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Title: Atomic-layer deposited thulium oxide as a passivation layer on germanium

A comprehensive study of atomic-layer deposited thulium oxide (Tm{sub 2}O{sub 3}) on germanium has been conducted using x-ray photoelectron spectroscopy (XPS), vacuum ultra-violet variable angle spectroscopic ellipsometry, high-resolution transmission electron microscopy (HRTEM), and electron energy-loss spectroscopy. The valence band offset is found to be 3.05 ± 0.2 eV for Tm{sub 2}O{sub 3}/p-Ge from the Tm 4d centroid and Ge 3p{sub 3/2} charge-corrected XPS core-level spectra taken at different sputtering times of a single bulk thulium oxide sample. A negligible downward band bending of ∼0.12 eV is observed during progressive differential charging of Tm 4d peaks. The optical band gap is estimated from the absorption edge and found to be 5.77 eV with an apparent Urbach tail signifying band gap tailing at ∼5.3 eV. The latter has been correlated to HRTEM and electron diffraction results corroborating the polycrystalline nature of the Tm{sub 2}O{sub 3} films. The Tm{sub 2}O{sub 3}/Ge interface is found to be rather atomically abrupt with sub-nanometer thickness. In addition, the band line-up of reference GeO{sub 2}/n-Ge stacks obtained by thermal oxidation has been discussed and derived. The observed low reactivity of thulium oxide on germanium as well as the high effective barriers for holes (∼3 eV) and electrons (∼2 eV) identify Tm{sub 2}O{sub 3} as amore » strong contender for interfacial layer engineering in future generations of scaled high-κ gate stacks on Ge.« less
Authors:
; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4] ; ; ; ;  [5] ; ;  [6]
  1. Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ (United Kingdom)
  2. Department of Physics and Stephenson Institute for Renewable Energy, University of Liverpool, Liverpool L69 7ZF (United Kingdom)
  3. ENEA, Frascati Research Centre, via E. Fermi 45, 00044 Frascati (Italy)
  4. Department of Engineering, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom)
  5. School of ICT, KTH Royal Institute of Technology, Isafjordsgatan 22, 164 40 Kista (Sweden)
  6. CEMES-CNRS and Université de Toulouse, nMat group, BP 94347, 31055 Toulouse Cedex 4 (France)
Publication Date:
OSTI Identifier:
22412872
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 21; Other Information: (c) 2015 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; DEPOSITION; ELECTRON DIFFRACTION; ELECTRONS; ELLIPSOMETRY; ENERGY-LOSS SPECTROSCOPY; EV RANGE; FILMS; GERMANIUM; GERMANIUM OXIDES; HOLES; INTERFACES; LAYERS; OXIDATION; PASSIVATION; POLYCRYSTALS; THULIUM OXIDES; TRANSMISSION ELECTRON MICROSCOPY; VALENCE; X-RAY PHOTOELECTRON SPECTROSCOPY