Oriented bottom-up growth of armchair graphene nanoribbons on germanium
Graphene nanoribbon arrays, methods of growing graphene nanoribbon arrays and electronic and photonic devices incorporating the graphene nanoribbon arrays are provided. The graphene nanoribbons in the arrays are formed using a scalable, bottom-up, chemical vapor deposition (CVD) technique in which the (001) facet of the germanium is used to orient the graphene nanoribbon crystals along the [110] directions of the germanium.
1. A graphene nanoribbon array comprising:
a germanium substrate having a (001) facet; and
a plurality of graphene nanoribbons on the (001) facet of the germanium substrate;
wherein the graphene nanoribbons have aspect ratios of at least 5 and the average aspect ratio of the graphene nanoribbons in the plurality of graphene nanoribbons is at least 20; and
further wherein the graphene nanoribbons have the armchair crystallographic direction of graphene running all the way along their long axes and an armchair configuration along their edges, and further wherein the long axes of the graphene nanoribbons are oriented along a [110] direction of the germanium.
2. The array of claim 1 , wherein the plurality of graphene nanoribbons comprises graphene nanoribbons having edges with an rms roughness of 1 nm or lower over edge lengths of at least 40 nm.
3. The array of claim 1 , wherein the plurality of graphene nanoribbons comprises graphene nanoribbons having edges with an rms roughness of 0.5 nm or lower over edge lengths of at least 40 nm.
4. The array of claim 1 , wherein the plurality of graphene nanoribbons comprises graphene nanoribbons having edges with an rms roughness of 0 nm over edge lengths of at least 10 nm.
5. The array of claim 1 , wherein the plurality of graphene nanoribbons comprises a first portion of graphene nanoribbons having their long axis oriented along a first [110] direction of the germanium and a second portion of graphene nanoribbons having their long axis oriented along a second [110] direction of the germanium.
6. The array of claim 1 , wherein the (001) facet of the germanium comprises a series of (001) faceted terraces separated by steps that are a multiple of two atomic layers in height along a single [110] direction, and the graphene nanoribbons are oriented along the terraces with the armchair crystallographic direction of the graphene and the long nanoribbon axes oriented along a single [110] direction of the germanium.
7. The array of claim 6 , wherein the plurality of graphene nanoribbons include graphene nanoribbons having widths of 5 nm or less.
8. The array of claim 1 , wherein the plurality of graphene nanoribbons include graphene nanoribbons having widths of no greater than about 10 nm and average lengths of at least 200 nm.