1. UNIVERSITÀ DEGLI STUDI DI MILANO BICOCCA Facoltà di Scienze Matematiche Fisiche e Naturali Corso di Laurea in Scienze Orafe
Laser Induced Forward Transfer (LIFT) for applications In jewellery industry
Relatori
Prof. Dimitri Batani
Prof.ssa Maria Luisa Vitobello
Prof. Yas AL-Hadeethi
Saad Altarazi
Anno accademico 1

2. Laser Induced Forward Transfer LIFT
Laser induced forward transfer (LIFT) was first demonstrated by Bohandy et al in 1986.
LIFT has three phases:
A laser pulse impinges on a donor film
It vaporizes a portion of the metal film. Plasma expansion ejects a piece of donor film at high velocity
The ejected film is in the form of micron-sized clusters and bonds with the acceptor substrate
Schematic of the transfer principal 2 2

3. LIFT APPLICATIONS LIFT applications :
Deposition method in direct writing of metalic film.
Hydrogen-assisted laser-induced forward transfer.
Matrix-assisted pulsed laser evaporation/direct-write.
Laser-induced thermal imaging (LITI).
Microprinting for Electronics and Optoelectronics.
Conventional Pattern Transfer Processes.
Laser Printing for Organic and Polymers for Optoelectronics.
Laser Printing of Biomaterials. 3

4. Examples of succesful doposition of LIFT4

5. Comparison of LIFT and PLD
Pulsed Laser Deposition (PLD)‏
A laser beam of high intensity is focused on a target. An expanding coating plume is created and subsequently condenses on a substrate
LIFT :
LIFT is a micro printing technique. It can be considered as inverse technique of micromachining. LIFT adds mass instead of removing mass
LIFT as compared to PLD:
Both techniques able to deposit a large variety of materials.
Both able to preserve the stochiometric ratio of the material.
LIFT is more directional as compared to PLD.
LIFT has colder impact than PLD.
Lower intensity and larger spot size required with LIFT. 5

6. GOAL OF OUR WORK
In this research, we achieved controlled transfers of thin films of different metallic materials to a receiving substrate for possible applications in the jewellery industry
Study the performance of LIFT with lasers working in the green and pulses of ps duration. 6

7. Frequency doubeld , Nd YAG Laser λ=532nm Pulse duration t≈40ps
Fluence F≈10J/cm2
Single pulse on target
Reptition rate 2Hz
Energy E≈20mJ 7

8. Substrate was parallel, at a close proximity to the thin film.
It was possible to horizontally and vertically move this thin film and the receiving substrate in order to expose fresh areas every time.
Optical and SEM images as well as EDAX spectra showed evidence of the production of micrometric scale pattern of many different materials on substrates 8

9. TYPICAL RESULTS: OPTICAL MICROSCOPY
Optical microscope image of Al deposited on Agate
Optical microscope image of Au deposited on Ag 9

10. EDAX spectrum showing deposition on Agate with evidence of Al deposits
TYPICAL RESULTS: SEM & EDAX Si Al . Si
EDAX spectrum showing deposition on Agate with evidence of Al deposits 10

11. . Typical results: SEM & EDAX SEM image showing Au deposited on Ag Au
EDAX spectrum of Au deposited on Ag 11

12. EFFECTS OF VARIOUS PARAMETERS
We performed several experiments changing the substrate and/or the thin foil and/or the foil thickness and/or the laser energy.
All experiments were conducted in air at room temperatures.
In all experiments the film was in close contact with substrate.
A sticking tape was applied on the deposited material as a simple test of adhesion. 12

13. Thin foils provide better adhesion
Sr. #.
Foil Thickness (um)‏
Substrate
Material
Remarks/
Adhesion 1. 1 Cu
good 2. Si 3. Ni 4. Pb 5. Pd
small deposition 6. Zn 7. 4 Ag 8.
quartz
Nothing deposited 9.
SiO2
Poor adhesion
10. 5
malachite
Transfer
of Au foil
Sr. #.
Foil Thickness (um)‏
Substrate Material
Remarks 1. 1 Sn
good 2. 4
SiO2
Poor adhesion
Transfer
of Cu foil
Thin foils provide better adhesion 13

14. EFFECT of the Substrate (4µm Foils)‏
Sr #.
Foil
Substrate
Adhesion 1. Al
SiO2
Good 2. Si 3. Cu 4. Zn 5.
Quartz
Nothing 6. Au
Silver 7. 8.
Poor 9.
Malachite
Al shows a good adhesion on all substrate except (crystalline ) quartz
Au shows good adhesion only on metal substrate 14

15. Effect of foil separation
Effect of laser energy
With lower energy of 2mJ, LIFT deposited Al on Agate, Au on Ag, Al on Si but with poor adhesion to the substrates.
Effect of foil separation
Better adhesion with close contact as compared to 1mm separation 15

16. A PHYSICAL MODEL FOR LIFT
Laser-target interaction: Plasma expands (ablation) and shock wave travels inside target.
Ablation pressure induces acceleration
Accelerated target travels towards the substrate
Target-Substrate interaction:
Pressure on substrate at impact depends on target velocity 16

17. We developed a simple analytic model
for LIFT
ILP [ Scaling Laws] High Intensity I~1011 W/cm2 (experimental parameter) High Pressure P~Mbar
P TFoil (Equation of state (EOS) model: SESAME table)‏
Pvf Foil target velocity
vf  pressure at impact calculated from momentum conservation
Temperature inside target and substrate (from EOS)‏ 17

18. Results of model 18

19. EXPERIMENTAL RESULTS VS MODEL
Il modello analitico ci permette di studiare l’ influeza dei parametri fisici nel processo lift, in particolare :
Foglio da 1 microno piu veloce quello di 4 micron
Al meglio di Au
buona adesione grazie alle alte pressioni raggiunte sul substrato (p 10-100Kbar). 19

20. Conclusions
Results show that LIFT enabled the controlled transfer of a thin film of many materials from carriers to receiving substrates on a micrometric scale as proven by SEM and EDAX analysis.
--It can be achieved using single pulses of laser. First LIFT work with green laser in the ps regime.
--In some cases, strong adhesion of the deposition on the substrate was observed. In other cases instead complete removal of the metal film across the whole irradiated area was possible without any damage of the underlying substrate.
--Moreover we developed a simple physical model in order to study in a more detailed way the influence of each parameters involved in the system (target velocity, laser-induced pressure, foil induced pressure, foil and substrate densities...) on LIFT performance.
--We successfully transferred precious materials on substrate of interest for the jewellery industry 20

21. Thanks for Your Time & Patience21