This document discusses laser ablation and pyrolysis techniques. It begins by introducing lasers and their various types and uses. It then describes laser ablation, which is the process of removing material from a surface using a laser beam. Pulsed laser ablation is discussed as a method to machine materials with high precision without causing heat damage. Laser pyrolysis is then covered, which uses high heat from a laser to decompose mixtures of reactants and gases to produce nanoparticles. Specific techniques like pulsed laser deposition and laser beam interference ablation are also summarized.

1. Laser ablation and Pyrolysis
Jaismon Francis
NIT Calicut

2. Table of content
1. Lasers
1.1 Intensity of Laser radiation
1.2 Different types of lasers and its uses
1.3 Thermal processing of materials using laser
2. Laser ablation
2.1 Cold machining by a continuous wave laser
2.2 Definition of laser ablation
2.3 Laser ablation by a pulsed laser
2.4 Pulsed laser ablation for production of nanoparticles
2.5 Pulsed laser deposition
2.6 Laser beam interference ablation
3. Laser Pyrolysis
3.1 Process of Laser pyrolysis
3.2 Laser pyrolysis for production of nanoparticles

3. Intensity of Laser Light: Comparison with Sun light
Intensity of
Sunlight at
earth
surface=.105
Watts/𝒄𝒎 𝟐
Intensity of
typical pulsed
laser light is
approximately
10^10
Watts/𝒄𝒎 𝟐
 Laser Light is 100000000000 times intense than Sunlight !!!!

4. lasers
 Cutting
 Slicing
 Drilling
 Welding
 Surface modification
Laser processing is very mature technology now
 Nd:Yag
 CO2
 Excimer
 Ti:Sapphire
 Cu vapour lasers
Uses of laser in industry Type of lasers used for processing
Conventional laser machining is thermally based processing

5. Laser light for nano-microfabrication
Thermal processing cause inevitably scorching and rugged edges
Fig. A 25micron trench machined by a laser beam over a 1mm thick Ni-Fe alloy substrate
It will become a critical issue in nanofabrication using lasers

6. Laser ablation or cold machining by a laser beam
clean cut pattern edge and smooth machined surface
Short wavelength photons from a laser can excite a photochemical reaction
in some macromolecule based materials, which can cause breaking up of
long molecule chains and polymer is directly vaporised without melting
phase
Fig. Examples of polymer microstructures made of direct laser ablation

7. Laser ablation
Laser Ablation
Image Cortesy; Wikipedia
 Laser ablation or photo ablation is the process of removing material
from a solid (or occasionally liquid) surface by irradiating it with
a laser beam.

8. Pulsed laser ablation
Ref :oxforddictionaries.com
 A significant development of laser ablation is application of femto
second lasers
 Femtosecond laser is so short when shining on material surface that
laser energy has no time to convert into heat diffusing into adjacent
area
 Material is directly converted from solid state to plasma state and
burst out of surface with out melting

9. ZnSe nanocrystals synthesis by laser ablation technique
ZnSe nanocrystals
1 wt % PVP in DMF
Focused beam
532nm Nd:YAG laser pulse
Figure .This picture depicts how ZnSe nanocrystals are formed by laser ablation of bulk ZnSe in DMF-PVP solution
F. Mosmer, Optical properties of ZnSe nanocrystals synthesized y laser ablation technique

10. Nano Fabrication using Pulsed laser ablation
Materials that can be processed: glass, plastics, metals, semiconductors.
Generation of Au colloidal nanoparticles in water, Si wafer cleaving.
Image Cortesy; Wikipedia
Fig. Selective ablation of CIGS – Mo
line in the center
Fig. Deep trenches in Ta slab

11. Pulsed Laser Deposition
Laser Ablation for nanofabrication
Image Cortesy; Wikipedia
 Pulsed laser deposition is a thin film deposition technique where a
high power pulsed laser beam is focused inside a vacuum chamber to
strike a target of the material that is to be deposited

12. Laser Beam Interference Ablation (LBIA)
Laser Ablation for nanofabrication
Image Cortesy; Wikipedia
 Laser Beam Interference Ablation (LBIA) combines multiple las
er beams to create a spatial interference pattern. The interference
effect allows reducing feature dimensions to below the diffraction
limit, Multi-beam parallel processing for periodic structures.
 LBIA is used for 2D patterning of thin films and surfaces and
surface modification. Min period 600 nm using 532 nm wavelength,
with uniform spacing within the laser spot size of ~50um

13. Laser Beam Interference Ablation (LBIA)
Image Cortesy; Wikipedia
Fig. Laser beam interference ablation setup

14. Nano Fabrication using LBIA
Materials that can be processed: Chromed glass, Au, Cu, Si, Al,
Image Cortesy; Wikipedia
Fig. Net-like structure produced in
Cr film with single pulse ablation.
Bright areas – remaining metal.
Fig. Six laser beam interference
ablation of 200 nm Pt film

15. SN TECH
NIQUE
MINIMUM
FEATURE
SIZE
WORKING
AREA
PROCESS SPEED APPLICATIONS
1 Laser Direct
Writing (LDW)
3-5 μm 200×200
mm2
Up to 2 m/s with
XYZ stages; 20
m/s with
galvoscanners
Thin-film
structuring. Selective
and localized
modifications of
surface.
2 Ultrashort
Pulse
Laser Ablation
(ULA)
15 μm Material
dependent
1000-
100000 μm3/s
Material
dependent 1000-
100000 μm3/s
3D microfabrication;
micromoulds.
Microfluidics
3 Laser Beam
Interference
Ablation
(LBIA)
Period ~
wavelength;
100-200 nm
0.5×0.5 mm2 1000 μm2/shot 2D patterning of thin
films and surfaces;
surface
modification.

16. Laser Pyrolysis
Ref :oxforddictionaries.com
 Decomposition brought about by high temperatures
Pyrolysis

17. Laser Pyrolysis
Fig.condensable products result from laser induced chemical reactions at the crossing
point of the laser beam with the molecular flow of gas or vapour–phase precursors

18. Laser Pyrolysis for production of nanoparticles
Ref :en.oxforddictionaries.com
Laser Pyrolysis
 Decomposition brought about by high temperatures
 A technique used to synthesize ultrafine powders(nanoparticles) by
heating a mixture of reactant vapour and inert gas with a laser.
 condensable products result from laser induced chemical reactions at
the crossing point of the laser beam with the molecular flow of gas or
vapour–phase precursors
 The literature reports the possibility to produce carbides, nitrides,
oxides, metals and composites nanoparticles by this process

19. Jaismon Francis
23rd October ,2018
NITC
THANK YOU