Graphene-Nanotube Junctions: Switches without Semiconductors

On July 20, 2015, the Scientific Reports published a paper titled “Switching Behaviors of Graphene-Boron Nitride Nanotube Heterojunctions” about two materials combined to make a digital switch that could improve high speed computing. We have asked one of the authors of this research, Prof. Yoke Khin Yap, to comment on this work.

The Study

Downsizing digital switches using silicon transistors are facing a series of fundamental limitation including the inherent heating issue and low switching ratios. Instead of attempting to resolve these semiconductor physics, we made a bore step toward making switches without using semiconductors. This will by-pass the current limitation of downsizing semiconducting transistors and digital switches.

Background

Physicists find new type of robust electron channels Inspired by the structure of graphene, scientists design a new class of topological insulators with possible applications in quantum technologies

In 2013, we published our original work in Advanced Materials on making transistors without using semiconductor. Specifically, we put a one-dimensional array of gold quantum dots on the electrically insulating boron nitride nanotubes (BNNTs).

The physical gaps between QDs stop electron flows (“off” state) but allow electron tunneling when sufficient electric field is applied (“on” state). In the recent work published in Scientific Reports, we “fused” the semimetallic graphene with BNNTs to make digital switches. These graphene-BNNT heterojuctions represent a new form of digital switches without using semiconductor with a switching ratio 100’s thousand time.

Future Direction

There are two major advantages of graphene-BNNT switches. The first one is the use of graphene, which could offer very high electron mobility. The second one is the lattice matching between the carbon and boron nitride materials, which allow the formation of seamless junctions that would eliminate electron scattering.

The use of graphene alone can not form digital switches as graphene is a conductor, with no mean to stop current flow. the graphene-BNNT junctions create a stopping valve and allow electron to tunnel across only when sufficient electric field is applied. The next step for the field is to create seamless carbon-boron nitride junctions in a rational manner.