Joint Institute for High Temperatures Russian Academy of Sciences, - - PowerPoint PPT Presentation
Joint Institute for High Temperatures Russian Academy of Sciences, Moscow JIHT of RAS Shock, ablation and formation of nanostructures in metals induced by femtosecond laser S.I. Ashitkov, P.S.Komarov, N.A. Inogamov, V.V. Zhakhovsky, M.B.
JIHT of RAS
Santa Fe, NM, USA, April 21-25, 2014
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Laser matter interaction/ experiment and modeling
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Diagnostics of shock phenomena are performed by measuring a free surface velocity profile of a tested sample. Free surface velocity history In plate impact experiment*.
*G.I. Kanel', V. E. Fortov,S.V. Razorenov Physics-Uspekhi 50, (8) (2007)
Time t, µs Free Surface Velocity ufs, km/s 13 GPa
∆ufs
Armco-iron 2.46 mm
α→ε polymorphic phase transition in iron: (bcc → hcp crystal structure transition) Transition stress ≈13GPa in a microsecond range Reflection of shock compression pulse from the free surface leads to appearance of the tensile stresses inside of the sample causing fracture. Value of spall strength is determined from: 2 /
e fs e S HEL
u U ∆ = ρ σ Splitting of shock wave into elastic precursor (HEL) and plastic compression wave makes it possible to determine the plasticflow stress of the material. 2 / ) ( δ ρ σ + ∆ =
fs S spall
u U
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0.5 1 1.5 2.0 2.5 200 100 200 Time, ps
Position y, µm
Phase shift, rad 100
Amplifier Compressоr Stretcher Oscillator
Probe 300 ps
8 1 1 2 1 4 1 6 1 8 2Sample
CCD
Pump 100 fs
Imaging Spectrometer Acton 2300i Imaging Michelson interferometr
Femtosecond Ti:S laser (Legend, Coherent, USA)
Time t, ps
790 810 770 80 160 240
Probe wavelength, nm Time t, ps
790 810 770 80 160 240
Probe wavelength, nm
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In contrast to multipulse pump–probe methods the single-pulse technique ensures much higherreliability of the measurements and can be used to analyze the reproducibility and statistics
samples. Application of Fourier processing of interference patterns and comparison
and during shock wave arrival ensure measurement of surface displacement with nanometric accuracy.
2D Fourier processing
Spatial-temporal phase distribution
Samples: metallic films, deposited by magnetron spattering onto glass substrates
) , ( t y ϕ ∆
Phase distributions at the rear surface of iron targets of different thicknesses after shock breakout
d1 d2
pump 100 fs chirped probe 300 ps
80 100 120 140 160 180 200
0,5 1
C
Ti:S laser
Glass substrate Metal film Gaussian spot Ø=40 µm Phase shift, rad
200 100 0.5 1 1.5 2 0.5 1 1.5 2 250 200 150 50 100 250 200 150 50 100
Time t, ps Position y, a.u.
Fe, 250 nm Fe, 540 nm
50 100 150 200 250 50 100 150
Displacement, nm Time t, ps
Al
500 nm 1200 nm
Free surface displacement histories
π ϕ λ 4 / ) , ( ) ( ) , ( t y t t y z ∆ = ∆
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50 100 150 200 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4
540 nm
Fe Shot # 8
Free Surface Velocity, km/s Time, ps HEL PSW
Splitting of shock into elastic-plastic two-wave configuration at propagation distance of 540 nm Free surface displacement and velocity history at different stress
Ti:S laser: 100fs, 3 J/cm
50 100 150 200 20 40 60 80 100
Displacement z, nm
Time t, ps
Fe, Shot#8
540 nm
Sample: 99.9 purity iron film 540 nm in thick deposited on glass substrate
50 100 150 200 250 0,0 0,4 0,8 1,2 1,6 2,0
Free Surface Velocity, km/s Time, ps 500 nm 1200 nm Al, 3J/cm2 7.1 km/s
8 GPa 14 GPa
50 100 150 200 0,0 0,5 1,0 1,5 2,0 Fe, 3 J/cm2 250 nm 540 nm Free Surface Velocity, km/s Time, ps
6.4 km/s
HEL HEL 27 GPa 13 GPa
Free surface velocity histories
0,00 0,25 0,50 0,75 1,00 5 6 7 8
US = 5.35 + 1.34 up USE = 6.44 + 1.4 up
US, km/s up, km/s
wave into two-zone elastic-plastic configuration was observed
was detected at stress up to 14 GPa with parameters rise time of 1-2 ps US – up diagrams. Elastic Hugoniout.
