Self-organization in thin metal films under laser irradiation ; Plonų metalų sluoksnių savitvarkos lazerio spinduliuotės poveikyje tyrimas ir modeliavimas
99 pages

Self-organization in thin metal films under laser irradiation ; Plonų metalų sluoksnių savitvarkos lazerio spinduliuotės poveikyje tyrimas ir modeliavimas

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Publié par
Publié le 01 janvier 2011
Nombre de lectures 51
Poids de l'ouvrage 5 Mo

Exrait

VILNIUS UNIVERSITY
CENTER FOR PHYSICAL SCIENCES AND TECHNOLOGY
INSTITUTE OF PHYSICS
Mindaugas Gedvilas
SELF-ORGANIZATION IN THIN METAL FILMS UNDER LASER
IRRADIATION
Doctoral dissertation
Technological Sciences, Material Engineering (08T)
Laser Technology (T165)
Vilnius, 2011 The research was performed in the Institute of Physics of Center for Physical
Sciences and Technology in 2006-2011.
Scientific supervisor:
Dr. Gediminas Raiukaitis (Institute of Physics of Center for Physical Sciences
and Technology, technological sciences, material engineering - 08T, laser
technology - T165). VILNIAUS UNIVERSITETAS
FIZINI IR TECHNOLOGIJOS MOKSL CENTRO
FIZIKOS INSTITUTAS
Mindaugas Gedvilas
PLON METAL SLUOKSNI SAVITVARKOS LAZERIO
SPINDULIUOTS POVEIKYJE TYRIMAS IR MODELIAVIMAS
Daktaro disertacija
Technologijos mokslai, Medžiag inžinerija (08T)
Lazerin technologija (T165)
Vilnius, 2011 Disertacija rengta 2006-2011 metais Fizini ir Technologijos Moksl Centro
Fizikos institute.
Mokslinis vadovas:
Dr. Gediminas Raiukaitis (Fizini ir technologijos moksl centro Fizikos
institutas, technologijos mokslai, medžiag inžinerija - 08T, lazerin
technologija - T165). CONTENTS
ACKNOWLEDGMENTS ................................................................................ 7
LIST OF ABBREVIATIONS .......................................................................... 8
1 INTRODUCTION .................................................................................. 11
1.1 THE AIM OF THE RESEARCH ............................................................... 12
1.2 PRACTICAL VALUE AND NOVELTY .................................................... 12
1.2.1 The novelty of the thesis ............................................................... 12
1.2.2 The practical value of the thesis ................................................... 13
1.3 STATEMENTS TO BE DEFENDED ......................................................... 13
1.4 APPROBATION ................................................................................... 14
1.4.1 Scientific papers ............................................................................ 14
1.4.2 Conference presentations .............................................................. 17
1.5 CONTRIBUTIONS ................................................................................ 22
1.5.1 Author’s contribution .................................................................... 22
1.5.2 Coauthors’ contribution ................................................................ 22
2 LITERATURE REVIEW...................................................................... 24
2.1 LASER-INDUCED PERIODIC SURFACE STRUCTURES AND RIPPLE TYPES
24
2.1.1 Interference between an incident beam and surface scattered
waves 24
2.1.2 Laser-induced stress-related instabilities in metal films............... 26
2.1.3 Instabilities during laser direct writing ......................................... 27
2.1.4 Explosive crystallization ............................................................... 28
2.2 MECHANICALLY AND THERMALLY INDUCED RIPPLES ...................... 29
2.2.1 Marangoni convection in liquid metal .......................................... 29
2.2.2 Plateau–Rayleigh instability ......................................................... 30
2.2.3 Spinodal dewetting ....................................................................... 31
2.2.4 Saffman-Taylor instability ............................................................ 33
2.2.5 Fingering instability ...................................................................... 34
2.2.6 Buckle morphology of compressed films ..................................... 35
2.2.7 Periodical thin film fracture .......................................................... 37
2.3 LIGHT MATTER INTERACTION ............................................................ 38
2.3.1 Absorption of laser radiation ........................................................ 38
2.3.2 Heat transfer equation ................................................................... 40
2.3.3 Ablated crater diameter and hole depth ........................................ 41
2.4 LASER-INDUCED STRUCTURES IN CHROMIUM FILM........................... 42
2.4.1 Chromium ablation with an astigmatic beam ............................... 44
2.5 PHYSICAL PROPERTIES OF CHROMIUM .............................................. 45
2.6 PHYSICAL PROPERTIES OF METALS .................................................... 47
2.7 PHYSICAL PROPERTIES OF GLASS ...................................................... 48
3 EXPERIMENTAL SET-UPS AND PROCEDURES ......................... 49
3.1 EXPERIMENTAL SET-UP ..................................................................... 49
53.2 EXPERIMENTAL ABLATION THRESHOLD OF THIN METAL FILMS ........ 50
3.3 GRATING CHARACTERIZATION SET-UP .............................................. 52
4 RIPPLE FORMATION IN THIN CHROMIUM FILM ................... 53
4.1 FILM ABLATION WITH NON-OVERLAPPING LASER PULSES ................ 53
4.2 FILM ABLATION WITH OVERLAPPING LASER PULSES ......................... 54
4.2.1 Quasi-periodical fracture .............................................................. 54
4.2.2 Periodically molten resolidified lines ........................................... 55
