| AVS 65th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Tuesday Sessions |
| Session NS+AM+MI+MN+SS+TR-TuA |
| Session: | SPM – Probing and Manipulating Nanoscale Structures |
| Presenter: | Chuanxu Ma, Oak Ridge National Laboratory |
| Authors: | C. Ma, Oak Ridge National Laboratory L. Liang, Oak Ridge National Laboratory Z. Xiao, North Carolina State University A.A. Puretzky, Oak Ridge National Laboratory K. Hong, Oak Ridge National Laboratory W. Lu, North Carolina State University J. Bernholc, North Carolina State University A.-P. Li, Oak Ridge National Laboratory |
| Correspondent: | Click to Email |
High quality electrical contact to low-dimensional semiconductor channel materials is the key to unlocking their unique electronic and optoelectronic properties for fundamental research and device applications. Inappropriate contacts create interfacial states that can pin the Fermi level and form a large Schottky barrier. For 2D transition metal dichalcogenides (TMDs), a route to a high-performance contact has recently been proposed by using a phase transition that converts a hexagonally packed semiconductor (2H) phase into a distorted octahedrally packed metallic (1T’) phase. However, a similar approach is not available for 1D materials. Conceptually, an ideal contact would be a metal-semiconductor interface formed with native covalent bonds without introduction of any structural or electronic boundaries. Realization of such a seamless contact in 1D materials such as graphene nanoribbons (GNRs) requires atomically precise development of a heterostructure from well-defined atomic or molecular precursors.
Here we report on a successful approach for making seamless contacts in 1D materials through the formation of GNR staircase heterostructure. The coherent staircase is made of GNRs with widths varying from 7, 14, 21 and up to 56 carbon atoms. The graphitic heterostructures are synthesized by a surface-assisted self-assembly process with a single molecular precursor. While the 7-atom-wide GNR is a large-gap semiconductor, the conjugated wide GNRs are either quasi-metallic or small-gap semiconductors, similarly to the 2D metals. Our study, which combines STM and Raman measurements with DFT calculations, reveals that the heterointerface consists of native sp2 carbon bonds without localized interfacial states. Such a seamless heterostructure offers an optimal electrical contact to the wide-gap 1D semiconductor.