Despite certain desirable electrical characteristics of single- and multi-layer graphene, the development of circuits such as field-effect transistors (FETs) based on this semi-metal has often been impractical. For instance, such materials often do not exhibit a bandgap as is desirable in the operation of various circuits.
One type of graphene material that has been developed is graphitic nanomaterial, sometimes in the form of graphitic nanoribbon material, having small widths. Such nanoribbons may be made via the lateral unzipping of carbon nanotubes, or plasma etching of graphene through nanoscale masks that may, for example, be prepared using nanospheres, block copolymers or lithography. In these methods, a chemical reaction occurs at an edge and results in the formation of the graphene nanoribbon structure. However, for such materials less than 10 nm in width, disorder at the edges can significantly impact electronic properties.
Direct synthesis of such graphitic materials has also been achieved. One such approach involves using bottom-up synthesis from molecular components, in which a surface-catalyzed chemical reaction is used to form nanoscale ribbons of desired shapes based on the molecular precursors. Another approach is based on epitaxial graphene growth on silicon carbide utilizing the preferential precipitation of graphene on pre-patterned facets. This latter method relies on lithography to define the molecular terraces that serve as a support for graphitic nanoribbon growth, meaning the width of the resulting graphene nanoribbon structures is limited by lithography (e.g., in the range of 15 to 40 nm).
These and other matters have presented challenges to semiconductor apparatuses and related methods, for a variety of applications.