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Overview of Characterization Methodology Michael J. Kelley College of William & Mary and Jefferson Lab [email protected] PowerPoint PPT Presentation


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Overview of Characterization Methodology Michael J. Kelley College of William & Mary and Jefferson Lab [email protected] A View of Characterization Science The materials equivalent of analytical chemistry Product, Microstructure Processing Characterization Service

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Overview of Characterization Methodology Michael J. Kelley College of William & Mary and Jefferson Lab [email protected]

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Overview of Characterization Methodology

Michael J. Kelley

College of William & Mary and Jefferson Lab

[email protected]


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A View of Characterization Science

The materials equivalent of analytical chemistry

Product,

Microstructure

Processing Characterization Service

Environment

StartingUnderstanding, Performance

Materials Improvement End-use


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What are We Looking At ?

Counts (au)

Counts (au)

Nb 3d

Nb 3d

Binding Energy (eV)

Binding Energy (eV)

The surface chemistry of niobium is dominated by high reactivity toward oxygen. The outermost layers are always found to be Nb2O5, suboxides NbO2, NbO and Nb2O are also known and, in various combinations and morphologies, are proposed to be between the Nb2O5 and the underlying metal [4-7] .

The surface chemistry of niobium is dominated by high reactivity toward oxygen. The outermost layers are always found to be Nb2O5, suboxides NbO2, NbO and Nb2O are also known and, in various combinations and morphologies, are proposed to be between the Nb2O5 and the underlying metal [4-7] .

Hydrocarbons & impurities

Nb hydroxides

Nb2O5, dielectric

NbOx (0.2 < x < 2),metallic

NbOx precipitates (0.02 < x < 0.2)

(Penetration depth : ~ 40 nm)

Hydrocarbons & impurities

Nb hydroxides

Nb2O5, dielectric

NbOx (0.2 < x < 2),metallic

NbOx precipitates (0.02 < x < 0.2)

(Penetration depth : ~ 40 nm)

Crystallites:

size, orientation, contaminants

Topography:

average roughness, variability,

sharpest features

Chemistry:

Nb speciation, contaminants

Near-surface:

Oxide layers, adjacent metal

Effect of process changes

Variability within cavity

Can we use coupons ?

Effect of post-treatment ?

Statistics and sampling ?

BCP

EP


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Surface Morphology

Polycrystal Nb

Single crystal Nb

200 nm/div

EP treated polycrystal Nb surfaces are significantly smoother than that of BCP treated,

The ridges at the grain boundaries are smaller than BCP treated surfaces;

BCP treated single crystal Nb surface is comparable to EP treated polycrystal Nb

BCP

200 nm/div

EP

Optical microscopy images

AFM images for BCP treated SC & EP treated PC

Typical performance: vertical – few nm to several tenths mm; horizontal – 30 nm


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Structure: Diffraction in the SEMEBSD – Electron Backscatter Diffraction

Crystalline materials diffract the primary electrons

Backscatter is slightly reduced along major planes - pattern of dark lines

Automated systems are now available to index channeling patterns

Useful for orientation images of flat surfaces

Samples about 50 nm depth.


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Pole

Figures

EBSD by Matt Nowell at

EDAX/TSL

1.5 x 1.5 mm field after BCP. Stereographic triangle indicates grain orientation

Black dots appear to be pits. Are they associated with grain boundaries ?

EBSD is available as a standard SEM accessory – nothing but money !


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Nb2O5

NbOx

Nb

Surface

concept

Hydrocarbons & impurities

Nb hydroxides

Dielectric Nb2O5

NbOx (0.2 < x < 2),metallic

NbOx precipitates (0.02 < x < 0.2)

Nb (Penetration depth : ~ 40 nm)

Is it layers ?

What are species ?

Effect of topography

Effect of treatment

X-ray Photoelectron

Spectroscopy: XPS

Energy conservation:

hn = K.E. + B.E.

Nb species can be resolved

Lateral resolution: < 10 mm

Data acquisition and analysis

can be automated


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Varying photon energy to

vary sampling depth in XPS

hn = K.E. + B.E.

B.E. of Nb 3d 5/2 = 202.2 eV

Inelastic Mean Free Path, nm

  • hn depth

  • 300 1.76

  • 550 3.31

  • 930 5.34

  • 1254 7.01

Mg

Al

X 1 B

[Photoelectron Kinetic]

M.P.Seah, W.A.Dench; Surf.Int.Analy.1(1979) 1


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TEM Operating Modes

Bright field - pass central beam only. scatterers are dark

Dark field - select and pass diffracted beam only. Only the Diffracting species is bright

High resolution - pass two beams under phase-contrast (interference) conditions

STEM - convergent (spot) beam - operate like SEM


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TEM Contrast Mechanisms-3

Phase contrast -

Electrons travelling different paths experience different phase shifts

A plane wave entering becomes phase modulated with structure information

Characteristic distances are ~ 10 nm

Combining beams creates interference image.


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Phase Contrast Development

Note: beam direction is a zone axis


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Au-Pd

Oxide

~7.0 nm

Nb

Would show fringes

if crystalline

Dale Batchelor, North Carolina State University


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Secondary Ion Mass Spectroscopy (SIMS)Concepts

  • Bombard with (0.5) 5 keV - 25 keV ions

  • Ions penetrate the surface, displacing atoms which in turn displace others: Collision Cascade

  • A few collision trains reach the surface

  • “Entities” are ejected with near-thermal energy

    [0.5 mm vs 50 nm lateral resolution]


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Ion Collision Cascade Concepts

Effect of topography, recoil implantation


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D-SIMS

shallow

implant

profile

Quantification requires standards


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Sputter Profile

Issues

The ion beam unavoidably

drives some of struck atoms

deeper into the solid than

their original position (knock

-on mixing), distorting the

depth profile. A sputter

profile from the backside -

possible only with special

samples - reveals the size of

the effect. Spectra of B in Si.

K.L.Yeo et al.; J.Vac.Sci.Technol.

B21 (2003) 193


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Summary

SEM – EBSD is effective for grain size and orientation.

AFM – Effective for topography, but scatter and rare events are issues. Need lots of data.

XPS – Effective for Nb speciation and oxide thickness estimation. Improved lateral resolution helps

HRTEM – Cross-sections are promising, but extensive study is needed. $$ !!

SIMS – Sensitive, but depth profiling issues about topography and mixing. Need standards.


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“Our Best Facilities”

XPS: PHI/Ulvac “Quanterra”, NSLS X1B

SEM: Hitachi 4700 with EDS, EBSD

FIB: FEI “Helios” dual beam with SEM and EBSD

TEM: FEI “Titan”; JEOL 2100-F; Hitachi HF-2000

Dynamic SIMS: Cameca 6f, 7f

Static SIMS: PHI “Trift-II”

AES: PHI 660 SAM

“Shared courses”


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