X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy for chemical analysis (ESCA) is used to investigate the chemistry at the surface of the samples. The basic mechanism behind an XPS instrument is that the photons of a specific energy are used to excite the electronic states of atoms at and just below the surface of the sample.
There are several areas suited to measurement by XPS:
1. Elemental composition
2. Empirical formula determination
3. Chemical state
4. Electronic state
5. Binding energy
6. Layer thickness in the upper portion of surfaces
XPS has many advantages, such as it is is good for identifying all but two elements, identifying the chemical state on surfaces, and is good with quantitative analysis. XPS is capable of detecting the difference in the chemical state between samples. XPS is also able to differentiate between oxidations states of molecules.
XPS has also some limitations, for instance, samples for XPS must be compatible with the ultra high vacuum environment. XPS is limited to measurements of elements having atomic numbers of 3 or greater, making it unable to detect hydrogen or helium. XPS spectra also take a long time to obtain. The use of a monochromator can also reduce the time per experiment.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
Optical band gap measurement by diffuse reflectance spectroscopy (drs)Sajjad Ullah
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by electronic spectroscopy and diffuse reflectance spectroscopy (DRS) with comparison of the results obtained suing different equation and measurement techniques.
The role of scattering in extinction of light as it passes through media is briefly discussed.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
Optical band gap measurement by diffuse reflectance spectroscopy (drs)Sajjad Ullah
Introduction to Optical band gap measurement
by electronic spectroscopy and diffuse reflectance spectroscopy (DRS) with comparison of the results obtained suing different equation and measurement techniques.
The role of scattering in extinction of light as it passes through media is briefly discussed.
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NQR - DEFINITION - ELECTRIC FIELD GRADIENT - NUCLEAR QUADRUPOLE MOMENT - NUCLEAR QUADRUPOLE COUPLING CONSTANT - PRINCIPLE OF NQR - ENERGY OF INTERACTION - SELECTION RULE - FREQUENCY OF TRANSITION - APPLICATIONS
There are tables with the KE and BE already assigned to each
element.
• The plot has characteristic peaks for each element found in the
surface of the sample.
• The intensity of the peaks is related to the concentration.
• The technique provides a quantitative analysis of the surface
composition
Chemical state identification on surfaces
• Identification of all elements except for H and He
• Quantitative analysis, including chemical state differences between
samples
• Oxide thickness measurements
• Very simple to use and the data is easily analyzed.
• The UHV environment prevents contamination of the surface and
aid an accurate analysis of the sample.
• The XPS technique is non-destructive because it produces soft xrays to induce photoelectron emission from the sample surface
Instrumentation presentation - Auger Electron Spectroscopy (AES)Amirah Basir
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Normaizatul Hanissa Binti Hamdan
Amirah Binti Basir
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Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
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Collaborators and co editors: Charlie Sims and Connor Healey.
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When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
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TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSE
X ray Photoelectron Spectroscopy (XPS)
1. X-Ray Photoelectron Spectroscopy (XPS)
Presented By :Presented By :
Mr. Sanjeet Kumar Paswan
Research Scholar
Department of Nanoscience & Technology
Central University of Jharkhand , Ranchi-835205
2. OUTLINE
XPS Background
The Photoelectric process
X-Rays
XPS Instrument
How Does XPS Technology Work ?
Analysıs of XPS
The Atom and the X-Ray The Atom and the X-Ray
X-Rays on the Surface
Interpreting XPS Spectrum: Background
Identification of XPS Peaks
Advantages and Disadvantages
XPS Technology
References
3. X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy
for chemical analysis (ESCA) is a surface sensitive spectroscopic
technique widely used in materials science to investigate the
molecular surface stress , chemical composition of surfaces and their
electronic properties.
XPS technique is based on Einstein’s idea about the photoelectric
effect, developed around 1905.
The concept of photons was used to describe the ejection of
XPS Background
The concept of photons was used to describe the ejection of
electrons from a surface when photons were impinged upon it.
In 1960, Dr. Siegbahn and his research group, developed the XPS
technique and produce the first commercial monochromatic XPS and
in 1981, Dr. Seighbahn won the noble prize.
ESCA is based on the Photoelectron effect.
Electros knock away from the surface with definite hν shown in next slide
Fig.
4. Conduction BandConduction Band
Valence BandValence Band
FermiFermi
LevelLevel
FreeFree
ElectronElectron
LevelLevel
Incident XIncident X--rayray
Ejected PhotoelectronEjected Photoelectron
The Photoelectric process
L2,L3L2,L3
L1L1
KK1s1s
2s2s
2p2p
Following this process, the atom willFollowing this process, the atom will
release energy by the emission of anrelease energy by the emission of an
Auger Electron.Auger Electron.
