Dr Ajit Kulkarni

Characterisation Tools for Nano @ IITB

Ajit Kulkarni I. I. T.-Bombay

Why this talk here? • Process may be based on a recipe – if it does not work, what next? • Or a new process is developed, how do you develop an understanding of the process? • Characterise the product, a material. • What do we mean by characterisation? • More difficult to define the question than to answer it • So once again…what is Characterisation?

Charcterisation of the UNKNOWN……material • Characterisation is the study of structure (including microstructure) and composition (including trace level). • Charcterisation makes use of one or more structure, composition-property correlation previously established. • Is it a catch-22 problem? – Or is it the limitation

Characterisation of Materials - composition, structure, microstructure, mapping • Philosophy – No characterisation is complete or absolute – Characterisation is not a goal unto itself. – Time, cost and need determine the methodology of characterisation along with its limitations. – One has to look for ‘IT’ to see it. One may see ‘IT’ if ‘IT is there. ‘IT’ can’t be seen if you don’t look for ‘IT’ even if it is there. One may not see ‘IT’ even if ‘IT’ is there, because it depends on how you look for ‘IT’.

Analysis - Probes and Signals What can be learnt from these signals? photons

EXCITATION

• bonding geometry of molecules • physical topography

EMISSION

ions

electrons

• chemical composition • chemical structure

Interaction with material

• atomic structure • electronic state TRANSMISSION

Probes and volume of interaction Volume of interaction depends on nature of probe (photon / electrons / ion) and its penetrability), sample(density), the way, the signal spreads laterally in the sample (scattering). Ultimately, this determines, lateral resolution and depth resolution for the analysis. Operating parameters of the instrument (acceleration voltage) alters energy of electrons and hence depth of interaction volume. In a scanning electron microscope, spot size or cross section of e-beam limits lateral resolution . In transmission electron microscope, the wavelength and the energy spread limits resolution. Of course, the instrument may set an upper limit. (aberrations) In ESCA, the escape depth of electrons determines the

Analytical Techniques – a comparison

Analytical Technique

IMS

Signal Measured

Elemental Range

H-U

Secondary Ions

Depth Resolution

5-30 Å

Surface info.

Chemical composition Chemical structure

OF-SIMS

Secondary Ions

H-U, Large Organic

2000 Å (Scanning Mode)

Adsorbate bonding

Molecules / Cluster Ions

EM

Transmitted Electrons X-Rays

Na-U EDX

N/A

E-SEM, EDX

Backscattered or

Na-U

1 - 5 micrometres

H- U

monolayer

Secondary Electrons and X-Rays

SS

Ions

atomic structure

on scattering spectroscopy)

ES/SAM

chemical composition Auger Electrons

Li-U

2-30nm

chemical composition

Li-U

5 - 30nm

chemical composition

uger electron spectroscopy, scanning Auger microscopy)

SCA/XPS

Photoelectrons

lectron spectroscopy for chemical analysis, X-ray photoelectron spectroscopy)

AIRS

IR photons

chemical structure

organic, some inorganics

monolayer

Adsorbate bonding

solid surfaces

upper most atoms

physical topography

eflection-absorption infra-red spectroscopy)

TM

-

canning tunnelling microscopy)

Analytical Technique

Signal Measured

Elemental Range

Depth Resolution

surface info,

Sample size, nature and the need for standards In TEM, ~3 mm diameter sample of a few hundred Å thick is studied. Does it represent the ‘bulk’. What is the effect of this sampling procedure? Surface and bulk analysis ? What you see on the surface need not represent bulk. ESCA / Auger looks at a few nanometer thick layers only. EDAX may look at signal averaged over a depth of one micron. Even exposure to air may add / modify the surface. Signal from one constituent may get altered by another constituent – interference Even microstructure can alter signal strength. Matrix effects – make things difficult to quantify Nearly identical standards are needed. Convenient for quality control in a plant. How about an R&D lab? Some times analysis of each sample is a research project.

Some jargons to remember Signal to noise ratio Background correction Spectral resolution (can be Mass resolution) Sensitivity Limit of detection Range of measurements Calibration Interference and Matrix effect Reference or standard No single technique can offer a universal solution.

