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Effect of Nitrogen on the Stability ...

Zhao, Yue,

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Effect of Nitrogen on the Stability and Thermomechanical Behavior of the β Phase in Tungsten Thin Films /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Effect of Nitrogen on the Stability and Thermomechanical Behavior of the β Phase in Tungsten Thin Films // Yue Zhao.
Author:	Zhao, Yue,
Description:	1 electronic resource (240 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
Contained By:	Dissertations Abstracts International86-12B.
Subject:	Materials science. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31996862
ISBN:	9798283140391

Effect of Nitrogen on the Stability and Thermomechanical Behavior of the β Phase in Tungsten Thin Films /
Zhao, Yue,

Effect of Nitrogen on the Stability and Thermomechanical Behavior of the β Phase in Tungsten Thin Films /Yue Zhao. - 1 electronic resource (240 pages)

Source: Dissertations Abstracts International, Volume: 86-12, Section: B.

While tungsten is well known for having a single equilibrium crystal structure, the body-centered cubic (BCC) α phase, a metastable β phase with the A15 structure has been extensively observed in tungsten thin films. Tungsten thin films containing the β phase exhibit unique properties, such as high-temperature superconductivity and the giant spin Hall effect (GSHE), making them promising for applications in advanced electronics. However, the study and utilization of this phase has been hindered by: (1) Unclear and inconsistent deposition protocols for reliably fabricating 100% β. (2) Limited understanding in its thermal stability, including the specific conditions and atomistic mechanisms for its irreversible transformation to the stable α phase upon heating. (3) Huge stress variations with temperature that can lead to failure during device processing. (4) A general lack of knowledge on many of its fundamental material properties.To address these challenges, we have: (1) Demonstrated that high-quality β-W films with known phase and elemental compositions can be reliably and reproducibly fabricated by introducing nitrogen during sputter deposition, and established the quantitative relationship between nitrogen content and β phase volume fraction in as-deposited films. (2) Shown that increasing nitrogen content enhances the thermal stability of β-W, developed an analytical model describing the β-α phase transition in the presence of nitrogen, extracted relevant activation energies, and explained the atomistic mechanism responsible for nitrogen stabilization. (3) Systematically characterized film stress in β-W as a function of temperature and nitrogen content using high-resolution in-situ substrate curvature measurements, and linked the observed thermomechanical behavior to underlying microstructural and compositional changes. (4) Used thermoelastic stress-temperature data from substrate curvature measurements to accurately determine the coefficient of thermal expansion (CTE) and biaxial modulus of β-W as functions of nitrogen content, with errors below 3%, and further verified these results through molecular dynamics (MD) and ab-initio molecular dynamics (AIMD) simulations.

English

ISBN: 9798283140391Subjects--Topical Terms:

543314
Materials science.
Subjects--Index Terms:

Metastable phase

Effect of Nitrogen on the Stability and Thermomechanical Behavior of the β Phase in Tungsten Thin Films /
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520 $a While tungsten is well known for having a single equilibrium crystal structure, the body-centered cubic (BCC) α phase, a metastable β phase with the A15 structure has been extensively observed in tungsten thin films. Tungsten thin films containing the β phase exhibit unique properties, such as high-temperature superconductivity and the giant spin Hall effect (GSHE), making them promising for applications in advanced electronics. However, the study and utilization of this phase has been hindered by: (1) Unclear and inconsistent deposition protocols for reliably fabricating 100% β. (2) Limited understanding in its thermal stability, including the specific conditions and atomistic mechanisms for its irreversible transformation to the stable α phase upon heating. (3) Huge stress variations with temperature that can lead to failure during device processing. (4) A general lack of knowledge on many of its fundamental material properties.To address these challenges, we have: (1) Demonstrated that high-quality β-W films with known phase and elemental compositions can be reliably and reproducibly fabricated by introducing nitrogen during sputter deposition, and established the quantitative relationship between nitrogen content and β phase volume fraction in as-deposited films. (2) Shown that increasing nitrogen content enhances the thermal stability of β-W, developed an analytical model describing the β-α phase transition in the presence of nitrogen, extracted relevant activation energies, and explained the atomistic mechanism responsible for nitrogen stabilization. (3) Systematically characterized film stress in β-W as a function of temperature and nitrogen content using high-resolution in-situ substrate curvature measurements, and linked the observed thermomechanical behavior to underlying microstructural and compositional changes. (4) Used thermoelastic stress-temperature data from substrate curvature measurements to accurately determine the coefficient of thermal expansion (CTE) and biaxial modulus of β-W as functions of nitrogen content, with errors below 3%, and further verified these results through molecular dynamics (MD) and ab-initio molecular dynamics (AIMD) simulations.
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650 4 $a Engineering. $3 586835
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653 $a Thermal stability
653 $a Thermomechanical behavior
653 $a Thin films
653 $a Tungsten
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