Fig: Photoelectric effect
K.E = Ephoton – Ebinding + φ
Incoming X-ray and if it has some
energy and it ll observed by an atom
then initial electron ll ejected this
phenomena is known as Photoelectric
effect. Because energy of the X-ray
with the particular λ is known ejected
Photoelectron has K.E be calculated.
Φ is Work function
5. Conduction BandConduction Band
Valence BandValence Band
FermiFermi
LevelLevel
FreeFree
ElectronElectron
LevelLevel
Emitted Auger ElectronEmitted Auger Electron
Auger Relation of Core Hole
Sample bombardment by electrons and
core electrons removed.
Electron from a higher energy level fall
into the vacancy and after that release of
energy.
Measured energy and defined samples.
L electron falls to fill core level vacancy
L2,L3L2,L3
L1L1
KK1s1s
2s2s
2p2p
L electron falls to fill core level vacancy
(step1).
KLL Auger electron emitted to conserve
energy released in step1.
6. Binding Energy (BE)
The Binding Energy (BE) is characteristic of the core electrons for each element.
0
x
p+
B.E.
This is the point with 0 energy of
attraction between the electron and
the nucleus. At this point the
electron is free from the atom.
These electrons are attracted to the
proton with certain binding energy xp+ proton with certain binding energy x
B.E=Ehv-K.E-Ø
K.E is Kinetic Energy (measure in the XPS spectrometer).
hv is photon energy from the X-Ray source (controlled).
Ø is spectrometer work function. It is a few eV, it gets more complicated because
the materials in the instrument will affect it. Found by calibration.
B.E is the unknown variable.
The equation will calculate the energy needed to get an e- out from the surface of
the solid and Knowing KE, hv and Ø the BE can be calculated.
7. X-Rays
Irradiate the sample surface, hitting the core electrons (e-) of the atoms.
The X-Rays penetrate the sample to a depth on the order of a micrometer.
Useful e- signal is obtained only from a depth of around 10 to 100 Å on the
surface.
The X-Ray source produces photons with certain energies:
MgK photon with an energy of 1253.6 eV
AlK photon with an energy of 1486.6 eV
Normally, the sample will be radiated with photons of a single energy (MgK
or AlK). This is known as a monoenergetic X-Ray beam.or AlK). This is known as a monoenergetic X-Ray beam.
Why the Core Electrons ?
An electron near the Fermi level is far from the nucleus, moving in different
directions all over the place, and will not carry information about any single atom.
The core e-s are local close to the nucleus and have binding energies characteristic
of their particular element.
The core e-s have a higher probability of matching the energies of AlK and MgK.
Core e-
Valence e-
Atom
8. XPS Instrument
X-Ray Source
Ion Source
SIMS Analyzer
Sample introduction
Chamber
COMPONENTS OF XPS
A source of X-rays
An ultra high vacuum (UHV)
An electron energy analyzer
magnetic field shielding
An electron detector system
A set of stage manipulators
Essential Components
Sample : Usually 1 cm2
X-ray Source : Al is 1486.6 eV and Mg is 1256.6 eV.
Electron Energy Analyzer
Detector : Electron multiplier.
Electronics, Computer.
9. X-ray Photoelectron Spectrometer
ElectronElectron
OpticsOptics
Hemispherical Energy AnalyzerHemispherical Energy Analyzer
Magnetic ShieldShieldOuter SphereOuter Sphere
Inner SphereInner Sphere
ComputerComputer
SystemSystem
Analyzer ControlAnalyzer Control
MultiMulti--Channel PlateChannel Plate
Electron MultiplierElectron Multiplier
Lenses for EnergyLenses for Energy
AdjustmentAdjustment
5 4 . 7
XX--rayray
SourceSource
OpticsOptics
Position SensitivePosition Sensitive
Detector (PSD)Detector (PSD)
SampleSample
Electron MultiplierElectron Multiplier
Resistive AnodeResistive Anode
EncoderEncoder
AdjustmentAdjustment
(Retardation)(Retardation)
Lenses for AnalysisLenses for Analysis
Area DefinitionArea Definition
Position ComputerPosition Computer
Position AddressPosition Address
ConverterConverter
10. How Does XPS Technology Work ?
A monoenergetic x-ray beam
emits photoelectrons from the
surface of the sample.
The x-ray photons The
penetration about a micrometer of
the sample
The XPS spectrum contains
information only about the top 10
- 100 Ǻ of the sample.
Ultrahigh vacuum environment to
eliminate excessive surface
contamination.