Probe-material interaction –an example… X- ray as a probe X-rays in

photoelectrons out

KE

Sample Surface Layer φ

photon

valence band

Ev Ef BE

core levels

ding energy (eV) = photon energy - kinetic energy - work function BE (eV) = hν - KE – Φ asuring (signal) electron intensity and energy will give quantitative and alitative information

After Photoemission……

X-ray Fluorescence or Auger electron emission XRF/ EDAX / WDS / Electron probe micro analyser/AE

Fluorescence yield

Analytical tools based on above fundaes • • • •

Fluorescence X-rays (XRF) Diffracted X-rays (XRD) Emitted Electron (AES) Photoelectron (XPS)

X-ray Fluorescence Spectroscopy Emitted X-rays can be used to analyse the atom that is emitting Qualitatively and Quantitatively Triggering emission – signal it can be X-rays, electrons, Ions XRF EDS / WDS in SEM / EPMA/ TEM / STEM Ion probe microanalysis

In X-ray fluorescence measurements, intensity of characteristic radiation emitted by analyte atom is measured

Intensity of X-rays is a function of incoming signal intensity absorption cross section Fluorescence yield concentration of atoms in target self absorption Matrix effect when it is measured the Signal measured is a function of Detector characteristics Collection geometry

…Matrix effect

rface and Bulk Analysis – constraints A sample with a surface of size 1 cm2 - this will have ~ 1015 atoms in the surface layer. In order to detect the presence of impurity atoms present at the 1 % level, a technique must be sensitive to ca. 1013 atoms.

Contrast

this with a spectroscopic technique used to analyse a 1 cm3 bulk liquid sample i.e. a sample of ca. 1022 molecules. The detection of 1013 molecules in this sample would require 1 ppb (one part-per-billion) sensitivity - very

Surface Sensitivity of XPS

X-rays in

Photoelectrons out

d d = 3λ

Surface Sensitivity of XPS • The average distance from the surface a photoelectron can travel without energy loss is defined as the inelastic mean free pathlength (IMFP), λ . • Sampling depth, d, defined as the average distance from the surface for which 95% of photoelectrons are detected, d = 3λ .

‘universal curve’

X-ray Photoelectron spectroscopy is... Surface sensitive - photoelectron signal from first 1-10 layers of atoms and molecules. Quantitative. Provides insight into the chemical state of the element.  Sensitive - detection limit ~0.1 atomic %. Able to detect all elements except H and He.

Depth Profile through a TiN/SiO2 thin film on Si.

Si 2p region as a function of depth from the surface

• Si 2p region shows chemical environment of Si the Si atoms.

SiO2 TiN

Tools for better visionmicroscopy • Transmission Electron MicroscopeCM200 • FEGTEM-JEM2100F • CryoTEM*• FEGSEM- J7600F • ESEM*• IR microscope – • Confocal Laser Scanning microscope*

Sophisticated Analytical Instrument Facility

Instrument Details : Make :

PHILIPS

Model:

CM200

Specification : Operating voltages : 20-200kv Resolution : 2.4 Å

Applications : 

Materials Science/Metallugy biological Science



Nanotechnology



Ceramics



Pharmaceuticals



Semiconductors



Centre for Research in Nanotechnology & Science (CRNTS)

T E M

TEM images are formed using transmitted electrons (instead of the visible light) which can produce magnification details up to 1,000,000x with resolution better than 10 Å. Further more the analysis of the X-ray produced by the interaction between the accelerated electrons with the sample allows determining the elemental composition of the sample with high spatial resolution. Electron beam can be raster scanned over the sample and any signal generated can be measured as a function of beam position. .. Mapping of sample for Composition, morphology etc. (STEM)

On the anvil a new HRTEM (JEM 2100F) Field emission gun Higher brightness, 100 times greater than LaB6 gun Higher coherency Higher energy resolution, 0.7 to 0.8eV Higher resolution, increased contrast – lattice imaging STEM mode, EDS,

2Kx2K camera

27

JSM-7600F FEG SEM Scanning electron Microscope ☆High resolution ☆High stability ☆High productivity

Features of JEOL JSM 7600F • • • • •

Designed for Nano sciences In-Lens FE GUN Aperture angle optimizing lens Gentle Beam mode Specimen Airlock

