Interactions of Organic Radicals and Transition Metals with the Surfaces of Group-IV Elements

Abstract

Covalent Functionalization of Epitaxial Graphene by Azidotrimethylsilane Chemically modified epitaxial graphene (EG) by azidotrimethylsilane (ATS) was investigated using highresolution photoemission spectroscopy (HRPES). Through the spectral analysis, we clearly confirmed that EG is modified by thermally generated nitrene radicals and found that the bonding nature between the nitrene radicals and EG is covalent. As we observe bonding nature of N 1s peaks, we found that two distinct N peaks can be clearly distinguished in the spectra. Using a covalently bound stretched graphene (CSG) model, we elucidated that nitrene radicals adsorb on the graphene layer at two different adsorption sites. Moreover, we were able to control the band gap of EG using valence band spectra as we change the amount of the dosing of nitrene.

Chemical Doping of Epitaxial Graphene by Organic Free Radicals Chemical doping of epitaxial graphene (EG) by organic free radicals (4-amino-2,2,6,6-tetramethyl-1-piperridinyloxy; 4-amino-TEMPO) was investigated using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and high resolution photoemission spectroscopy (HRPES). STM images revealed that the empty density of states near the adsorption site significantly decreased as a result of radical doping. STS indicated that 4-amino-TEMPO radicals acted as n-type dopants on both monolayer and bilayer graphene. The radicals adsorbed onto EG through the nitroxide groups, leaving the amine group unreacted, which was confirmed by the binding energies of N 1s and O 1s core-level spectra. Furthermore, the measured work function changes verified that increased adsorption of the radicals on EG showed n-type doping characteristics.

Adsorption Structures of Co on Si(100) The adsorption of Co on Si(100) at room temperature was studied using scanning tunneling microscope (STM). The Co atoms penetrate into the subsurface interstitial site beneath the Si dimer. The incorporation of Co atom l...