BIOMATERIAL

[XRD and FTIR analysis]

Nur Istianah, ST.,MT.,M.Eng

ISSUES TO ADDRESS...ISSUES TO ADDRESS...ISSUES TO ADDRESS...ISSUES TO ADDRESS...

• Historical retrospective

CHAPTER 3: CRYSTAL STRUCTURESXX--Ray Diffraction (XRD)Ray Diffraction (XRD)

• Historical retrospective

• Henry Bragg Equation

• XRD-analysis

• How to read XRD patterns?

• Exclusions

• What questions can be answered by XRD method?

Definition

• XRD is a non-destructive analytical technique which

reveals information about the crystallographic

structure and physical properties of materials ranging

from simple inorganic solids to complexfrom simple inorganic solids to complex

macromolecules.

Scale of Structure OrganizationScale of Structure Organization

A single crystal specimen in a Bragg-Brentano diffractometer

would produce only one family of peaks in the diffraction pattern.

2θθθθ

At 20.6 °2 θ, Bragg’s law fulfilled for the (100) planes, producing a diffraction peak.

The (110) planes would diffract at 29.3 °2 θ; however, they are not properly aligned to produce a diffraction peak (the perpendicular to those planes does not bisect the incident and diffracted beams). Only background is observed.

The (200) planes are parallel to the (100) planes. Therefore, they also diffract for this crystal. Since d200 is ½ d100, they appear at 42 °2 θ.

A polycrystalline sample should contain thousands of crystallites.

Therefore, all possible diffraction peaks should be observed.

2θθθθ 2θθθθ 2θθθθ

• For every set of planes, there will be a small percentage of crystallites that are properly oriented to diffract (the plane perpendicular bisects the incident and diffracted beams).

• Basic assumptions of powder diffraction are that for every set of planes there is an equal number of crystallites that will diffract and that there is a statistically relevant number of crystallites, not just one or two.

Example: Diffraction Patterns

• Each peak represents the solution to Bragg’s law for known radiation

wavelength (λ = 0.154nm)

• The unique relationship between such patterns and crystal structures

provide a powerful tool for identification of the phase composition of

powders and polycrystalline materials.

XX--Ray Diffractometer (XRD) Ray Diffractometer (XRD)

XRD is a system of the highest quality used to:

Characterize the crystallographic structure, crystallite size (grain size), and preferred orientation of our biomaterials.

Characterize heterogeneous solid mixtures to

D8 DISCOVER, Bruker AXS Inc. (Madison, WI USA)

Characterize heterogeneous solid mixtures to determine relative abundance of crystalline compounds.

Determine strains in our crystalline materials.

Solve the complete structure of our materials.

Provide structural information on unknown materials.

FTIR application

• What is FTIR?

• Applications of FTIR (general)

• Applications of FTIR for semiconductor industry• Applications of FTIR for semiconductor industry

• Remarks

FTIR

• Fourier Transform Infrared Spectroscopy

• Used for identifying or characterizing organic (and

some inorganic) compounds (solid, powders, some inorganic) compounds (solid, powders,

residues, solvents, liquids, gas)

• IR radiation is absorbed/transmitted; resulting

spectrum characteristic of molecular structure

FTIR

• “Fingerprint” type method (no 2 are same)

• Detection of individual chemical compounds or characteristic absorptions of chemical functional groups (organic and some inorganic)

Detection limit: picogram range (monomolecular • Detection limit: picogram range (monomolecular layers detectable on metal surfaces)

• Qualitative, quantitative

• Reference libraries, spectral interpretation

• Sampling techniques: transmission, external reflection, internal reflection (ATR), diffuse reflection, emission, and photoacousticspectroscopy

• Detectors: triglycine sulfate (TGS), mercury-cadmium-telluride (MCT)

Theory and Instrumentation

• Light enters the spectrometer and is split by the beam splitter. The figure

above shows what is referred to as the Michelson interferometer

Theory and Instrumentation(contd.)

