Br/N-based dopants open up the band-gap in graphene nanoplatelets for the design of FETs

December 20, 2013 // By Julien Happich
Reaserchers at the Ulsan National Institute of Science and Technology (UNIST in Korea) unveiled a method for the mass production of boron/nitrogen co-doped graphene nanoplatelets, which led to the fabrication of a graphene-based field-effect transistor (FET).

Led by Prof. Jong-Beom Baek, the research team uses a simple solvothermal reaction of BBr3/CCl4/N2 in the presence of potassium to mass produce boron/nitrogen co-doped graphene nanoplatelets (BCN-graphene).

Since graphene was experimentally discovered in 2004, various methods of making graphene-based field effect transistors (FETs) have been exploited, including doping graphene tailoring graphene-like a nanoribbon, and using boron nitride as a support. Among the methods of controlling the band-gap of graphene, doping methods show the most promise in terms of industrial scale feasibility.

Although world leading researchers have tried to add boron into graphitic framework to open its band-gap for semiconductor applications, there has not been any notable success yet. Since the atomic size of boron (85 pm) is larger than that of carbon (77 pm), it is difficult to accommodate boron into the graphitic network structure.

The new synthetic protocol has revealed that boron/nitrogen co-doping is only feasible when carbon tetrachloride (CCl4) is treated with boron tribromide (BBr3) and nitrogen (N2) gas.

In order to help boron-doping into graphene structure, the research team used nitrogen (70 pm), which is a bit smaller than carbon and boron. The idea was very simple, but the result was surprising. Pairing two nitrogen atoms and two boron atoms can compensate for the atomic size mismatch. Thus, boron and nitrogen pairs can be easily introduced into the graphitic network. The resultant BCN-graphene generates a band-gap for FETs.

A schematic representation for the formation of BCN-graphene via solvothermal reaction between carbon tetrachloride (CCl4) boron tribromide (BBr3) and nitrogen (N2) in the presence of potassium (K).

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