doi:10.1038/nindia.2017.58 Published online 26 May 2017
The performance of future electronic devices using nanotechnologies is set to improve thanks to a new and better process for synthesizing Hexagonal Boron Nitride (h-BN), an ultra-thin insulator used with wonder-nanomaterial graphene1.
Graphene is only one or two atoms thick, while also being very strong, and a heat and electricity conductor. It shows promise in creating everything from paper-thin television screens to bullet proof vests, but needs an insulating layer so that it can be held while electrically charged.
The compound h-BN is the world’s thinnest insulator and it has an atomically smooth surface devoid of charged impurities. This surface makes it an ideal material to support a layer of graphene, which requires an impurity-free and ultra-smooth interface.
Several techniques have been employed to synthesize thin films of h-BN, but most create structural defects that in turn degrade graphene performance. Now Sanjay Behura and Vikas Berry at the University of Illinois in Chicago report a new improved process for producing the h-BN insulating layer.
Currently, a h-BN film is produced on top of a metallic layer (like copper, nickel, cobalt or iron) and then transferred onto silicon-based layers. "These transfer steps consistently degrade h-BN’s structure via formation of tears, folds, wrinkles, and adsorption of polymeric or metallic impurities," Behura and Berry told Nature India.
The researchers and their colleagues at technology company SunEdison Semiconductor have leveraged surface chemical interactions of h-BN precursors to form large-area, thin films of h-BN directly onto silicon-based layers, eliminating the defect-creating first step.
They also created large-area ‘heterostructures’, or layered structures, of h-BN with graphene via an all ‘chemical-vapor-deposition’ approach. The researchers found this exhibited 3.5-fold enhancement in charge carrier mobility – the speed at which a charge like electricity moves through the material in a given direction – compared to graphene on silicon-based gate dielectric field effect transistor devices.
The application of these methods could help produce future technologies ranging from nanoscale electronics to energy conversion devices and optoelectronics, the researchers say.
1. Behura, S. et al. Chemical interaction-guided, metal-free growth of large-area hexagonal boron nitride on silicon-based substrates. ACS Nano 11, 4985–4994 (2017) doi: 10.1021/acsnano.7b01666