School of Physics Colloquium

Speaker: Walt A. de Heer (Georgia Tech)

Host: Colin Parker

Title: Breakthroughs in epitaxial graphene electronics: semiconducting graphene and the spectacular edge state.

Abstract: Graphene electronics was conceived at Georgia Tech 22 years ago when the first graphene, devices were produced using graphene grown on silicon carbide substrates (so called epigraphene) [1], and the worlds’ first graphene electronics patent was filed[2]. The GT team has made steady progress since. Several years ago we noted that narrow graphene ribbons exhibited resistances that are always close to 26 k Ohms, which corresponds to the resistance quantum h/e2 where h is Planck’s constant an e is the charge of the electron, that turned out to be caused by a unique state at the edge of the ribbon. We have recently shown that this edge state does not involve an electron or a hole, which are the usual carriers of currents in graphene, but the carrier appears to be a combination of the two to form a zero-energy mode [3]. Moreover, several of its properties resemble those of a Majorana fermion which was predicted in 1937. Very recently we have also discovered that the first graphene layer to grow on the silicon terminated silicon carbide crystal face, which has long been considered to an insulator, is in fact an excellent semiconductor when it is properly annealed. It is found to have a band gap of 0.6 eV and a room temperature mobility that exceeds 5000 cm2/Vs, which is greater than that of silicon and exceeds all other 2D semiconductors by a factor of 20 or more (Nature, in press). These two breakthrough discoveries put epigraphene on the path to become an important new 2D electronic material.

1. Berger, C., et al., Ultrathin Epitaxial Graphite:  2D Electron Gas Properties and a Route toward Graphene-based Nanoelectronics. The Journal of Physical Chemistry B, 2004. 108(52): p. 19912

2. de Heer, W.A., Berger,C, First,P.N, Patterned thin film graphite devices and method for making same. US patent US7015142B2 (Provisional filed Jun. 12, 2003).

3. Prudkovskiy, V.S., et al., An epitaxial graphene platform for zero-energy edge state nanoelectronics. Nature Communications, 2022. 13(1): p. 7814.

Bio: Walt A. de Heer is a Georgia Tech Regents’ Professor of Physics. His pioneering epitaxial graphene program, initiated in 2001, was inspired by his discovery of the room temperature ballistic transport properties of carbon nanotubes in 1998 and focuses on developing a viable silicon carbide platform for graphene-based nanoelectronics, which is currently his main interest. He has published more than 400 papers on epigraphene, carbon nanotubes and metallic clusters. He has an h-index of 97, and he has received the Web of Science Group’s Highly Cited Researcher Award yearly from 2010-2019.