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Title: Quantitative analysis of chemical interaction and doping of the Si(111) native oxide surface with tetrafluorotetracyanoquinodimethane

The charge-transfer states and the carrier concentration of the native oxide Si(111) surface adsorbed with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F{sub 4}-TCNQ) were investigated by X-ray photoelectron spectroscopy (XPS) and independently driven four-probe electrical conductivity measurements. The XPS results show that F{sub 4}-TCNQ molecules are involved in charge transfer with the SiO{sub 2}/Si(111) surface. The Si 2p XPS spectra and the surface photovoltage shift provide the evidences of (i) change in the oxidation states at the SiO{sub 2}-Si(111) interface region and (ii) formation of a p-type space charge layer (SCL) with a hole concentration of 1.7 × 10{sup 10} cm{sup −2}, respectively. The four-probe I–V measurements also support the formation of the p-type SCL, and the estimated hole concentration of 2.0 × 10{sup 10} cm{sup −2} agrees well with the XPS results. The estimated SCL hole concentrations were much smaller than the excess charge density in the F{sub 4}-TCNQ layer, of the order of 10{sup 13} cm{sup −2}, suggesting that most of charges were localized as the oxidation states at the SiO{sub 2}-Si(111) interface region. The present quantitative methods ensure precise determination of the doping concentration near the surface region.
Authors:
; ; ; ; ; ; ;  [1]
  1. The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)
Publication Date:
OSTI Identifier:
22273595
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHARGE DENSITY; CONCENTRATION RATIO; CRYSTAL STRUCTURE; DEPLETION LAYER; ELECTRIC CONDUCTIVITY; ELECTRON SPECTRA; HETEROCYCLIC COMPOUNDS; HOLES; MOLECULES; NITRILES; SILICON; SILICON OXIDES; SURFACES; VALENCE; X-RAY PHOTOELECTRON SPECTROSCOPY