Laser Ablation for Chemical Analysis: 50 Years. Rick Russo Laser Damage Boulder, CA September 25, 2012

Transcription

1 Laser Ablation for Chemical Analysis: 50 Years Rick Russo Lawrence Berkeley National Laboratory Applied Spectra, Inc 2012 Laser Damage Boulder, CA September 25, 2012

2 Laser Ablation for Chemical Analysis: 50 Years Benefits of Laser Damage!

3 Laser Ablation - Chemical Analysis F. Brech and L. Cross, Optical Microemission Stimulated by a Ruby Laser, Applied Spectroscopy 16, p59 (1962)"

4 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)

5 Laser Ablation - Chemical Analysis Laser Ablation LIBS - LAMIS Plasma ICP (MS or OES) Particles

6 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

7 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

8 Plasma Temperature (K) Electron Number Density (cm -3 ) Non-linear Nd: YAG Laser, =266nm, t p =3ns, t d =30ns, t g =20ns X10 4 Electron num ber density Plasma Temperature T=A X X X10 4 T=A n e =B n e =B X X X X10 10 Irradiance (W/cm 2 )

9 C rater depth (m m) Craters, Pits, Laser Targets I=15 GW/cm 2 10 I=21 GW/cm Laser Power D ensity (W /cm 2 )

10 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

11 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 mJ; pulse length -- 35ps; spot size mm)

12 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

13 Peak intensity of spectral line (a.u.) Intensity ( Arb. unit ) Laser Induced Plasmas ns delay ns delay ns delay Nanosecond Femtosecond 150ns delay Wavelength (nm) ns laser fs laser time (ns)

14 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)

15 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

16 ns fs ICPS mm Laser Ablated Particles ns-n1711 Al base alloy fs-n1711 Al base alloy ns-n1711 fs-n mm Zn-ns-1u 66Zn-fs-1u Time (sec) Particle size and chemistry depends on laser parameters! Nanoparticles

17 Integrated counts per second (ICPS) Integrated counts per second (ICPS) Integrated counts per second (ICPS) Rapid Analysis of Bulk Samples Al (N612) 27 Al (Granite) Time (sec) Zr (N612) 88 Sr (N612) 90 Zr (Granite) 88 Sr (Granite) Time (s) 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)

18 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

19 Curiosity NASA Mars Rover ChemCam (LIBS): 30 elements at once Three spectrometers Analysis time 1-3 min Standoff range 2-9 m

20 Classification and Discrimination Analysis Products Toxins Cancer Everything has a unique elemental fingerprint a chemical Barcode

21 Forensics

22 Classification plants soils

23 Al(II) nm CuO emission Mg (I) nm Mg (II) nm Mn (II) nm Mg (II) nm Mg (II) nm Intensity (a. u.) Emission Intensity LIBS LAMIS Sample:CeO NIST Al alloy Delay time: 0.5 ms Gate width: 0.5 ms 1064 nm Nd:YAG laser Wavelength (nm) Sample CuO Wavelength (nm) Emission spectrum for Elements Wavelength (nm) Emission Spectra for Isotopes LAMIS: Laser Ablation Molecular Isotopic Spectroscopy

24 Emission intensity LIBS LAMIS B ion emission B atom emission BO molecule emission (A-X) BO molecule emission (B-X) Atoms/ions form early in plasma Molecules form later in time as plasma cools Time (ms)

25 Emission Intensity Emission Intensity Atomic vs Molecular Spectra D = 2.5 pm D = 730 pm 8 11 B 10 B B 20.24% Natural abundance 19.9% ( ) 11 B 10 B Experiment Fitting Wavelength (nm) Boron Atomic Emission (low pressure) Wavelength B-O Molecular Emission (atm pressure) Atomic isotopic shift not resolved at atm pressure!

26 LAMIS Intensity (arb. unit) Calculated 11 B Concentration Isotope Abundance Ratio Calibration B B 0.01 O 10 B B 0.2 O 10 B B 0.95 O Wavelength (nm) 10 B B 0.48 O 10 B B 0.8 O /11 Boron ratio Standard 11 B Concentration Quantitative analysis using Chemometrics Atmospheric pressure single laser pulse

27 WO emission Emission Intensity Other Elements/Isotopes Sample:CeO Ce-O Emission Wavelength (nm) Sample W W-O emission Wavelength (nm)

28 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)

29 Depth (nm) Near-field Laser Ablation of Si 400 nm, 100 fs Single pulse Smallest features x-axis (nm) FWHM: 27 nm Depth: 1.2 nm Ablated mass 2 attograms or 5 x10 4 atoms Resolution of ~λ/13

30 Femtosecond Far-Field LIBS Height (nm) Height (nm) Single-pulse ablation in air Spectral emission AFM surface map 200 Surface Profile 100 Na nm Wavelength (nm) X (μm) Minimal detectable Na mass : gr

31 Normalized Integrated Intensity (a.u.) LIBS Nanometer depth profiling Sample Depth resolution Laser Induced plasma Spectroscopy 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! # laser pulses C 2

32 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

33 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