| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeE |
| Session: | Emerging Topics: Growth and Properties of Electronic Materials, 2D Layers, and Metallic-glass Thin Films |
| Presenter: | Boris Feigelson, Naval Research Laboratory |
| Authors: | B.N. Feigelson, Naval Research Laboratory K. Sridhara, US Naval Research Laboratory J.K. Hite, US Naval Research Laboratory J.A. Wollmershauser, 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. Growth of single and multi-layer (2-10 layers) h-BN films of high crystalline quality in controlled manner is still a challenge.
In this work, h-BN films were grown by atmospheric-pressure CVD on metal substrates (Cu, Ni and Cu-Ni alloys). A vertical custom-made CVD reactor was used to grow h-BN films. The design of the vertical reactor allows the simultaneous growth of a few samples of h-BN on different substrates in the same run. Ni-Cu and Cu-Ni alloys were prepared by electroplating Cu on to Ni and Ni on Cu foils, respectively, followed by thermal annealing and polishing [1] to create alloy substrates with increasing Cu or Ni concentrations (at 10 wt.% increments from 10-50 wt.% Cu in Ni and 10-50 wt.% Ni in Cu).
As it was shown in our previous work [2], 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) h-BN.
The IR-active out-of-plane vibrational mode was exploited to identify and characterize 1-5 layer h-BN on metal substrates, while micro Raman spectroscopy was used to characterize thicker h-BN films. Scanning electron microscope and x-ray photoelectron spectroscopy were used to probe the h-BN crystal size and stoichiometry.
Results on how morphology and thickness of 2D h-BN films depend on Cu-Ni alloy composition will be presented.
[1] K. Sridhara, B. N. Feigelson, J. A. Wollmershauser, J. K. Hite, A. Nath, S. C. Hernández, M. S. Fuhrer and D. K. Gaskill (2017). Crystal Growth & Design 17(4): 1669-1678.
[2] 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)