Graphene nanoribbons initiated from molecularly derived seeds

Semiconducting graphene nanoribbons are promising materials for nanoelectronics but are held back by synthesis challenges. Here we report that molecular-scale carbon seeds can be exploited to initiate the chemical vapor deposition (CVD) synthesis of graphene to generate one-dimensional graphene nanoribbons narrower than 5 nm when coupled with growth phenomena that selectively extend seeds along a single direction. This concept is demonstrated by subliming graphene-like polycyclic aromatic hydrocarbon molecules onto a Ge(001) catalyst surface and then anisotropically evolving size-controlled nanoribbons from the seeds along (110) of Ge(001) via CH4 CVD. Armchair nanoribbons with mean normalized standard deviation as small as 11% (3 times smaller than nanoribbons nucleated without seeds), aspect ratio as large as 30, and width as narrow as 2.6 nm (tunable via CH4 exposure time) are realized. Two populations of nanoribbons are compared in field-effect transistors (FETs), with off-current differing by 150 times because of the nanoribbons' different widths.

Automated summary

This study demonstrates a method to synthesize one-dimensional graphene nanoribbons narrower than 5 nm using molecular-scale carbon seeds and chemical vapor deposition (CVD). The nanoribbons are grown by selectively extending the seeds along a single direction. The synthesized nanoribbons have small standard deviation, large aspect ratio, and tunable width. Field-effect transistors based on the nanoribbons show a significant difference in off-current due to the variation in nanoribbon widths.