title: Dopant Diffusion and Activation in Silicon Nanowires Fabricated by ex Situ Doping: A Correlative Study via Atom-Probe Tomography and Scanning Tunneling Spectroscopy.
abstract: Dopants play a critical role in modulating the electric properties of semiconducting materials, ranging from bulk to nanoscale semiconductors, nanowires, and quantum dots. The application of traditional doping methods developed for bulk materials involves additional considerations for nanoscale semiconductors because of the influence of surfaces and stochastic fluctuations, which may become significant at the nanometer-scale level. Monolayer doping is an ex situ doping method that permits the post growth doping of nanowires. Herein, using atom-probe tomography (APT) with subnanometer spatial resolution and atomic-ppm detection limit, we study the distributions of boron and phosphorus in ex situ doped silicon nanowires with accurate control. A highly phosphorus doped outer region and a uniformly boron doped interior are observed, which are not predicted by criteria based on bulk silicon. These phenomena are explained by fast interfacial diffusion of phosphorus and enhanced bulk diffusion of boron, respectively. The APT results are compared with scanning tunneling spectroscopy data, which yields information concerning the electrically active dopants. Overall, comparing the information obtained by the two methods permits us to evaluate the diffusivities of each different dopant type at the nanowire oxide, interface, and core regions. The combined data sets permit us to evaluate the electrical activation and compensation of the dopants in different regions of the nanowires and understand the details that lead to the sharp p-i-n junctions formed across the nanowire for the ex situ doping process.
authors.affiliation: Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208-3108, United States.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel.
authors.forename: Ori
authors.initials: O
authors.lastname: Hazut
authors.affiliation: Institute of Physics, Academia Sinica , Nankang, Taipei 115, Taiwan.
authors.forename: Bo-Chao
authors.initials: BC
authors.lastname: Huang
authors.affiliation: Institute of Physics, Academia Sinica , Nankang, Taipei 115, Taiwan.|Department of Physics, National Taiwan Normal University , Taipei 116, Taiwan.
authors.forename: Ya-Ping
authors.initials: YP
authors.lastname: Chiu
authors.affiliation: Institute of Physics, Academia Sinica , Nankang, Taipei 115, Taiwan.
authors.forename: Chia-Seng
authors.initials: CS
authors.lastname: Chang
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel.
authors.forename: Roie
authors.initials: R
authors.lastname: Yerushalmi
authors.affiliation: Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208-3108, United States.
authors.forename: Lincoln J
authors.initials: LJ
authors.lastname: Lauhon
authors.affiliation: Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208-3108, United States.|Northwestern University Center for Atom-Probe Tomography (NUCAPT) , 2220 Campus Drive, Evanston, Illinois 60208-3108, United States.
authors.forename: David N
authors.initials: DN
authors.lastname: Seidman
keywords: Silicon nanowire; atom-probe tomography; diffusion; ex situ doping; monolayer doping