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The control of metal-silicon carbide contacts using a silicon interlayer. / Wai Yee Lee

Swansea University Author: Wai Yee Lee

Abstract

The effect of Si interlayers within Ni-SiC contacts was studied using X- ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM). Firstly an atomically clean surface was successfully obtained by depositing a 40A layer of Si onto the SiC s...

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Published: 2004
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42768
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spelling 2018-08-02T16:24:30.4297981 v2 42768 2018-08-02 The control of metal-silicon carbide contacts using a silicon interlayer. 4507e645c43b255d3a9734b43da0f624 NULL Wai Yee Lee Wai Yee Lee true true 2018-08-02 The effect of Si interlayers within Ni-SiC contacts was studied using X- ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM). Firstly an atomically clean surface was successfully obtained by depositing a 40A layer of Si onto the SiC surface, followed by an immediate anneal at 1000&deg;C to re-evaporate the Si and remove surface contaminants. The interlayer was formed in ultra-high vacuum (UHV) conditions by depositing a known thickness of Si onto the clean SiC surface at room temperature. The metal contact was then produced by a sequential deposition of various Ni thicknesses onto the interlayer so that contact formation could be accurately monitored. These contacts were then annealed sequentially from 400&deg;C to 1200&deg;C. At each stage the process was characterised by XPS. Si interlayer thicknesses of 20A, 40A and 60A were tested. Results show that the consumption of Si atoms occurs, either from the Si interlayer or from the bulk SiC, with the evolution of Ni silicides and a Ni-Si-C ternary compound. In addition, chemical shifts associated with the formation of silicides and Fermi shifts (indicative of surface band bending) were also observed. When annealed at temperatures up to 1000&deg;C, rapid formation of silicides is observed in the Si spectra, whilst the C spectra consisted of only bulk C and a small amount of free C. Conversely, for the Ni-SiC interface without a Si interlayer, the C spectra consisted of large amount of free C and hydrocarbon. As a result of annealing the interlayer samples, chemical shifts were observed as well as downward band bending, indicative of barrier lowering and complimentary to the generation of an Ohmic contact at these elevated temperatures. At 1200&deg;C, all silicides had been re-evaporated leaving a carbon-rich surface, plus the formation of graphite on the surface. The electrical properties of the Ni-SiC contacts with and without Si interlayer were assessed using current-voltage (I/V) measurements. The contacts with a Si interlayer exhibit various behaviour from Schottky to Ohmic depending on the thickness of the Si interlayer. An Ohmic contact, which required no annealing was obtained when using a thick Si interlayer of 60A. However, Ni-Si-SiC Schottky contacts formed with 20A and 40A thick Si interlayers were shown to be able to operate, with Schottky barriers of ~1.7eV, up to 400&deg;C higher than the normal Ni-SiC contact, indicating the superior control of these interfaces when Si is used as an interlayer. E-Thesis Electrical engineering. 31 12 2004 2004-12-31 COLLEGE NANME Engineering COLLEGE CODE Swansea University Doctoral Ph.D 2018-08-02T16:24:30.4297981 2018-08-02T16:24:30.4297981 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Wai Yee Lee NULL 1 0042768-02082018162520.pdf 10807537.pdf 2018-08-02T16:25:20.4430000 Output 27226894 application/pdf E-Thesis true 2018-08-02T16:25:20.4430000 false
title The control of metal-silicon carbide contacts using a silicon interlayer.
spellingShingle The control of metal-silicon carbide contacts using a silicon interlayer.
Wai Yee Lee
title_short The control of metal-silicon carbide contacts using a silicon interlayer.
title_full The control of metal-silicon carbide contacts using a silicon interlayer.
title_fullStr The control of metal-silicon carbide contacts using a silicon interlayer.
title_full_unstemmed The control of metal-silicon carbide contacts using a silicon interlayer.
title_sort The control of metal-silicon carbide contacts using a silicon interlayer.
author_id_str_mv 4507e645c43b255d3a9734b43da0f624
author_id_fullname_str_mv 4507e645c43b255d3a9734b43da0f624_***_Wai Yee Lee
author Wai Yee Lee
author2 Wai Yee Lee
format E-Thesis
publishDate 2004
institution Swansea University
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
document_store_str 1
active_str 0
description The effect of Si interlayers within Ni-SiC contacts was studied using X- ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM). Firstly an atomically clean surface was successfully obtained by depositing a 40A layer of Si onto the SiC surface, followed by an immediate anneal at 1000&deg;C to re-evaporate the Si and remove surface contaminants. The interlayer was formed in ultra-high vacuum (UHV) conditions by depositing a known thickness of Si onto the clean SiC surface at room temperature. The metal contact was then produced by a sequential deposition of various Ni thicknesses onto the interlayer so that contact formation could be accurately monitored. These contacts were then annealed sequentially from 400&deg;C to 1200&deg;C. At each stage the process was characterised by XPS. Si interlayer thicknesses of 20A, 40A and 60A were tested. Results show that the consumption of Si atoms occurs, either from the Si interlayer or from the bulk SiC, with the evolution of Ni silicides and a Ni-Si-C ternary compound. In addition, chemical shifts associated with the formation of silicides and Fermi shifts (indicative of surface band bending) were also observed. When annealed at temperatures up to 1000&deg;C, rapid formation of silicides is observed in the Si spectra, whilst the C spectra consisted of only bulk C and a small amount of free C. Conversely, for the Ni-SiC interface without a Si interlayer, the C spectra consisted of large amount of free C and hydrocarbon. As a result of annealing the interlayer samples, chemical shifts were observed as well as downward band bending, indicative of barrier lowering and complimentary to the generation of an Ohmic contact at these elevated temperatures. At 1200&deg;C, all silicides had been re-evaporated leaving a carbon-rich surface, plus the formation of graphite on the surface. The electrical properties of the Ni-SiC contacts with and without Si interlayer were assessed using current-voltage (I/V) measurements. The contacts with a Si interlayer exhibit various behaviour from Schottky to Ohmic depending on the thickness of the Si interlayer. An Ohmic contact, which required no annealing was obtained when using a thick Si interlayer of 60A. However, Ni-Si-SiC Schottky contacts formed with 20A and 40A thick Si interlayers were shown to be able to operate, with Schottky barriers of ~1.7eV, up to 400&deg;C higher than the normal Ni-SiC contact, indicating the superior control of these interfaces when Si is used as an interlayer.
published_date 2004-12-31T03:53:36Z
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score 11.013686

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