Laser Ablation for Chemical Analysis: 50 Years Rick Russo Lawrence Berkeley National Laboratory Applied Spectra, Inc 2012 Laser Damage Boulder, CA September 25, 2012
Laser Ablation for Chemical Analysis: 50 Years Benefits of Laser Damage!
Laser Ablation - Chemical Analysis F. Brech and L. Cross, Optical Microemission Stimulated by a Ruby Laser, Applied Spectroscopy 16, p59 (1962)"
Laser Ablation? 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 - Chemical Analysis Laser Ablation LIBS - LAMIS Plasma ICP (MS or OES) Particles
Laser transforms tiny portion of solid sample into aerosol for direct chemical analysis (mass or optical detection) Real time analysis Every element on the periodic chart Elemental, isotopic and molecular classification Organic vs inorganic Laser Ablation - Chemical Analysis 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
Measurement Laser Ablation High power laser beam explodes portion of sample! 4 Laser Ablation Nuclear Explosion 1 2 Irradiance Theory: Non-linear processes Laser material interaction Laser-plasma interaction Plasma-sample interaction Vapor phase processes Vapor phase chemistry 3
Plasma Temperature (K) Electron Number Density (cm -3 ) Non-linear Nd: YAG Laser, =266nm, t p =3ns, t d =30ns, t g =20ns 10 5 5X10 4 Electron num ber density Plasma Temperature T=A 2 0.25 3X10 19 2X10 19 2X10 4 T=A 1 0.54 n e =B 1 0.24 n e =B 2 1.45 10 19 5X10 18 10 4 10 9 3X10 9 10 10 2X10 10 7X10 10 Irradiance (W/cm 2 )
C rater depth (m m) Craters, Pits, Laser Targets I=15 GW/cm 2 10 I=21 GW/cm 2 1 10 9 10 10 10 11 Laser Power D ensity (W /cm 2 )
Pump and Probe mirror 800 nm, 266nm photodiode/oscilloscope lens beam splitter delay stage beam splitter fs laser CCD lens camera filter target 400 nm BBO double crystal Computer & Electronics
Electron and Mass Plasmas Air plasma Two different plasmas 0 ps 50 ps 150 ps Mass Plasma Air plasma Disappears in vacuum Occurs at 0 ps Mass plasma Exists in vacuum appears at 400 ps More dense 500 ps 1200 ps (pulse energy -- 7.5mJ; pulse length -- 35ps; spot size -- 100mm)
Shock Waves and Particles Sample Surface 500 mm Laser 5 ns 68 ns 200 ns Shock wave propagates in ns Larger particles are ejected after 0.4 ms 400 ns 1.3 ms 20 ms
Peak intensity of spectral line (a.u.) Intensity ( Arb. unit ) Laser Induced Plasmas 15000 10ns delay 10000 30ns delay 5000 50ns delay Nanosecond Femtosecond 150ns delay 0 284 285 286 287 288 289 290 291 292 293 Wavelength (nm) 35000 30000 ns laser fs laser 25000 20000 15000 10000 5000 0 0 100 200 300 400 500 time (ns)
Fundamental Processes Process simulation based on time-resolved measurements of plasma plume 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)
LA-ICP-MS Pulsed Laser LA-ICP-MS: Direct solid sampling Eliminates sample preparation Depth profiling, inclusion, & spatially resolved analysis Rapid & high throughput Gas J100 (+) fs LA-ICP-MS
ns fs ICPS mm Laser Ablated Particles ns-n1711 Al base alloy fs-n1711 Al base alloy 25 20 ns-n1711 fs-n1711 15 10 5 0-5 -10-15 -20-25 0 10 20 30 40 50 60 70 80 90 100 mm 10 10 10 9 66Zn-ns-1u 66Zn-fs-1u 10 8 10 7 10 6 10 5 10 4 0 50 100 150 200 250 300 350 400 450 Time (sec) Particle size and chemistry depends on laser parameters! Nanoparticles
Integrated counts per second (ICPS) Integrated counts per second (ICPS) Integrated counts per second (ICPS) Rapid Analysis of Bulk Samples 10 10 27 Al (N612) 27 Al (Granite) 10 9 10 8 10 7 10 6 10 5 10 4 0 50 100 150 200 250 300 350 400 10 7 Time (sec) 10 7 90 Zr (N612) 88 Sr (N612) 90 Zr (Granite) 88 Sr (Granite) 10 6 10 6 10 5 10 5 10 4 10 4 10 3 10 3 10 2 10 2 10 1 0 50 100 150 200 250 300 350 400 Time (s) 10 1 0 50 100 150 200 250 300 350 400 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. Time (s)
