Lawrence Berkeley National Laboratory

Applied Spectra, Inc

2012 Laser Damage Boulder, CA

September 25, 2012

Rick Russo

Laser Ablation for Chemical Analysis: 50 Years

Laser Ablation for Chemical Analysis: 50 Years

Benefits of Laser Damage!

F. Brech and L. Cross, Optical

Microemission Stimulated by a

Ruby Laser, Applied Spectroscopy

16, p59 (1962)"

Laser Ablation - Chemical Analysis

Laser ablation is the process of removing material from a solid (or occasionally liquid)

surface by irradiating it with a laser beam. At low laser flux, the material is heated by the

absorbed laser energy and evaporates or sublimates. At high laser flux, the material is

typically converted to a plasma. Usually, laser ablation refers to removing material with a

pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the

laser intensity is high enough.

Wikipedia (2011)

Laser Ablation?

Laser Ablation - Chemical Analysis

Plasma

Particles ICP (MS or OES)

LIBS - LAMIS

Laser Ablation

• Real time analysis

• Every element on the periodic chart

• Elemental, isotopic and molecular classification

• Organic vs inorganic

• No sample preparation, consumable or waste

• Nominal sample quantity (mg – ag)

• Spatial and depth resolution (nm to mm)

• Qualitative, quantitative and/or classification

• Laboratory, field, standoff applications

Laser transforms tiny portion of solid sample into aerosol for direct

chemical analysis (mass or optical detection)

Laser Ablation - Chemical Analysis

High power laser beam explodes ‘portion of’ sample!

Nuclear Explosion

Laser Ablation

Theory:

Non-linear processes

Laser material interaction

Laser-plasma interaction

Plasma-sample interaction

Vapor phase processes

Vapor phase chemistry

2

1

3

4

Irradiance

Mea

sure

men

t

Laser Ablation

109

1010

104

105

Nd: YAG Laser, =266nm, tp=3ns, t

d=30ns, t

g=20ns

2X104

ne=B

2

1.45

ne=B

1

0.24

5X104

2X1010

3X109

7X1010

Irradiance (W/cm2)

P

las

ma

Te

mp

era

ture

(K

)

Plasma Temperature

1019

3X1019

T=A2

0.25

T=A1

0.54

5X1018

2X1019

Ele

ctr

on

Nu

mb

er

De

ns

ity

(c

m-3

)

Electron number density

Non-linear

109

101 0

101 1

1

10

Cra

ter

de

pth

(m

m)

Laser Power Density (W /cm2)

I=15 GW/cm2

I=21 GW/cm2

Craters, Pits, Laser Targets

Computer

&

Electronics

fs laser

delay stage

photodiode/oscilloscope

mirror

filter

lens

camera

beam splitter

lens

CCD

beam splitter

target BBO double

crystal

400 nm

800 nm, 266nm

Pump and Probe

(pulse energy -- 7.5mJ; pulse length -- 35ps; spot size -- 100mm)

• Two different plasmas

•Air plasma

Disappears in vacuum

Occurs at 0 ps

•Mass plasma

Exists in vacuum

appears at 400 ps

More dense

0 ps 50 ps 150 ps

500 ps 1200 ps

Air plasma

Mass Plasma

Electron and Mass Plasmas

5 ns 68 ns 200 ns

400 ns

500 mm

Shock wave

propagates in ns

Larger particles

are ejected after

0.4 ms

1.3 ms 20 ms

Sa

mp

le Su

rface

Laser

Shock Waves and Particles

284 285 286 287 288 289 290 291 292 293

0

5000

10000

15000

150ns delay

50ns delay

30ns delay

10ns delay

Inte

ns

ity

( A

rb.

un

it )

Wavelength (nm)

Nanosecond Femtosecond

Laser Induced Plasmas

0 100 200 300 400 500

0

5000

10000

15000

20000

25000

30000

35000

Pe

ak in

ten

sity o

f sp

ectr

al lin

e (

a.u

.)

time (ns)

ns laser

fs laser

• ISW = internal shockwave

ESW = external shockwave

• Laser-sample interaction

(~few fs to ~few ns)

