Pulsed Laser Deposition of Tungsten Thin Films Poster W… · Pulsed Laser Deposition of Tungsten...
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Pulsed Laser Deposition of Tungsten Thin Films Kassem W., Tabbal M., Antar G., Roumie M. † Department of Physics, American University of Beirut, Beirut, Lebanon † Lebanese Atomic Energy Division, CNRS, Beirut, Lebanon Deposition - nucleation Resputtering - implantation Increasing laser energy increases kinetic energy of species by laser supported absorbtion 50 - 100 eV ions 5 - 10 eV atoms + + + Screening - no deposition Plasma species energy low energy atoms Increasing Argon pressure leads to a decrease in the kinetic energy of the plasma species Surface modification of growing film by applying a substrate temperature sputtering threshold crystallization 0 Argon gas Tungsten ions KrF excimer laser 20 ns 248 nm Growth Temperature A clear difference in crystal structure is shown for dif- ferent growth tempera- tures Sharper peaks indicate larger grains, improved grain bound- aries and less internal strain RBS results show no sign of interdiffusion or detectable impu- rutues Increased laser fluence shows im- proved crystal structure, with proper- ties similar to the bulk Film thickness has an exponential growth with deposition rates reaching 2nm/min AFM images confirm XRD results indicat- ing control- lable change in film mor- phology Deposition Time: 3hrs Pressure = 10mTorr Temp = 450C a b c d Laser Fluence Pressure regimes vary from a screening effect to a sput- tering effect. Film morphology can be thus tuned to maximize deposition rate and tune film stress with the so called “shot-peening” model Energy = 500mJ Temp = 450C I I II II Growth Pressure *[email protected] Conclusions Acknowledgments Future Prospects Wide range of growth regimes available to PLD: implantation, shot- peening effects, aggregation. Deposition parameters show direct effect on film properties such as crystalline phase and structure. Laser fluency is seen to increase deposition at an exponential rate, which is an important issue should the coating process need to be scaled up A thorough determination of stress in the films deposited as well as texture and preferred grain orientation. The development of more Tungsten coatings on graphite pucks with thickness over 3um This work was supported and funded by the Lebanese CNRS 2nd International School "Laser-surface interactions for new materials production: tailoring structure and properties" Objective and Motivation To study the effets of deposition parameters on the structure of the grown film, and tailor it towards specific applications in fusion technology. PLD is a non-thermal method capable of creating ablated species with high kinetic energies (50-100eV) offering novel growth regimes. Fusion tokamaks such as ASDEX and JET are utilizing graphite coated Tungsten tiles as plasma-facing components. Till now there have been scarce reports on the growth of Tungsten by PLD Target is shielded from laser pulse by the nascent plasma after the first few ns
Transcript of Pulsed Laser Deposition of Tungsten Thin Films Poster W… · Pulsed Laser Deposition of Tungsten...
Pulsed Laser Deposition of Tungsten Thin Films Kassem W., Tabbal M., Antar G., Roumie M.†
Department of Physics, American University of Beirut, Beirut, Lebanon†Lebanese Atomic Energy Division, CNRS, Beirut, Lebanon
Deposition -nucleation
Resputtering - implantation
Increasing laser energy increaseskinetic energy of species by laser supported absorbtion
50 - 100 eV ions5 - 10 eV atoms
+ + +
Screening - no deposition
Plasma speciesenergy
low energy atoms
Increasing Argon pressure leads to a decrease in the kinetic energy of the plasma species
Surface modi�cation of growing �lm by applying a substratetemperature
sputtering thresholdcrystallization
0
Argongas
Tungstenions
KrF excimer laser
20 ns248 nm
Growth Temperature
A clear di�erence in crystal structure is shown for dif-ferent growth tempera-tures
Sharper peaks indicate larger grains, improved grain bound-aries and less internal strain
RBS results show no sign of interdi�usion or detectable impu-rutues
Increased laser �uence shows im-proved crystal structure, with proper-ties similar to the bulk
Film thickness has an exponential growth with deposition rates reaching 2nm/min
AFM images con�rm XRD results indicat-ing control-lable change in �lm mor-phology
Deposition Time: 3hrsPressure = 10mTorrTemp = 450C
ab
c d
Laser Fluence
Pressure regimes vary from a screening e�ect to a sput-tering e�ect. Film morphology can be thus tuned to maximize deposition rate and tune �lm stress with the so called “shot-peening” model
Energy = 500mJTemp = 450C
I
I
II
II
Growth Pressure
Conclusions
Acknowledgments
Future ProspectsWide range of growth regimes available to PLD: implantation, shot-peening e�ects, aggregation.
Deposition parameters show direct e�ecton �lm properties such as crystalline phase and structure.
Laser �uency is seen to increase deposition at an exponential rate, which is an important issue should the coating process need to be scaled up
A thorough determination of stress in the �lms deposited as well as texture and preferred grain orientation.
The development of more Tungsten coatings on graphite pucks with thickness over 3um
This work was supported and funded by the Lebanese CNRS
2nd International School"Laser-surface interactions for new materials production: tailoring structure and properties"
Objective and Motivation
To study the e�ets of deposition parameters on the structure of the grown �lm, and tailor it towards speci�c applications in fusion technology.
PLD is a non-thermal method capable of creating ablated species with high kinetic energies (50-100eV) o�ering novel growth regimes.
Fusion tokamaks such as ASDEX and JET are utilizing graphite coated Tungsten tiles as plasma-facing components.
Till now there have been scarce reports on the growth of Tungsten by PLD
Target is shielded from laser pulse by the nascent plasma after the �rst few ns
