Engineers at the University of Ulster are the first researchers to create diamond nanorods with a diameter as thin as 2.1 nm, which is not only smaller than all the currently reported diamond 1D nanostructures (4-300 nm) but also smaller than the theoretical calculated value (2.7-9 nm) for energetically stable diamond nanorods. They actually established with the help of high resolution TEM studies carried both at Birmingham University and SuperSTEM facility in Daresbury Laboratory that the synthesis of ultrathin diamond nanorods (DNR) is possible, because they are encapsulated in a few graphene layers, which actually serve as a shield for keeping the DNR stable.
“This finding represents a milestone because it provides an insight on the growth of ultra-thin diamond nanorods and could actually act as a stimulus for future theoretical and experimental work” said Prof Papakonstantinou who is leader of the group at UU.
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.
The ultrathin nanords were fabricated in a microwave plasma assisted chemical vapor deposition reactor using a mixture gas of nitrogen and methane gases. Together with some diamond nanocluster, graphene nanowires and carbon nanotubes, diamond nanorods were self-assembled into a spherical electron-emitting structure. This integrated self assembled nanostructure demonstrated excellent field electron emission performance, better than that of all other conventional (Mo and Si tips, etc.) and popular nanostructural ?eld emitters.
“This novel DNR-based integrated nanostructure has a potential for use as low-power cold cathodes as well as for medical technological applications” said Dr Naigui Shang a researcher at UU