Why you need low kV 20kV

5kV

15kV

3kV

Resolution of JSM-7600F Specimen: Evaporated gold on carbon

15kV

1kV

Ultra High Resolution by JSM-7600F

Platinum catalyst on carbon 　　 15kV, x500,000

Composition and mapping X-ray Fluorescence Spectrometer – Philips 400W Secondary Ion Mass Spectrometer- Phi-NanoTOF Induction Coupled Plasma Atomic Emission SpectrometerLaser ablation-ICP Mass Spectrometer EDS and WDS in electron microscopes (STEM, SEM) ESCA*

PHI nanoTOF TOF-SIMS

Secondary Ion Trajectories in TRIFT Analyzer ESA 3

ESA 2

Cs+, C60 +

Sampl e

SED

Pre-Spectrometer Blanker

PostSpectrometer Blanker

Energy Slit for Metastable Ion Rejection

Angular Acceptance ESA 1 Diaphragm

Detector Ga+, Aun+

User selectable angular acceptance diaphragm

Superior TRIFT Analyzer Imaging LMIG FIB cut and TOF-SIMS Images

Total Secondary Ion Image

Aluminum Ion Image

Silicon Ion Image

Only a PHI TRIFT analyzer can collect ions from the top surface and the perpendicular face of the FIB cut

representative of reflectron performance

The TRIFT analyzer is able to efficiently collect the secondary ions that are emitted at oblique angles (i.e. ions emitted more parallel to the substrate surface). The ability to collect obliquely-emitted secondary ions results in unequalled imaging performance. Oblique angular direction due to extraction field lines curving from the substrate over the In particle.

representative of TRIFT performance

TRIFT Adjustable Solid Angle of Acceptance Wide Collection Angle for Superior Imaging

Narrow Collection Angle for Best Mass Resolution

SiC Fiber 10µ m

10µ m

Tire Chord

100µ m

100µ m

“Turn Key” Charge Neutralization (A)

Low-energy Electron Beam

Analytical Ion Beam

Negative charge surrounding analytical zone repels electrons.

- - - - - - - - - - - - ++ - - - - - - - - - - Insulating Sample Sample Platen

(B)

Low-energy Electron Beam

Analytical Ion Beam

 Patented dual beam charge compensation has been used for many years on PHI XPS instruments.  The dual beam charge compensation method has proven successful at “turn key” insulator analysis.  The dual beam method allows electron energies below 10eV to be used, reducing sample damage.

Low-energy Ion Beam

 Inert gas ion energies (≤10eV) are below the damage threshold.

Insulating Sample Sample Platen

 Effective neutralization insulator imaging at magnifications.

enables higher

“Turn Key” Charge Neutralization Total Counts (0.0004 amu bin)

Sample: bulk PET 100 80 60

m/∆ m = 2,000

40 20 0

1200

Total Counts (0.0004 amu bin)

Improper charge neutralization. Ga+ dose = 2x1011 ions/cm2 raster size = 250 µ m 43 m/z of PET

1000 800 600

42.9

43.0

Proper charge neutralization. Ga+ dose = 2x1011 ions/cm2 raster size = 250 µ m 43 m/z of PET C2H3O

43.1

43.2

C3H7

m/∆ m > 9,000

400 200 0

CH3Si 42.9

43.0

m/z

43.1

43.2

“Turn Key” Charge Neutralization

Total Counts (0.0002 amu bin)

5000 4000

3mm thick polypropylene (PP) 100µ m x 100µ m raster area 10 minute acquisition

C2H5+

3000 2000

m/∆ m > 8,000 @ 29m/z

1000 0

28.95

29.00

29.05

29.10

Generation of 3D Isosurfaces and CrossSection Images Y

Z

Si

Si

Chemical and Biological tools Nuclear Magnetic Resonance Spectrometer Electron pin Resonance Spectrometer FTIR spectrometer Fluorescence Spectrometer CHSN analyser FACS Cell sorter Fluorescence Microscope Tissue culture laboratory

Other MaterialsCharacterisation tools Thermogravimetry, Differential Thermal analyser Differential Scanning calorimeter Image analyser with Optical Microscope –polariser, DIC etc

Confocal Laser Raman Spectrometer – Photoluminescence Spectrometer Dynamic Light scattering- particle size analyser Zeta Potential measuring unit

Centre for Research in Nanotechnology & Science (CRNTS)

Instrument Details : Make : Thermo finnigan, Italy Model : FLASH EA 1112 series Specification : Estimation of CHN/CHNS/O in percentage level to high concentration level.