4.2.3 Ripple formation ........................................................................... 55
4.2.4 Initial stage of ripple formation .................................................... 56
4.2.5 Process window for the ripple formation ..................................... 57
4.2.6 Reconstruction of ripples after a defect ........................................ 59
4.2.7 Crack propagation in metal film ................................................... 60
4.3 CONCLUSIONS ................................................................................... 61
5 FABRICATION OF PERIODICAL GRATINGS .............................. 62
5.1 PERIODICAL GRATING FABRICATION ................................................. 62
5.2 CHARACTERIZATION OF GRATINGS ................................................... 63
5.3 CONTROLLING THE GRATING PERIOD ................................................ 64
5.3.1 Grating period vs laser fluence ..................................................... 65
5.3.2 Grating period vs shift between pulses ......................................... 66
5.4 CONCLUSIONS ................................................................................... 66
6 CASE OF OTHER METALS: LASER IRRADIATION OF
ALUMINUM, COPPER, GOLD AND SILVER FILMS ........................... 68
6.1 NO RIPPLES IN ALUMINUM ................................................................ 68
6.2 DEWETTING IN THIN COPPER FILM .................................................... 68
6.3 THREE KINDS OF RIPPLES IN THIN GOLD FILM ................................... 69
6.4 DELAMINATION OF SILVER ................................................................ 72
6.5 CONCLUSIONS ................................................................................... 73
7 MODEL OF RIPPLE FORMATION IN THIN CHROMIUM FILM
UNDER NANOSECOND LASER IRRADIATION ................................... 74
7.1 MODEL OF PERIODICAL CHROMIUM FRACTURE................................. 74
7.2 MODEL OF RIPPLE FORMATION .......................................................... 75
7.2.1 Ridge formation and Plateau-Rayleigh instability ........................ 77
7.2.2 Steady growth of regular ripples................................................... 81
7.2.3 Marangoni convection velocity for liquid chromium ................... 84
7.3 CONCLUSIONS ................................................................................... 86
LIST OF CONCLUSIONS ............................................................................ 88
SUMMARY ..................................................................................................... 89
REFERENCES ................................................................................................ 90
6ACKNOWLEDGMENTS
The work was supported by the Lithuanian State Science and Studies
Foundation under projects No B21/2006 and B31/2008.
I am very grateful to my scientific supervisor Dr. G. Raiukaitis for
endless patience and huge support.
Thanks to Dr. M. Brikas for introduction to my supervisor Dr. G.
Raiukaitis.
Thanks to my colleague Dr. K. Regelskis for valuable discussions.
Thanks to my colleagues B. Voisiat, E. Stankeviius, P. Geys, R.
Trusovas, G. Darianovas, V. Kuikas, S. Grubinskas, S. Indrišinas and Dr.
M. Maciuleviius for friendly atmosphere in the laboratory.
I express my thanks to Dr. A. Selskis from the Institute of Chemistry of
Center for Physical Sciences and Technology, Vilnius for technical assistance
and Prof. E. Ohmura from Osaka University for fruitful discussions.
I would also like to thank my family and friends for support during never-
ending studies.
7LIST OF ABBREVIATIONS
List of acronyms
-6µm Micrometer (10 m)
3D Three dimensional
AFM Atomic force microscopy
CW Continuous wave
-15fs Femtosecond (10 s)
HAZ Heat affected zone
IR Infrared
ISI Institute of Scientific Information
LIPSS Laser induced periodical surface structures
Nd:YAG Neodymium-doped yttrium aluminum garnet (Nd:Y Al O ) 3 5 12
-9nm Nanometer (10 m)
-9ns Nanosecond (10 s)
PC Pockels cell
-12ps Picosecond (10 s)
SEM Scanning electron microscope
TTM Two temperature model
UV Ultraviolet
WoS Web of Science
List of symbols
A Absorptivity, [-]
A Hamaker constant, [J] H
-1C Specific heat capacity, [J·kg ] p
-1d Ablation depth per pulse (ablation rate), [m·pulse ]
D Diameter of ablated (modified) area, [m]
D Depth of the Heat affected zone, [m] haz
E Young’s modulus, [Pa]
8E Laser pulse energy, [J] p
f Focal length, [m]
-2F Laser fluence, [J·m ]
-2F Peak laser fluence, [J·m ] 0
f Pulse repetition rate, [Hz] Rep
h Film thickness, [m]
-2I Laser intensity, [W·m ]
k Extinction coefficient (imaginary part of refractive index), [-]
-1L Heat of fusion, [J·kg ] m
-1L Heat of vaporization, [J·kg ] v
m Diffraction order, [Integer]
-1M Standard atomic weight, [kg·mol ]
2M Beam quality factor, [-]
Ma Marangoni number, [-]
ñ Refractive index (complex number), [-]
N Number of pulses per spot, [-]
n Refractive index (real part of refractive index), [-]
p Pressure, [Pa]
R Reflectivity, [-]
* -1 -1R Gas constant, [J·mol ·K ]
T Temperature, [K]
t Time, [s]
T Melting point, [K] m
T Boiling point, [K] v
T Transmittance, [-]
-1u Marangoni speed, [m·s ]
3 -1V Atomic or molar volume, [m ·mol ]
-1v Scanning speed, [m·s ]
w Gaussian beam radius, [m] 0
x, y, z Spatial coordinates, [m]
9List of Greek symbols
-1 Absorption coefficient, [m ]
-2 Thermal diffusivity, [s· m ] diff
-1 Effective absorption coefficient, [m ] eff
-1 Thermal expansion coefficient, [K ]
-1 Surface tension of liquid, [N·m ]
T Temperature difference, [K]
x Shift between pulses, [m]
Strain, [-]
-2 Dynamic viscosity, [N·s·m ]
-1 -1 Thermal conductivity, [W·K ·m ]
Ripple period, [m]
Wavelength of laser radiation, [m]
Poisson ratio, [-]
-3
Density, [kg·m ]
Stress, [Pa]

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