Self-Assembled Growth, Microstructure, and Field-Emission High-Performance of Ultrathin Diamond Nanorods

TLDR

The study reports growing ultrathin diamond nanorods via microwave plasma CVD with nitrogen/methane and proposes them as low‑power cold cathodes. The DNRs are synthesized by microwave plasma CVD, encapsulated in tapered CNTs with a (111)diamond//(0002)graphite orientation, and formed via a heterogeneous self‑catalytic vapor‑solid process. The ultrathin DNRs, with a 2.1 nm diameter, self‑assemble into isolated electron‑emitting spherules that achieve a low‑threshold field emission of 10 mA cm⁻² at 2.9 V µm, outperforming conventional emitters except oriented CNTs.

Abstract

We report the growth of ultrathin diamond nanorods (DNRs) by a microwave plasma assisted chemical vapor deposition method using a mixture gas of nitrogen and methane. DNRs have a diameter as thin as 2.1 nm, which is not only smaller than reported one-dimensional diamond nanostructures (4−300 nm) but also smaller than the theoretical value for energetically stable DNRs. The ultrathin DNR is encapsulated in tapered carbon nanotubes (CNTs) with an orientation relation of (111)diamond//(0002)graphite. Together with diamond nanoclusters and multilayer graphene nanowires/nano-onions, DNRs are self-assembled into isolated electron-emitting spherules and exhibit a low-threshold, high current-density (flat panel display threshold: 10 mA/cm2 at 2.9 V/μm) field emission performance, better than that of all other conventional (Mo and Si tips, etc.) and popular nanostructural (ZnO nanostructure and nanodiamond, etc.) field emitters except for oriented CNTs. The forming mechanism of DNRs is suggested based on a heterogeneous self-catalytic vapor−solid process. This novel DNRs-based integrated nanostructure has not only a theoretical significance but also has a potential for use as low-power cold cathodes.