title: Adsorption of ammonia on graphene.
abstract: We report on experimental studies of NH3 adsorption/desorption on graphene surfaces. The study employs bottom-gated graphene field effect transistors supported on Si/SiO2 substrates. Detection of NH3 occurs through the shift of the source-drain resistance maximum ('Dirac peak') with the gate voltage. The observed shift of the Dirac peak toward negative gate voltages in response to NH3 exposure is consistent with a small charge transfer (f approximately 0.068 +/- 0.004 electrons per molecule at pristine sites) from NH3 to graphene. The desorption kinetics involves a very rapid loss of NH3 from the top surface and a much slower removal from the bottom surface at the interface with the SiO2 that we identify with a Fickian diffusion process.
authors.affiliation: Department of Physics, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Hugo E
authors.initials: HE
authors.lastname: Romero
authors.forename: Prasoon
authors.initials: P
authors.lastname: Joshi
authors.forename: Awnish K
authors.initials: AK
authors.lastname: Gupta
authors.forename: Humberto R
authors.initials: HR
authors.lastname: Gutierrez
authors.forename: Milton W
authors.initials: MW
authors.lastname: Cole
authors.forename: Srinivas A
authors.initials: SA
authors.lastname: Tadigadapa
authors.forename: Peter C
authors.initials: PC
authors.lastname: Eklund
mesh_terms: D000327:Adsorption; D000641:Ammonia / Q000032:analysis / Q000737:chemistry*; D003460:Crystallization / Q000379:methods; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006108:Graphite / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000295:instrumentation; D010316:Particle Size; D013499:Surface Properties; D014159:Transducers; D014173:Transistors, Electronic
chemical_list: D046911:Macromolecular Substances; D000641:Ammonia; D006108:Graphite