• The light originates from the He-Ne laser

• Half of the light is reflected 90 degrees and hits a fixed

mirror, while the other half passes through the beam

splitter and hits the moving mirrorsplitter and hits the moving mirror

• The split beams are recombined, but having traveled

different distances, they exhibit an interference pattern

with each other

• As they pass through the sample, the detector collects the

interfering signals and returns a plot of response v. mirror

displacement known as an interferogram

FTIR with microscope

Applications

Applications are vast and diverse.Some of them are

•Compositional analysis of organic,inorganic and

polymers

•Biological and biomedical fields like detection of water

in biological membranesin biological membranes

•Analysis of Aircraft exhausts

•Measurement of toxic gas in fuels

•Combustion

•Gas analysis

• and lots more

General Applications

• Identify unknown compounds

-e.g. plastics, drugs (i.e. cocaine),

contamination (i.e. flux residues,

silicone, esters, grease, etc.)silicone, esters, grease, etc.)

• Obtain structural information (organic functional groups)

-e.g. alkanes, alkenes, alkynes, aromatics, alcohols,

ethers, amines, aldehydes and ketones,

carboxylic acids, amides, etc.

Common uses in semiconductor industry• Determination of interstitial oxygen and substitutional carbon in

processing wafers

• Epitaxial film thickness measurements

• Monitoring phosphorus in phosphosilicate thin films and both phosphorus and boron in borophosphosilicate thin filmsphosphorus and boron in borophosphosilicate thin films

• Measurement of the hydrogen content in oxide and nitride thin films

• Identification of particles and residues (most common)

• Incoming materials characterization

• Trace gas analysis

• Carrier concentration measurements

• Characterization of Si surfaces after cleaning operations

Measurement of Interstitial Oxygen and Substitutional Carbon in

Si Wafers

• Si-C, Si-O-Si

Advantages of FTIR for measurement of Cs and Oi

• Non-destructive

• Cheaper

• Faster• Faster

• Reproducible

• Sensitive (to dopants)

• Excellent spatial resolution (5-10 um)

• Specific to the Oi and Cs in Si

Epitaxial Film Thickness Applications

• To determine epitaxial (Epi) layer film thickness (the most commonly used high-resistivity Epi layers are transparent to IR radiation)

• 3 methods (constant-angle observations making use • 3 methods (constant-angle observations making use of either direct or modified measurement of interference phenomena):

1) Interferogram Subtraction

2) Constant Angle Reflection Interference Spectroscopy

3) Cepstrum

Constant Angle Reflectance Interference

Advantages of FTIR for Epi thickness measurements

• speed of measurement

• Non-destructive

• Reproducible• Reproducible

• Lends itself to automation

• Operator independent

Particle/residue identification in Failure Analysis

Advantages and Disadvantages

• FT – IR can take wavelength readings across the whole IR region simultaneously and smoothly, making this a very rapid technique.

• The technique is non-invasive and non-destructive. Its resolution of .125 cm-1 is not spectacular in comparison to other vibrationaltechniques and it will not give the same detailed structural information that NMR, MS, or X-ray crystallography.information that NMR, MS, or X-ray crystallography.

• IR spectroscopy is notoriously sensitive to the absorption of water, and it has the tendency to overwhelm all of the other peaks. If there is significant moisture in the sample the penetration distance of the light decreases. It may be advantageous to go with Raman in place of IR in the case of excess moisture.

• Spectra in the frequency domain can never be eyeballed conclusively. They are always subject to some sort of manipulation, leading some to believe that the data can say whatever the experimenter wants it to say depending on how it is manipulated.

Remarks

• Many applications

• May use other instruments/tools/techniques to

obtain additional information or confirmationobtain additional information or confirmation

• Relatively cheap, quick, accurate, internally

calibrated (self-calibrated)

• Even with software and automation, still recommend

a chemist familiar with spectral interpretation

THANK YOU