Robust All-Carbon Molecular Junctions on Flexible or Semi-Transparent Substrates Using Process-Friendly Fabrication

Large area molecular junctions were fabricated on electron-beam deposited carbon (eC) surfaces with molecular layers in the range of 2-5.5 nm between conducting, amorphous carbon contacts. Incorporating eC as an interconnect between Au and the molecular layer improves substrate roughness, prevents electromigration and uses well-known electrochemistry to form a covalent C-C bond to the molecular layer. Au/eC/anthraquinone/eC/Au junctions were fabricated on Si/SiOx with high yield and reproducibility and were unchanged by 107 current voltage cycles and temperatures between 80 and 450 K. Au/eC/AQ/eC/Au devices fabricated on plastic films were unchanged by 107 current density vs bias voltage (J-V) cycles and repeated bending of the entire assembled junction. The low sheet resistance of Au/eC substrates permitted junctions with sufficiently transparent electrodes to conduct Raman or UV vis absorption spectroscopy in either reflection or transmission geometries. Lithographic patterning of Au/eC substrates permitted wafer-scale integration yielding 500 devices on 20 chips on a 100 mm diameter wafer. Collectively, eC on Au provides a platform for fabrication and operation of chemically stable, optically and electrically functional molecules on rigid or flexible materials. The relative ease of processing and the robustness of molecular junctions incorporating eC layers should help address the challenge of economic fabrication of practical, flexible molecular junctions for a potentially wide range of applications.