Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

Two-dimensional Fullerene-Based Ferroelectric Materials: Assembly and Effects on Charge Carrier Lifetime

Manipulating the symmetry of fullerene-based low-dimensional materials is crucial to the development of electronic devices and modern nonvolatile memories. However, there have been few reports on studying the physicochemical properties of fullerene and its derivatives by controlling the symmetries. Herein, we demonstrate ferroelectricity in Sc3N@Ih-C80-Pd/Pt adducts with relatively strong spontaneous polarization. Polarization originates from subtle molecular interactions between Sc3N@Ih-C80 and Pd/Pt atoms, breaking the structural symmetry. Additionally, we investigate how a temperature-dependent polar-nonpolar phase transition affects the corresponding nonadiabatic electron-hole recombination process in the ferroelectric fullerene adduct Sc3N@Ih-C80-Pd. The results indicate that polarization has a greater impact than temperature effects, resulting in an extension of the carrier lifetime in the polar phase by over 3 times compared to that in the nonpolar phase. Our findings unveil new members of the ferroelectric fullerene family and provide guidance for improving the performance of optoelectronic materials.

Assembly-inspired multiferroicity with nontrivial Chern insulating phase from exohedral metallofullerenes

Fullerene-assembled low-dimensional materials have been experimentally realized in polymorphic forms and have attracted significant interest very recently. Here, we predict a two-dimensional (2D) honeycomb lattice material TM2(C60)3 (TM = Cr, Mo, and W) assembled from exohedral metallofullerene clusters TM(C60)3 that could exhibit planar triangular geometries. According to first-principles calculations combined with Monte Carlo simulations, we suggest that these 2D assembled materials exhibit various exotic physical properties, including ferromagnetism, ferroelectricity, and quantum anomalous Hall effect. Interestingly, mechanical strains could effectively tune their magnetic moments and switch the conducting spin channel of the Dirac bands at the Fermi level. Our work provides a new cluster-assembly design strategy toward cluster-assembled 2D materials based on fullerene characters.

Direct CVD Growth of Graphene on Technologically Important Dielectric and Semiconducting Substrates

To fabricate graphene based electronic and optoelectronic devices, it is highly desirable to develop a variety of metal-catalyst free chemical vapor deposition (CVD) techniques for direct synthesis of graphene on dielectric and semiconducting substrates. This will help to avoid metallic impurities, high costs, time consuming processes, and defect-inducing graphene transfer processes. Direct CVD growth of graphene on dielectric substrates is usually difficult to accomplish due to their low surface energy. However, a low-temperature plasma enhanced CVD technique could help to solve this problem. Here, the recent progress of metal-catalyst free direct CVD growth of graphene on technologically important dielectric (SiO2, ZrO2, HfO2, h-BN, Al2O3, Si3N4, quartz, MgO, SrTiO3, TiO2, etc.) and semiconducting (Si, Ge, GaN, and SiC) substrates is reviewed. High and low temperature direct CVD growth of graphene on these substrates including growth mechanism and morphology is discussed. Detailed discussions are also presented for Si and Ge substrates, which are necessary for next generation graphene/Si/Ge based hybrid electronic devices. Finally, the technology development of the metal-catalyst free direct CVD growth of graphene on these substrates is concluded, with future outlooks.

X3 synthon geometries in two-dimensional halogen-bonded 1,3,5-tris(3,5-dibromophenyl)benzene self-assembled nanoarchitectures on Au(111)-()

The self-assembly of star-shaped 1,3,5-tris(3,5-dibromophenyl)benzene molecules on Au(111)-() in a vacuum is investigated using scanning tunneling microscopy and core-level spectroscopy. Scanning tunneling microscopy shows that the molecules self-assemble into a hexagonal porous halogen-bonded nanoarchitecture. This structure is stabilized by X_3-A synthons composed of three type-II halogen-interactions (halogen-bonds). The molecules are oriented along the same direction in this arrangement. Domain boundaries are observed in the hcp region of the herringbone gold surface reconstruction. Molecules of the neighboring domains are rotated by 180°. The domain boundaries are stabilized by the formation of X_3-B synthons composed of two type-II and one type-I halogen-interactions between molecules of the neighboring domains. Core-level spectroscopy confirms the existence of two types of halogen-interactions in the organic layer. These observations show that the gold surface reconstructions can be exploited to modify the long-range supramolecular halogen-bonded self-assemblies.

Direct growth of high-quality graphene on high-κ dielectric SrTiO₃ substrates

High-quality monolayer graphene was synthesized on high-κ dielectric single crystal SrTiO3 (STO) substrates by a facile metal-catalyst-free chemical vapor deposition process. The as-grown graphene sample was suitable for fabricating a high performance field-effect transistor (FET), followed by a far lower operation voltage compared to that of a SiO2-gated FET and carrier motilities of approximately 870-1050 cm(2)·V(-1)·s(-1) in air at rt. The directly grown high-quality graphene on STO makes it a perfect candidate for designing transfer-free, energy-saving, and batch production of FET arrays.

NaCl multi-layer islands grown on Au(111)-([Formula: see text]) probed by scanning tunneling microscopy

The growth of multi-layer NaCl islands on Au(111)-([Formula: see text]) surfaces was investigated using scanning tunneling microscopy (STM). We observed that the aspect of the NaCl islands drastically differs depending on the tunneling conditions. It is therefore possible to observe the layers forming an NaCl island or to image the gold reconstruction below the first NaCl layer. Atomically resolved STM images obtained on the first NaCl layer demonstrate that NaCl grows as an epitaxial crystalline film on Au(111)-([Formula: see text]). STM images also suggest that some NaCl layers can be non-crystalline.

C70 ordering on nanostructured SrTiO3(001)

The nanostructured (7 x 4) surface of SrTiO(3)(001) is used as a template to order C(70) into single-molecule-wide chains and linear islands.