2026-09-25T09:50:21Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/125752 2026-02-03 col_2142_5131 col_2142_13836 com_2142_5130 com_2142_13835 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2026-08-01 The student, Hongye Sun, accepted the attached license on 2024-06-14 at 16:54. The student, Hongye Sun, submitted this Dissertation for approval on 2024-06-14 at 16:55. This Dissertation was approved for publication on 2024-06-24 at 16:09. DSpace SAF Submission Ingestion Package generated from Vireo submission #20837 on 2025-02-04 at 21:24:58 Scanning tunneling microscopy and spectroscopy of metallic features and nanocontacts for atomically precise graphene nanoribbons on silicon surface Sun, Hongye 2024-06-24 Lyding, Joseph W Lyding, Joseph W Abelson, John R Girolami, Gregory S Cao, Qing Zhang, Yingjie Graphene Nanoribbon Scanning Tunneling Microscopy Scanning Tunneling Spectroscopy Electron-beam-induced Deposition Hafnium Diboride Magnesium Boride Silicon Nanotechnology eng This thesis investigates the fabrication and electronic properties of metallic nanostructures and nanocontacts formed with atomically precise graphene nanoribbons (GNRs) on silicon surfaces. Scanning tunneling microscope (STM)-based electron beam induced deposition (EBID) was employed to write sub-5 nm metallic magnesium boride (MgBx) nanostructures directly onto hydrogen-passivated Si(100) surfaces. The effects of deposition parameters like voltage, current, writing speed, and repetition cycles on the dimensions and uniformity of the MgBx nanostructures were systematically investigated. Pre-fabricated niobium contact electrodes with narrow gaps were utilized to measure the conductivity of the MgBx nanowires and explore their potential superconducting behavior at cryogenic temperatures, though no superconductivity was observed. The STM-EBID technique using a hafnium precursor was further applied to form metallic nanocontacts directly onto individual solution-synthesized GNRs exfoliated on Si(100) surfaces. Scanning tunneling spectroscopy revealed induced p-n junction formation at the metal-GNR interface due to work function differences, creating a local band-bending effect useful for engineering the electronic properties. Moreover, strategies were developed to fabricate large-area metal electrode arrays on insulating silicon dioxide layers, enabling the precise writing of HfB2 interconnects to bridge individual GNRs with the electrodes for in-situ transport measurements. Finally, a simplified cleaning process combining high-temperature ultra-high vacuum annealing with piranha solution or UV ozone treatment was demonstrated for preserving atomically flat hydrogen-passivated Si(100) surfaces, facilitating GNR deposition and surface characterization after device fabrication steps. 2024-08 Thesis https://hdl.handle.net/2142/125752 Copyright 2024 Hongye Sun Materials Science & Engineerng Materials Science & Engr University of Illinois at Urbana-Champaign Ph.D. Dissertation