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Quasi-Free-Standing Single Layer of Graphene and Hexagonal Boron Nitride on Pt(111) by a Single Molecular Precursor

A novel bottom-up approach to obtain a continuous almost free-standing hexagonal single layer with perfectly merging graphene and hexagonal boron-nitride domains using only one molecular precursor. S. Nappini et al. Adv. Funct. Mat. (2015). 10.1002/adfm.201503591 and S. Nappini et al Carbon (2017) doi:10.1016/j.carbon.2017.05.026

 

 


Research in graphene (G)-based photonics and electronics is currently facing the challenge of adapting the electronic properties of this material to a wide range of applications. Here we report a novel bottom-up approach to obtain a continuous almost free-standing hexagonal single layer with merging G and hexagonal boron-nitride (h-BN) domains using only onemolecular precursor. This straightforward growth method is easily adaptable to industrial processes aiming at engineering the band gap of G by merging in the same layer the isostructural h-BN, characterized by very different carrier mobility due to its wide bandgap. Up to now, however, G-h-BN layers have been obtained only by complex routes, starting from two or three precursors or growing h-BN on existing G patches and vice-versa.
We have demonstrated that a simple thermal decomposition of dimethylamine borane is sufficient to obtain a G-h-BN layer on Pt(111).This growth route allows an easy and controlled preparation of a continuous almost freestanding layer mostly composed by G and h-BN in the same two dimensional sheet by dehydrogenation and pyrolytic decomposition of DMAB on Pt(111). The temperature is the principal parameter to selectively grow the G-h-BN layer in competition with hybridized B-C-N layers on the clean crystal surface.
We have grown and investigated the h-BNG layer on Pt(111) at the BACH beamline by high-resolution core level X-ray photoemission (XPS) and near-edge absorption spectroscopy (NEXAFS) and at the Nanospectroscopy beamline by low energy electron microscopy (LEEM) combined with X-ray photoemission electron microscopy (XPEEM), micro-spot electron energy loss spectroscopy (µ-EELS) and low energy electron diffraction (µ-LEED) data.

We have obtained the in-plane G-h-BN layer in UHV by dosing 150 L of commercial dimethylamine borane molecules on a (111)-terminated platinum single crystal held at elevated temperatures. 1000 K was found to be the optimal substrate temperature to get the most ordered and flat surface.

Evidence of in-plane G-h-BN layer continuity has been established by Temperature Programmed Desorption Spectroscopy and weak interaction with Pt substrate has been ascertained by high-resolution Pt4f7/2 core level spectroscopy, which shows bulk and surface components identical to those of the clean Pt(111).


 

The local atomic order of the in-plane G-h-BN layer grown on Pt(111) was investigated by LEEM and µ-LEED, complemented by XPEEM and µ-EELS. The presence of a heterostructure is revealed by LEEM micrographs in bright field (BF)  where a clear image contrast between darker and brighter complementary areas is ascribable to the presence of two phases on the sample.


Our findings demonstrate that dehydrogenation and pyrolytic decomposition of DMAB is an efficient and easy method for obtaining a continuous almost freestanding layer made of G, h-BN in the same two dimensional sheet on a metal substrate, such as Pt(111), paving the way for the advancement of next-generation G-like-based electronics and novel spintronic devices.
 

Besides the formation of quasi–free–standing continuous monolayer formed by complementary hexagonal boron nitride and graphene (G), we have also demonstarted that the selective formation of different in-plane boron–nitrogen–carbon heterostructures can be achieved using the same precursor. Through thermally activated decomposition and sequential bond activation it is possible to control intermolecular coupling and obtain alternatively a  pure or doped G monolayer, or hybridized layers with non-planar bonds. The selective bond–bond coupling is achieved by controlling the substrate temperature either during or after the deposition of DMAB. This allows on-surface synthesis of B–N–C materials with tunable composition.

 

Formation of a Quasi-Free-Standing Single Layer of Graphene and Hexagonal Boron Nitride on Pt(111) by a Single Molecular Precursor
Silvia Nappini, Igor Píš, Tefvik Onur Menteş, Alessandro Sala, Mattia Cattelan, Stefano Agnoli, Federica Bondino*, Elena Magnano*
Advanced Functional Materials (2015) . DOI: 10.1002/adfm.201503591
*bondino@iom.cnr.it, magnano@iom.cnr.it

On-surface synthesis of different boron–nitrogen–carbon heterostructures from dimethylamine borane 
Nappini S., Píš I., Carraro G., Celasco E., Smerieri M., Savio L., Magnano E., Bondino F. Carbon (2017) doi: 10.1016/j.carbon.2017.05.026

Free download until July 26th from this link:
http://www.sciencedirect.com/science/article/pii/S0008622317304724

 


This work was supported by the Italian MIUR through the national grant Futuro in ricerca 2012 RBFR128BEC ‘‘Beyond graphene: tailored C-layers for novel catalytic materials and green chemistry’’

 

 

Last Updated on Wednesday, 12 December 2018 12:56