title: Near-field photocurrent nanoscopy on bare and encapsulated graphene.
abstract: Optoelectronic devices utilizing graphene have demonstrated unique capabilities and performances beyond state-of-the-art technologies. However, requirements in terms of device quality and uniformity are demanding. A major roadblock towards high-performance devices are nanoscale variations of the graphene device properties, impacting their macroscopic behaviour. Here we present and apply non-invasive optoelectronic nanoscopy to measure the optical and electronic properties of graphene devices locally. This is achieved by combining scanning near-field infrared nanoscopy with electrical read-out, allowing infrared photocurrent mapping at length scales of tens of nanometres. Using this technique, we study the impact of edges and grain boundaries on the spatial carrier density profiles and local thermoelectric properties. Moreover, we show that the technique can readily be applied to encapsulated graphene devices. We observe charge build-up near the edges and demonstrate a solution to this issue.
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain.
authors.forename: Achim
authors.identifier: http://orcid.org/0000-0002-5024-4201
authors.initials: A
authors.lastname: Woessner
authors.affiliation: CIC nanoGUNE, 20018 Donostia-San Sebastian, Spain.|Institute of Physics, Chinese Academy of Science, Beijing 100190, China.
authors.forename: Pablo
authors.initials: P
authors.lastname: Alonso-González
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Lundeberg
authors.affiliation: Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: Yuanda
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, 08193 Barcelona, Spain.
authors.forename: Jose E
authors.initials: JE
authors.lastname: Barrios-Vargas
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Navickaite
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Ma
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain.
authors.forename: Davide
authors.initials: D
authors.lastname: Janner
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.identifier: http://orcid.org/0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, 08193 Barcelona, Spain.
authors.forename: Aron W
authors.initials: AW
authors.lastname: Cummings
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain.|ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain.
authors.forename: Valerio
authors.initials: V
authors.lastname: Pruneri
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, 08193 Barcelona, Spain.|ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain.
authors.forename: Stephan
authors.initials: S
authors.lastname: Roche
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Pablo
authors.initials: P
authors.lastname: Jarillo-Herrero
authors.affiliation: Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: James
authors.initials: J
authors.lastname: Hone
authors.affiliation: CIC nanoGUNE and UPV/EHU, 20018 Donostia-San Sebastian, Spain.|IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hillenbrand
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain.|ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain.
authors.forename: Frank H L
authors.initials: FH
authors.lastname: Koppens