title: Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals.
abstract: A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current-voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium-graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT) calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of theI-Vcharacteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed.
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
authors.forename: Ivan
authors.initials: I
authors.lastname: Shtepliuk
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Eriksson
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Khranovskyy
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
authors.forename: Tihomir
authors.initials: T
authors.lastname: Iakimov
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
authors.forename: Anita
authors.initials: A
authors.lastname: Lloyd Spetz
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
authors.forename: Rositsa
authors.initials: R
authors.lastname: Yakimova
keywords: Schottky diode; SiC; barrier height; graphene; heavy metals; sensing platform