| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuE |
| Session: | Growth & Characterization of 2D Materials |
| Presenter: | Boris Feigelson, U.S. Naval Research Laboratory, USA |
| Authors: | B.N. Feigelson, U.S. Naval Research Laboratory, USA K. Sridhara, Texas A & M, USA J.K. Hite, U.S. Naval Research Laboratory, USA A. Nath, George Mason University J.A. Wollmershauser, U.S. Naval Research Laboratory, USA |
| Correspondent: | Click to Email |
The development of 2D hBN/graphene heterostructures is still in the early stages and largely depends on possibility to grow these heterostructures as well as on rapid and accurate characterization of the grown hBN/graphene layers. Along with graphene, atomically thin two dimensional hexagonal boron nitride (2D hBN) is one of the key materials in the development of new van der Waals heterostructures due to its outstanding properties including an atomically smooth surface, high thermal conductivity, high mechanical strength, chemical inertness and high electrical resistance.
In this work, hBN/graphene films were grown by atmospheric-pressure CVD on metal substrates (mainly Cu, but also Cu-Ni alloys). A vertical custom-made CVD reactor was used to grow 2D hBN/graphene films. The design of the vertical reactor allows the simultaneous growth of a few samples of hBN/graphene layers on different substrates in the same run.
As it was shown in our previous work [1], Fourier transform grazing-incidence infrared reflection absorption spectroscopy (FT-IRRAS) can be used to characterize monolayer and few-layer h-BN films directly on metal substrates. Two sub-bands of the A2u(LO) vibrational mode were found for thin 2D h-BN films in contact with Cu and Ni. The lower-energy A2u(LO)1 sub-band around 819 cm-1 is related to 2D h-BN coupled with Cu substrate, while the higher energy A2u(LO)2 sub-band around 824 cm-1 is related to decoupled (essentially free standing) 2D h-BN.
The IR-active out-of-plane vibrational mode was exploited to identify and characterize 2D hBN in grown heterostructures directly on metal substrates, while graphene was characterized by micro Raman spectroscopy. Combining FTIR and Raman spectroscopy allows express and in-depth characterization of hBN/graphene heterostructures directly on metal substrates used for growth.
The approach also provides an opportunity to determine which growth conditions lead to the absorption of foreign species on the substrate prior to the heterostructure deposition. Such interfacial layers were shown to result in easily-recognizable shifts in the A2u(LO) peak. The degree to which the interaction of the hBN layer with the substrate is uniform and homogenous can also be assessed easily by examining the width and fine structure of the A2u(LO) band.
B. N. Feigelson, V. M. Bermudez, J. K. Hite, Z. R. Robinson, V. D. Wheeler, K. Sridhara, and S. C. Hernandez, Nanoscale 7, 3694 (2015)