The

CHNS(O) Analyzer find utility in determining the percentages of Carbon, Hydrogen, Nitrogen, Sulphur and Oxygen of organic compounds, based on the principle of "Dumas method" which involves the complete and instantaneous oxidation of the sample by "flash combustion". The combustion products are separated by a chromatographic column and detected by the thermal conductivity detector (T.C.D.), which gives an output signal proportional to the concentration of the individual components of the mixture.

Centre for Research in Nanotechnology & Science (CRNTS)

Instrument Details : Make :

VARIAN, USA

Model:

E-112 ESR Spectrometer

Specification : X-band microwave frequency (9.5 GHz) Electron Spin resonance spectroscopy is based on the absorption of microwave radiation by an unpaired electron when it is exposed to a strong magnetic field. Species that contain unpaired electrons (namely free radicals, odd-electron molecules, transition metal complexes, rare earth ions, etc.) can therefore be detected by ESR. Electron Spin Resonance, ESR, is a powerful non-destructive and non-intrusive analytical method. ESR yields meaningful structural information even from ongoing chemical or physical processes, without influencing the process itself. It is the ideal technique to complement other analytical methods in a wide range of application areas.

Applications :  Molecular structure

 Relaxation properties

 Crystal structure

 Electron transport

 Reaction kinetics

 Crystal / ligand fields

 Valence electron wave functions

 Reaction mechanisms etc.

 Molecular motion

Centre for Research in Nanotechnology & Science (CRNTS)

Instrument Details : Make : Nicolet Instruments Corporation, USA Model: MAGNA 550 Specification : Range - 4000 cm-1 to 50 cm-1 Infrared Spectroscopy gives information on the vibrational and rotational modes of motion of a molecule and hence an important technique for identification and characterisation of a substance.. The Infrared spectrum of an organic compound provides a unique fingerprint, which is readily distinguished from the absorption patterns of all other compounds; only optical isomers absorb in exactly the same way. Hence FTIR is an important technique for identification and characterization of a substance.

Applications :  Chemistry & Chemical Engineering  Polymer & Rubber Industries  Forensic Labs  Pharmaceutical Labs  Nanotechnology

 Food Industries  Agriculture  Petroleum  Industries

Sophisticated Analytical Instrument Facility

Instrument Details : Make : VARIAN, USA Model: Mercury Plus 300MHz NMR SPECTROMETER Specification : 5mm Autoswitchable probe with PFG (1H/ 13C/ 31P/ 19F) 5mm Dual Broad Band probe with PFG for Multinuclear NMR (13C, 15N, 27Al, 31P, 29Si, 77Se, 119Sn, 125Te, 199Hg, 51V, 7Li etc.) Nuclei with non-zero spins, when placed in a strong magnetic field precess at specific orientations with respect to the applied magnetic field. When appropriate energy is supplied in the form of radio frequency, these nuclei flip to a higher energy state. The energy absorbed during this transition is a function of nucleus type and its chemical environment in the molecule The excited nuclei are allowed to precess freely and come back to their equilibrium positions. During this process an electric signal is induced in a suitably placed RF coil. This signal which is monitored with respect to time is called free induction decay (FID). The FID, which is in time domain gives its equivalent frequency domain signal on Fourier transformation. A plot of the absorption frequency versus the intensity of the absorption constitutes the NMR spectrum.

Centre for Research in Nanotechnology & Science (CRNTS)

Instrument Details : Make : PHILLIPS (now, PANAlytical, The Spectris Technology, The Netherlands) Model: PW 2404 Specification: X-Ray tube with Rh target.

X-ray generator: 4 KW with 60 KV, 125 mA (in steps). The generator is solid state based on 'Switch Mode Power Supply' design to respond fast the changes sought in X - Ray tube power.