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Title: Interfacial band alignment and structural properties of nanoscale TiO{sub 2} thin films for integration with epitaxial crystallographic oriented germanium

We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO{sub 2}) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO{sub 2} thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO{sub 2} thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO{sub 2}/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 ± 0.02 eV was determined for the amorphous TiO{sub 2} thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO{sub 2}/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO{sub 2}/Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ΔE{sub V}(100) > ΔE{sub V}(111) > ΔE{sub V}(110) and a conduction band-offset relation of ΔE{sub C}(110) > ΔE{sub C}(111) > ΔE{sub C}(100).more » These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO{sub 2} for potential high-κ dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.« less
Authors:
; ;  [1] ; ; ;  [2]
  1. Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)
  2. Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)
Publication Date:
OSTI Identifier:
22271257
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 2; 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; 77 NANOSCIENCE AND NANOTECHNOLOGY; CRYSTAL STRUCTURE; DIELECTRIC MATERIALS; ELECTRONIC STRUCTURE; ELLIPSOMETRY; FIELD EFFECT TRANSISTORS; GALLIUM ARSENIDES; GERMANIUM; LAYERS; MOLECULAR BEAM EPITAXY; NANOSTRUCTURES; ORIENTATION; PHYSICAL VAPOR DEPOSITION; SEMICONDUCTOR MATERIALS; SUBSTRATES; THIN FILMS; TITANIUM OXIDES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY PHOTOELECTRON SPECTROSCOPY