Ultrathin Chemical Vapor Deposition (CVD)-Grown Hexagonal Boron Nitride as a High-Quality Dielectric for Tunneling Devices on Rigid and Flexible Substrates

Abstract

We investigate the tunneling properties of large-area monolayer hexagonal boron nitride (BN) grown via chemical vapor deposition (CVD) by fabricating metal/BN/metal devices on rigid and flexible substrates and compare the properties to metal/exfoliated BN/graphite devices. The measured current of the tunneling devices sandwiched by metal electrodes is linear around zero bias and increases exponentially at higher biases, a behavior consistent with direct tunneling. We also investigate the effect of PMMA contamination on the tunneling current by comparing the zero-bias resistances of the BN devices that have undergone PMMA cleaning by acetone and by heat treatment. Annealing under Ar/O2 at 500 °C proves to be the best heat treatment for removing the PMMA contaminants introduced during BN transfer, though extra care must be given because this condition can also roughen the bottom electrodes. Further, from tunneling theory, we estimate the barrier height for tunneling to be ∼2.5 eV, and the dielectric strength to be 3.78 ± 0.83 GV m–1, which are comparable to those of exfoliated monolayer BN. Our results demonstrate that CVD-grown BN can be a perfect alternative to exfoliated BN for tunneling applications, such as vertical transistors and spintronics, with an advantage of being available in a large area.