Hexagonal Boron Nitride Single Crystal Thermal Oxidation and Etching in Air: An Atomic Force Microscopy Study
- PDF / 1,074,451 Bytes
- 8 Pages / 432 x 648 pts Page_size
- 70 Downloads / 200 Views
MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.667
Hexagonal Boron Nitride Single Crystal Thermal Oxidation and Etching in Air: An Atomic Force Microscopy Study N. Khan1, E. Nour1, J. Mondoux1, S. Liu2, J.H. Edgar2, and Y. Berta3 1
Georgia Gwinnett College, School of Science and Technology, Lawrenceville, GA, 30043
2
Kansas State University, Tim Taylor Department of Chemical Engineering, Manhattan, KS, 66506
3
Georgia Institute of Technology, School of Material Science and Engineering, Atlanta, GA 30332
ABSTRACT
Hexagonal boron nitride (hBN), a two dimensional (2D) material, has emerged as an important substrate and dielectric for electronic, optoelectronic, and photonic devices based on graphene and other atomically thin two dimensional materials. Here we report on the initial oxidation of (0001) hBN single crystals in ambient air as functions of temperature and time, as determined by atomic force microscopy (AFM) and scanning electron microscope with energy dispersive X-ray spectroscopy (SEM/EDS). For oxidation times of 20 minutes, the first evidence of oxidation appears at 900°C, with the formation of shallow, hexagonal-, and irregular-shaped pits that are less than 100 nm across and several nanometer deep. Oxidation at 1100°C for 20 minutes produced 1.0-2.0-micron size pits with flat and pointed bottoms that were approximately hexagonal-shaped, but with rough and irregular edges, and multiple interior steps. Oxidation was not uniform on the surface of hBN, but starts where dislocations in the crystal intersected the surfaces. Pit depth increased linearly with temperature and oxidation times. In addition to the surface pits, small particles formed on the surface. Elemental analysis of the thermally oxidized hBN crystals by SEM/EDS revealed the major elements of these particles were boron and oxygen.
Downloaded from https://www.cambridge.org/core. Iowa State University Library, on 14 Jan 2019 at 05:50:29, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2018.667
INTRODUCTION Hexagonal boron nitride (h-BN), a two dimensional (2D) material with a wide indirect band gap (~6 eV) [1], possesses excellent physical properties, and high thermal and chemical stability [2-4]. Moreover, it has a small lattice mismatch ~ 1.7% with graphene [3,5]. These exceptional properties make it suitable as an encapsulation material, tunneling barrier, top-based thermal interface material, and 2D dielectric substrates for graphene based electronics [3-7]. Furthermore, hBN substrates provides graphene with a smooth supporting surface that reduces local microscopic charge inhomogeneity, and thus produces a higher charge mobility as compared to graphene on silicon dioxide (SiO2) substrates [8-10]. hBN is frequently employed as a protective coating of graphene, because it does not oxidize until high temperatures. While the oxidation of graphene in air begin within 5 minutes at 500 °C [11], several studies on hBN oxidation reported
Data Loading...