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7.5 GPa up to 7.9 GPa
Fe
3.4 GPa up to 3.2 GPa
Al
Theoretical limit Experimental value
)) ( ) ( ( 4 3 V p V
z
− = σ τ
Recorded states in elastic shock waves (points) in aluminum and iron films Maximum shear stress at uniaxial compression:
)) ( ) ( ( 4 3 V p V
z
− = σ τ
0,80 0,85 0,90 0,95 1,00 5 10 15 20 σz - p = 2.4 GPa
τ = 1.8 GPa Bulk: US = 5.35 + 1.34 up Elastic: US = 6.44 + 1.4 up σ, GPa
V/V0
σz - p = 4.3 GPa
τ = 3.2 GPa
Al
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S.I. Ashitkov, et al JETP Lett. 98, 384(2013) J.C.Crowhurst, et al J.Appl. Phys. 115, 113506 (2014) 10
10
10
10 10
1
0,01 0,1 1 10
Al, HEL
Whitley, et al Gupta, et al Ashitkov, et al Garkushin, et al Arvidsson, et al Winey, et al
σHEL, GPa
Distance h, mm
Crowhurst, et al
083 . 2 45 . 1
) ( ) (
− −
+ = h h S h h S
HEL
σ
63 . 0)
(
−
= h h S
HEL
σ
Smith et al Kanel et al Ashitkov et al Crowhurst et al S.I.Ashitkov, et al JETP. Lett. 92, 516 (2010)
J.C.Crowhurst, et al Phys.Rew.Lett. 107, 144302 (2011)
l p x
c G dh d γ σ & 3 4
HEL
− =
p
γ&
(G - shear modulus )
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JIHT of RAS, 2013
Fe, 0.5 µm
Laser, 100 fs t Px
Glass
50 ps
Sample: Fe film on a glass substrate Fe
isn’t realized within 20 ps
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LLNL Livermore, 2013
Fe
is realized within 100 ps
J.C. Crowhurst et al, J.Appl. Phys. 115, 113506 (2014) Fe, >1µm
Laser, 300 ps t Px
Glass
300 ps
Sample: Fe film on a glass substrate
Fe 1.6 µm 1.2 µm 100 ps
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fs fs l spall
u u b c ∆ ∆ − = ) 2 ( 2 1 ρ σ
c u V V
fs 2
/ & & =
S.I.Ashitkov, et al JETP. Lett. 92, 516 (2010) nonlinearity of compressibility
Strain rate
Ideal strength 28 GPa
50 100 150 200 250 50 100 150 0,0 0,5 1,0 1,5
760 nm
Al
1200 nm
Displacement z, nm Time, ps
F=2J/cm
2
∆ufs
Free Surface Velocity, km/s
∆ufs
Free surface velocity histories indicate spallation at a pure elastic uniaxial compression in a picosecond range
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N.A. Inogamov, et al Contr.Plasma Phys. 53, 796 (2013)
(a) - density map(b-e) - atomic order map: solid (green), liquid (red)
Expansion of foam,breaking of membranes, and freezing the remnants of membranes near the transit between foam and continuous metal. Result of long large-scale MD simulation of a sample with dimensions LxLyLz = 500x240x24 nm3 and 172x106 atoms. Laser: 100 fs; F/F abl =1.5 SEM images of ablation crater at a surface of gold sample. Laser: 100 fs; F/Fabl=1.5
15 µm 1.5 µm
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chirped probe 300 ps
80 100 120 140 160 180 200
Glass substrate Al film 760 nm
Ti:S laser
pump 100 fs Gaussian spot Ø=40 µm F0 = 0.9 J/cm2
0.1 0.2 0.3
Phase shift, rad
x, a.u.
Time, ps
120
Temporal spatial phase distribution
80 100 120 140 160 180 5 10 15 20
Displacement z, nm Time t, ps F/ Fa=1.2 F/ Fa=0.9 F/ Fa=0.7 Al
40 nm
Crater 50 µm
Profile of ablation crater Displacement history
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Ablation threshold 0.7 J/cm2
500 1000 1500 2000 2500 3000 4 6 8 10 12 14 16
ρ c 10 5, gcm-2c-1
T, K Tm=933 K
Al
Solid Liquid
45 2.5±0.5 3· 109 3.6 2.16 Liquid (2kK) 250 7.7±0.5 2· 109 6.4 2.71 Solid (300 K) LSpall, nm σSpall,, GPa , s-1 c, km/s ρ, gcc Al
2 / ) (
max min
t t c Lspall − =
Map of local atomic order Frontal and rear surface velocity history
experiment MD
2 / u c
spall
∆ = ρ σ
Frontal surface Rear surface
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ε &
c u fs 2 & & = ε
50 100 150 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4
∆u=0.65km/s
Surface Velocity u, km/s Time t, ps
Rear Surface Al, 760nm Frontal Surface
∆u=1 km/s
F=2.1 J/cm2 F=0.9 J/cm2
Ti:S laser, 100 fs
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Single shot interferometric diagnostics was realized to measure surface displacement history with temporal resolution of 1 ps. Experimentally found that uniaxial shock compression in picosecond range is elastic up to stress
The stressed states in aluminum and iron, very close to the values of ultimate shear and bulk strength were measured and implemented in picosecond range of load duration The α→ε polymorphic phase transition in iron film of 540 nm in thick isn’t realized at a stress of 23 GPa within 20 ps after HEL From the expansion surface history the value of tensile stress of about 2.5 GPa leads to spallation
measured. The results of long large-scale MD simulations of nanostructures formation at metal surface after it’s irradiance of femtosecond laser is well similar to SEM images of ablation crater’s morphology
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