title: Chemical surface passivation of Ge nanowires.
abstract: Surface oxidation and chemical passivation of single-crystal Ge nanowires with diameters ranging between 7 and 25 nm were studied. The surface chemistry differs significantly from that of well-studied monolithic atomically smooth single-crystal substrates. High-resolution Ge 3d XPS measurements reveal that Ge nanowires with chemically untreated surfaces exhibit greater susceptibility to oxidation than monolithic Ge substrates. Multiple solution-phase routes to Ge nanowire surface passivation were studied, including sulfidation, hydride and chloride termination, and organic monolayer passivation. Etching in HCl results in chloride-terminated surfaces, whereas HF etching leads to hydride termination with limited stability. Exposure to aqueous ammonium sulfide solutions leads to a thick glassy germanium sulfide layer. Thermally initiated hydrogermylation reactions with alkenes produce chemically stable, covalently bonded organic monolayer coatings that enable ohmic electrical contacts to be made to the nanowires.
authors.affiliation: Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, Austin, TX 78712-1062, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hanrath
authors.forename: Brian A
authors.initials: BA
authors.lastname: Korgel