• Vapor plume expansion

(~few ns to ~1ms)

• Radiative cooling

(~1ms to ~100ms)

• Vapor plume condensation

(~100ms to ~100ms)

Process simulation based on time-resolved measurements of plasma plume

Fundamental Processes

Pulsed Laser

Gas

LA-ICP-MS

J100 (+) fs LA-ICP-MS

• LA-ICP-MS:

Direct solid sampling

Eliminates sample preparation

Depth profiling, inclusion, & spatially resolved analysis

Rapid & high throughput

fs-N1711 Al base alloy ns-N1711 Al base alloy

0 10 20 30 40 50 60 70 80 90 100

-25

-20

-15

-10

-5

0

5

10

15

20

25

mm

mm

ns-N1711

fs-N1711

0 50 100 150 200 250 300 350 400 450

104

105

106

107

108

109

1010

ICP

S

Time (sec)

66Zn-ns-1u

66Zn-fs-1u

ns fs

Particle size and chemistry depends

on laser parameters! Nanoparticles

Laser Ablated Particles

0 50 100 150 200 250 300 350 400

101

102

103

104

105

106

107

Inte

gra

ted

co

un

ts p

er

se

co

nd

(IC

PS

)

Time (s)

88

Sr (N612)

88

Sr (Granite)

0 50 100 150 200 250 300 350 400

104

105

106

107

108

109

1010

Inte

gra

ted

co

un

ts p

er

se

co

nd

(IC

PS

)

Time (sec)

27

Al (N612)

27

Al (Granite)

0 50 100 150 200 250 300 350 400

101

102

103

104

105

106

107

Inte

gra

ted

co

un

ts p

er

se

co

nd

(IC

PS

)

Time (s)

90

Zr (N612)

90

Zr (Granite)

NIST 612 and granite at 6um spot, 40mm/sec and 20KHz. The signal response can be used to provide ‘level’ of

inhomogeneity in the sample. Integrated signal provides bulk analysis. More scan time leads to bulk properties from

inhomogeneous samples.

Rapid Analysis of Bulk Samples

Sample

RT100 LIBS/LAMIS

Optical emission from the plasma – every element in the sample emits light at a characteristic wavelength when heated to emission – fireworks!

LIBS = Laser Induced Breakdown Spectroscopy

LIBS

ChemCam (LIBS):

• 30 elements at once

• Three spectrometers

• Analysis time 1-3 min

• Standoff range 2-9 m

Curiosity

NASA Mars Rover

Everything has a unique elemental fingerprint – a chemical “Barcode”

Classification and Discrimination Analysis

Cancer Toxins Products

Forensics

plants soils

Classification

603 604 605 606 607 608 609 610

2000

3000

4000

5000

6000

7000

8000

Cu

O e

mis

sio

n

Wavelength (nm)

Sample CuO

279 280 281 282 283 284 285 286

0

500

1000

1500

2000

2500

3000

3500

Mg (

I) 2

85.2

1 n

m

Al(

II)

281.6

2 n

m

Mg (

II)

280.2

3 n

m

Mn (

II)

279.8

3 n

mM

g (

II)

279.5

5 n

m

Inte

nsity (

a.

u.)

Wavelength (nm)

NIST Al alloy

Delay time: 0.5 ms

Gate width: 0.5 ms

1064 nm Nd:YAG laser

Mg (

II)

279.1

0 n

m

Emission Spectra for Isotopes Emission spectrum for Elements

LIBS LAMIS

605 606 607 608 609 610 611 612 613 614 615

4000

6000

8000

10000

12000

Sample:CeO2

Em

issio

n In

ten

sity

Wavelength (nm)

LAMIS: Laser Ablation Molecular Isotopic Spectroscopy

0.1 1 10 100

100

101

102

103

104

105

106

Em

issio

n in

ten

sit

y

Time (ms)

B ion emission

B atom emission

BO molecule emission (A-X)

BO molecule emission (B-X)

Molecules form

later in time

as plasma cools

LIBS LAMIS

Atoms/ions form

early in plasma

208.945 208.950 208.955 208.960 208.965

0

4

8

10B

11B

Em

issio

n Inte

nsity

Wavelength (nm)

B-O Molecular Emission (atm pressure) Boron Atomic Emission (low pressure)

D = 2.5 pm D = 730 pm

Atomic isotopic shift not resolved at atm pressure!

