| AVS 62nd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Monday Sessions |
| Session 2D+EM+NS+PS+SP+SS+TF-MoM |
| Session: | 2D Materials: Growth and Fabrication |
| Presenter: | Boris Feigelson, US Naval Research Laboratory |
| Authors: | B.N. Feigelson, US Naval Research Laboratory V.M. Bermudez, US Naval Research Laboratory J.K. Hite, US Naval Research Laboratory Z.R. Robinson, US Naval Research Laboratory V.D. Wheeler, US Naval Research Laboratory K. Sridhara, US Naval Research Laboratory S.C. Hernández, US Naval Research Laboratory |
| Correspondent: | Click to Email |
Atomically thin two dimensional hexagonal boron nitride (2D h-BN) 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. The development of 2D h-BN growth is still in the early stages and largely depends on rapid and accurate characterization of the grown monolayer or few layers h-BN films.
In this work, the IR-active out-of-plane vibrational mode of 2D h‑BN films grown in vertical reactor by atmospheric-pressure CVD on metal substrates (mainly Cu but also Ni) is exploited to identify 2D h‑BN directly on substrates and studied both computationally and experimentally.
Fourier transform grazing-incidence infrared reflection absorption spectroscopy (FT-IRRAS) data have been used to characterize monolayer and few-layer h-BN films directly on metal substrates. Two sub-bands of the A2u(LO) vibrational mode were, for the first time, found for thin 2D h-BN films in contact with Cu and Ni [1]. To unveil the nature of the discovered sub-bands, ab-initio calculations were performed and verified using 2D h-BN films grown on various Cu substrates with varying coverage and with individual crystallites of different shapes and size up to 4 mm. It was shown that 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. These findings demonstrate not only a new and facile method for immediate 2D h-BN identification and characterization, but also a method that provides a simple means to characterize the degree of coupling between 2D h-BN and the substrate. This approach also provides an opportunity to determine which growth conditions lead to the absorption of foreign species on the substrate prior to the h-BN deposition and which conditions can prevent the formation of the interfacial layer between h-BN and the substrate. Such interfacial layers, like oxidized Cu, were shown to result in easily-recognizable shifts in the A2u(LO) peak. The degree to which the interaction of the h BN 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. The developed approach can also be used to study growth and formation of h-BN/graphene and other 2D heterostructures.
References
1. 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)