title: Microwave near-field imaging of two-dimensional semiconductors.
abstract: Optimizing new generations of two-dimensional devices based on van der Waals materials will require techniques capable of measuring variations in electronic properties in situ and with nanometer spatial resolution. We perform scanning microwave microscopy (SMM) imaging of single layers of MoS2 and n- and p-doped WSe2. By controlling the sample charge carrier concentration through the applied tip bias, we are able to reversibly control and optimize the SMM contrast to image variations in electronic structure and the localized effects of surface contaminants. By further performing tip bias-dependent point spectroscopy together with finite element simulations, we distinguish the effects of the quantum capacitance and determine the local dominant charge carrier species and dopant concentration. These results underscore the capability of SMM for the study of 2D materials to image, identify, and study electronic defects.
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
authors.forename: Samuel
authors.initials: S
authors.lastname: Berweger
authors.forename: Joel C
authors.initials: JC
authors.lastname: Weber
authors.forename: Jimmy
authors.initials: J
authors.lastname: John
authors.forename: Jesus M
authors.initials: JM
authors.lastname: Velazquez
authors.forename: Adam
authors.initials: A
authors.lastname: Pieterick
authors.forename: Norman A
authors.initials: NA
authors.lastname: Sanford
authors.forename: Albert V
authors.initials: AV
authors.lastname: Davydov
authors.forename: Bruce
authors.initials: B
authors.lastname: Brunschwig
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Lewis
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Wallis
authors.forename: Pavel
authors.initials: P
authors.lastname: Kabos
keywords: MoS2; Transition metal dichalcogenide; atomic force microscope; microwave; near-field; quantum capacitance