (STM) subjected electrical stressing. The observed growth dynamics represent a 2D departure from the linear area growth law expected for bulk vacancy clustering. Our simulations of monolayer island evolution using phase-field modeling and first-principles calculations are in good agreement with our experimental observations, and point toward preferential edge atom dissociation under STM scanning driving the observed nonlinear area growth. We further quantified a parabolic growth rate dependence with respect to the tunneling current magnitude. The results could be potentially important for device reliability in systems containing ultrathin transition metal dichalcogenides and related 2D materials subject to electrical stressing.

Article	Year
Temperature Evolution of Quasi-one-dimensional C60 Nanostructures on Rippled Graphene. Scientific reports\| PubMed ID: 26391054	2015
Strain Release Induced Novel Fluorescence Variation in CVD-Grown Monolayer WS Crystals. ACS applied materials & interfaces\| PubMed ID: 28902488	2017
Self-assembled PCBM bilayers on graphene and HOPG examined by AFM and STM. Nanotechnology\| PubMed ID: 29451137	2018
Electrical Stressing Induced Monolayer Vacancy Island Growth on TiSe. Nano letters\| PubMed ID: 29461061	2018

Chenggang Tao

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