254.5 255.0 255.5 256.0 256.5 257.0 257.5 258.0 258.5 259.0

5000

5500

6000

6500

7000

7500

8000

8500

9000

9500

10B 20.24%

Natural abundance 19.9% (18.9-20.3)

Em

issio

n In

ten

sity

Wavelength

Experiment

Fitting

10B

11B

Atomic vs Molecular Spectra

579 580 581 582 583 584

406080

100120140160180

LA

MIS

In

ten

sity (

arb

. u

nit)

10B

0.05

11B

0.95O

10B

0.8

11B

0.2O

10B

0.99

11B

0.01O

Wavelength (nm)

6080

100120140160180

10B

0.2

11B

0.8O

6080

100120140160180

10B

0.52

11B

0.48O

6080

100120140160180

6080

100120140160180

0 20 40 60 80 100

0

20

40

60

80

100

Ca

lcu

late

d 1

1B

Co

nce

ntr

atio

n

Standard 11

B Concentration

Quantitative analysis using Chemometrics

Atmospheric pressure – single laser pulse

10/11 Boron ratio

Isotope Abundance Ratio Calibration

Ce-O Emission

605 606 607 608 609 610 611 612 613 614 615

4000

6000

8000

10000

12000

Sample:CeO2

Em

issio

n In

ten

sity

Wavelength (nm)

W-O emission 480.0 480.5 481.0 481.5 482.0 482.5 483.0 483.5 484.0

17000

18000

19000

20000

21000

22000

WO

em

issio

n

Wavelength (nm)

Sample W

Other Elements/Isotopes

LIBS system

Beam size (D) ~ aperture size (a<< ) in near field

Near-field Gap distance (d1) ~ aperture size (a)

Near-field optics

Nanometer Spatial Ablation and Analysis

FWHM: 27 nm Depth: 1.2 nm

Resolution of ~λ/13

400 nm, 100 fs

Single pulse

Smallest features

-100 -75 -50 -25 0 25 50 75 100

-1.0

-0.5

0.0

0.5

Dep

th (

nm

)

x-axis (nm)

Ablated mass 2 attograms or

5 x104 atoms

Near-field Laser Ablation of Si

Femtosecond Far-Field LIBS

Minimal detectable Na mass : 220·10-18 gr

Heig

ht

(nm

)

AFM surface map Spectral emission

-2 0 2-200

-100

0

100

200

Single-pulse ablation in air

450 nm

Surface Profile

He

igh

t (n

m)

X (μm) Wavelength (nm)

Na

LIBS Nanometer depth profiling

0 10 20 30 40 50

0 10 20 30 40 50

C2

C

F

P

Li

O

H

Laser Induced plasma Spectroscopy

# laser pulses

No

rmal

ize

d In

tegr

ated

Inte

nsi

ty (

a.u

.)

SEI layer (~50nm)

HOPG basal plane

Depth resolution

Model System: Highly Oriented Pyrolytic Graphite (HOPG) electrode at 0.7V vs. Li/Li+ in LiPF6/EC-DEC (1:2) electrolyte

Sample

7nm depth resolution!

Laser Ablation: Analytical Spectroscopy

• Rapid, real-time analysis (no sample preparation)

• Elemental, isotopic, classification

• Sub-micron (nanometer) depth and spatial analysis

• Sensitivity – attogram absolute mass detection

• Monitor of Laser Damage (external and internal)

Summary

LAMIS

Co Authors:

Jhanis J. Gonzalez, Vassilia Zormpa, Inhee Choi, Javier Ruiz.

Lawrence Berkeley National Laboratory (USA)

Alexander A. Bolshakov, Jong H. Yoo

Applied Spectra, Inc. (USA)

Thank You

Funding:

Department of Energy

Defense Threat Reduction Agency

NASA

SBIR