LIBS LIBS = Laser Induced Breakdown Spectroscopy Optical emission from the plasma every element in the sample emits light at a characteristic wavelength when heated to emission fireworks! Sample RT100 LIBS/LAMIS
Curiosity NASA Mars Rover ChemCam (LIBS): 30 elements at once Three spectrometers Analysis time 1-3 min Standoff range 2-9 m
Classification and Discrimination Analysis Products Toxins Cancer Everything has a unique elemental fingerprint a chemical Barcode
Forensics
Classification plants soils
Al(II) 281.62 nm CuO emission Mg (I) 285.21 nm Mg (II) 280.23 nm 3500 3000 Mn (II) 279.83 nm Mg (II) 279.55 nm Mg (II) 279.10 nm Intensity (a. u.) Emission Intensity LIBS LAMIS 12000 Sample:CeO 2 10000 NIST Al alloy Delay time: 0.5 ms Gate width: 0.5 ms 1064 nm Nd:YAG laser 8000 6000 2500 2000 1500 4000 605 606 607 608 609 610 611 612 613 614 615 8000 7000 Wavelength (nm) Sample CuO 1000 6000 500 5000 0 279 280 281 282 283 284 285 286 Wavelength (nm) 4000 3000 Emission spectrum for Elements 2000 603 604 605 606 607 608 609 610 Wavelength (nm) Emission Spectra for Isotopes LAMIS: Laser Ablation Molecular Isotopic Spectroscopy
Emission intensity LIBS LAMIS B ion emission B atom emission BO molecule emission (A-X) BO molecule emission (B-X) 10 6 10 5 10 4 10 3 Atoms/ions form early in plasma Molecules form later in time as plasma cools 10 2 10 1 10 0 0.1 1 10 100 Time (ms)
Emission Intensity Emission Intensity Atomic vs Molecular Spectra D = 2.5 pm D = 730 pm 8 11 B 10 B 9500 9000 8500 8000 10 B 20.24% Natural abundance 19.9% (18.9-20.3) 11 B 10 B Experiment Fitting 7500 7000 4 6500 6000 5500 0 208.945 208.950 208.955 208.960 208.965 Wavelength (nm) Boron Atomic Emission (low pressure) 5000 254.5 255.0 255.5 256.0 256.5 257.0 257.5 258.0 258.5 259.0 Wavelength B-O Molecular Emission (atm pressure) Atomic isotopic shift not resolved at atm pressure!
LAMIS Intensity (arb. unit) Calculated 11 B Concentration Isotope Abundance Ratio Calibration 180 160 140 120 100 80 60 180 160 140 120 100 80 60 180 160 140 120 100 80 60 180 160 140 120 100 80 60 180 160 140 120 100 80 60 40 10 B 0.99 11 B 0.01 O 10 B 0.8 11 B 0.2 O 10 B 0.05 11 B 0.95 O 579 580 581 582 583 584 Wavelength (nm) 10 B 0.52 11 B 0.48 O 10 B 0.2 11 B 0.8 O 100 10/11 Boron ratio 80 60 40 20 0 0 20 40 60 80 100 Standard 11 B Concentration Quantitative analysis using Chemometrics Atmospheric pressure single laser pulse
WO emission Emission Intensity Other Elements/Isotopes 12000 Sample:CeO 2 10000 8000 6000 Ce-O Emission 4000 605 606 607 608 609 610 611 612 613 614 615 22000 Wavelength (nm) Sample W 21000 20000 19000 18000 W-O emission 17000 480.0 480.5 481.0 481.5 482.0 482.5 483.0 483.5 484.0 Wavelength (nm)
Nanometer Spatial Ablation and Analysis LIBS system Near-field optics Beam size (D) ~ aperture size (a<< ) in near field Near-field Gap distance (d1) ~ aperture size (a)
Depth (nm) Near-field Laser Ablation of Si 400 nm, 100 fs Single pulse Smallest features 0.5 0.0-0.5-1.0-100 -75-50 -25 0 25 50 75 100 x-axis (nm) FWHM: 27 nm Depth: 1.2 nm Ablated mass 2 attograms or 5 x10 4 atoms Resolution of ~λ/13
Femtosecond Far-Field LIBS Height (nm) Height (nm) Single-pulse ablation in air Spectral emission AFM surface map 200 Surface Profile 100 Na 0-100 450 nm Wavelength (nm) -200-2 0 2 X (μm) Minimal detectable Na mass : 220 10-18 gr
Normalized Integrated Intensity (a.u.) LIBS Nanometer depth profiling Sample Depth resolution Laser Induced plasma Spectroscopy 0 10 20 30 40 50 H O SEI layer (~50nm) Li HOPG basal plane P Model System: Highly Oriented Pyrolytic Graphite (HOPG) electrode at 0.7V vs. Li/Li + in LiPF 6 /EC-DEC (1:2) electrolyte F C 7nm depth resolution! 0 10 20 30 40 50 # laser pulses C 2
Summary 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) LAMIS
Thank You 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) Funding: Department of Energy Defense Threat Reduction Agency NASA SBIR