Emre Ertuğrul

20824006

Emin Şahin

20824259

Seçkin Gökçe

20824044

KMU 396

Material Science and Technology

Outline of Lecture

Introduction

-advantages,

-disadvantages

Principles of ESCA

The photoelectron effect

Instrumentation

Analysis Capabilities

-Elemental analysis

-Chemical state analysis

-More complex effects

Surface Sensitivity

•Introduction -History of AES -General Uses •Principles of Operation •Instrumentation •Auger Spectrum •Common Applications •Advantages & Disadvantages of AES

ESCA AES

Introduction ESCA provides unique information about chemical composition

And chemical state of a surface

useful for biomaterials

advantages -- surface sensitive (top few monolayers) -- wide range of solids -- relatively non-destructive disadvantages -- expensive, slow, poor spatial resolution, requires high vacuum

Principles of ESCA

ESCA is based on the photoelectron effect.

A high energy X-ray photon can ionize an atom

Detecting electrons ejected from higher orbitals

producing an ejected free electron with kinetic energy KE:

KE=hv-BE

*BE=energy necessary to remove a specific electron from an atom. BE ≈ orbital energy *h=Planck Constant *v=frequency of light

Instrumentation Essential components: Sample: usually 1 cm2 X-ray source: Al: 1486.6 eV;

Mg 1256.6 eV Electron Energy Analyzer:

100 mm radius concentric hemispherical analyzer; vary voltages to vary pass energy.

Detector: electron multiplier (channeltron)

Electronics, Computer Note: All in ultrahigh

vacuum (<10-8 Torr) (<10-11 atm)

State-of-the-art small spot ESCA: 10 mm spot size.

Figure A

http://www.sphysics.com/

AES in Laboratory

Analysis Capabilities

Elemental Analysis: atoms have valence and

core electrons: Core-level Binding energies

provide unique signature of elements.

Quantitative analysis: measure intensities,

use standards or sensitivity factor

Applications

-- Surface contamination

-- Failure analysis

-- Effects of surface treatments

-- Coating, films

-- Tribological effects

-- Depth Profiling (Ar+ sputtering)

ESCA studies of polyimide Pyromellitic dianhydride -- oxydianiline

PMDA - ODA

Figure B

Introduction to Auger Electron Spectroscopy (AES) Auger Electron Spectroscopy (AES), is a widely used

technique to investigate the composition of surfaces.

First discovered in 1923 by Lise Meitner and later independently discovered once again in 1925 by Pierre Auger [1]

Lise Meitner Pierre Victor Auger

1. P. Auger, J. Phys. Radium, 6, 205 (1925).

General Uses Surface composition analysis for metals, powders,

insulators,

Identification of particulates, localized dopants or contaminants, visual defects

Investigation of submicrometer dimension structures

Grain boundary investigations, e.g. intergranular corrosion

Analysis of surface coatings and thin films

When combined with ion sputtering, elemental depth profiling of surface and/or interfacial layers

Principles of Operation

Auger Electron Spectroscopy Ions Electrons Photons

Vacuum

Ions Electrons Photons

• sample bombardment by electrons •core electron removed • electron from a higher energy level fall into the vacancy •release of energy. •measured energy and defined sample

AES Instrument Configuration

Elements of Typical Auger System: Electron Gun Analyzer Secondary Electron Detector Ion Gun Sample Stage Introduction System

Auger Spectrum

Figure C

http://mee-inc.com/sam.html

Advantages

• Monolayer-sensitive surface analysis with high

spatial resolution

•Elemental mapping across surface

•Elemental depth profiling with uniform sensitivity

• It is sensitive to light elements (except H and He).

Limits of Technique and Disadvantages

•Surface Sensitivity: < 1 nm

•Lateral Resolution: < 50 nm

•Analytical Volume: 10-18 cm3

•Insulators are difficult to study due to surface

charging.

•Surface may be damaged by the incident electron

beam.

Summary

ESCA & AES is very important

analytical techniques used in

materials science to investigate

molecular surface structures and

their electronic properties.

References

•http://www.rci.rutgers.edu/.../LECTURE5

•http://nanoall.blogspot.com/2011/10/auger-electron-

spectrometry-aes.html

•http://www.orlabs.com/AugerElectronSpectroscopy.php

•http://www.wellesley.edu/Chemistry/Chris/AES.html

•http://www.Ism.rutgers.edu/esca/principles.html

•http://www.jhu.edu/chem/fairbr/surfacelab/aes.html

Thank You All …