Cylindrical Mirror Analyzer
(CMA) measures the KE of
emitted e-s.
The spectrum plotted by the
computer from the analyzer signal.
The binding energies can be
determined from the peak
positions and the elements presentpositions and the elements present
in the sample identified.
Which materials are analazıed?
XPS is routinely used to analyze inorganic compounds, metals, semiconductors,
polymers, ceramics,etc.
Organic chemicals are not routinely analyzed by XPS because they are readily
degraded by either the energy of the X-rays or the heat from non-monochromatic X-ray
sources.
11. ANALYSIS OF XPS
XPS detects all elements with (Z) >3. It cannot detect H (Z = 1) or He (Z = 2) because the
diameter of these orbitals is so small, reducing the catch probability to almost zero.
Dedection unit: ppt and some conditions ppm.
The Atom and the X-Ray
Valence electrons
X-Ray
Free electron
Core electrons
Valence electrons
proton
neutron
electron
electron vacancy
The core electrons respond
very well to the X-Ray
energy
12. X-Rays on the Surface
e- top layer
e- lower layer
with collisions
e- lower layer
but no collisions
X-Rays
Outer surface
Inner surface
Atoms layers
The surface contains the atom and molecules on the exterior of an object that can
interact with energy, atom and molecules outside of that objects.
13. The X-Rays will penetrate to the core e- of the atoms in the sample.
Some e-s are going to be released without any problem giving the Kinetic
Energies (KE) characteristic of their elements.
Other e-s will come from inner layers and collide with other e-s of upper
layers
These e- will be lower in lower energy.
They will contribute to the noise signal of the spectrum.
X-Rays on the Surface
14. KE versus BE
KE can be plotted depending on
BE
Each peak represents the amount
of e-s at a certain energy that is
characteristic of some element.
#ofelectrons
E E E
1000 eV 0 eV
BE increase from right to left
KE increase from left to right
Binding energy
(eV)
15. Interpreting XPS Spectrum: Background
• The X-Ray will hit the e-s in the bulk
(inner e- layers) of the sample
• e- will collide with other e- from top
layers, decreasing its energy to
contribute to the noise, at lower kinetic
energy than the peak .
• The background noise increases with
BE because the SUM of all noise is
taken from the beginning of the
analysis.
#ofelectrons
N2
N3
N4
N = noise
Binding energy
#ofelectrons
N1
N2
Ntot= N1 + N2 + N3 + N4
• The XPS peaks are sharp.
• In a XPS graph it is possible to see Auger electron peaks.
• The Auger peaks are usually wider peaks in a XPS spectrum.
XPS Spectrum
16. Identification of XPS Peaks
The plot has characteristic peaks for each element found in the surface of the sample.
There are tables with the KE and BE already assigned to each element.
After the spectrum is plotted we can look for the designated value of the peak energy
from the graph and find the element present on the surface.
Electronic Effect: Auger lines, Chemical shifts, X-ray satellites, X-ray “Ghost” and
Energy loss lines.
17. Advantages and Disadvantages
Advantages Disadvantages
Relatively Non-destructive technique.
Surface Sensitive (10-100Å).
Wide range of solids.
Quantitative measurements are
obtained.
Provides information about chemical
bonding.
Elemental mapping.
Limitations.
Very expensive technique.
High vacuum is required (UHV).
Slow processing (1/2 to 8
hours/sample).
Large area analysis is required.
H and He can not be identified.
Data collection is slow 5 to 10 min. Elemental mapping. Data collection is slow 5 to 10 min.
Poor spatial resolution.
XPS Technology
Consider as non-destructive.
Provide information about surface
layers or thin film structures
Applications in the industry:
Surface contamination, Tribological effects,
Polymer surface, Catalyst, Corrosion,
Adhesion, Semiconductors, Dielectric
materials, Electronics packaging, Magnetic
media, Thin film coatings and Depth
Profiling (Ar+ Sputtering)
18. [1] Siegbahn, K.; Edvarson, K. I. Al (1956). "β-Ray spectroscopy in the
precision range of 1 : 1e6". Nuclear Physics
[2] Turner, D. W.; Jobory, M. I. Al (1962). "Determination of Ionization
Potentials by Photoelectron Energy Measurement".
[3] journals.tubitak.gov.tr
[4] nanohub.org
[5] srdata.nist.gov
[6] www.eaglabs.com and www.files.chem.vt.edu
References
[6] www.eaglabs.com and www.files.chem.vt.edu
[7] Bio interface.org
[8] www.spectroscopynow.com
[9] www.surfaceanalysis.org
[10] www.csma.ltd.uk