Molybdenum disulphide (MoS2) is a promising material for heterogeneous catalysis and novel 2D optoelectronic devices. In this work, single-layer MoS2 is synthesized on Au(111) by pulsed laser deposition, showing the potentialities of this technique in the synthesis of high-quality 2D materials films.
The interaction between molybdenum disulfide monolayers and gold is studied by combining scanning tunneling microscopy (STM) measurements on extended MoS 2 films grown by pulsed laser deposition and density functional theory (DFT) calculations. The lattice mismatch between MoS 2 and Au leads to the growth of extended monolayer films displaying a noncommensurate lattice with the metal substrate. STM images are also characterized by a high concentration of features related to two kinds of point defects. DFT calculations highlight the role of the local MoS 2 /Au registry in driving the film−substrate interaction, showing that in the regions of the moirésuperlattice where a top coincidence is found, Au atoms are lifted up to some extent as a result of the interaction with the MoS 2 film, reducing remarkably the interfacial distance. The combination of ab initio thermodynamics and Tersoff−Hamann simulated images permits us to assign the most commonly observed defect features to single-sulfur vacancies located either on the outer surface or at the interface with gold. This fact has important implications on the conductivity and catalytic properties of this material.
The structure and electronic and vibrational properties of sp–sp2 carbon atomic wires have been investigated by combined STM/STS and Raman spectroscopy.
Graphdiyne, atomically thin two-dimensional
(2D) carbon nanostructure
based on sp-sp
2
hybridization is an appealing system potentially
showing outstanding mechanical and optoelectronic properties. Surface-catalyzed
coupling of halogenated sp-carbon-based molecular precursors represents
a promising bottom-up strategy to fabricate extended 2D carbon systems
with engineered structure on metallic substrates. Here, we investigate
the atomic-scale structure and electronic and vibrational properties
of an extended graphdiyne-like sp-sp
2
carbon nanonetwork
grown on Au(111) by means of the on-surface synthesis. The formation
of such a 2D nanonetwork at its different stages as a function of
the annealing temperature after the deposition is monitored by scanning
tunneling microscopy (STM), Raman spectroscopy, and combined with
density functional theory (DFT) calculations. High-resolution STM
imaging and the high sensitivity of Raman spectroscopy to the bond
nature provide a unique strategy to unravel the atomic-scale properties
of sp-sp
2
carbon nanostructures. We show that hybridization
between the 2D carbon nanonetwork and the underlying substrate states
strongly affects its electronic and vibrational properties, modifying
substantially the density of states and the Raman spectrum compared
to the free standing system. This opens the way to the modulation
of the electronic properties with significant prospects in future
applications as active nanomaterials for catalysis, photoconversion,
and carbon-based nanoelectronics.
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