Laser-induced plasma formation during pulsed laser deposition

Aden, Mirko; Kreutz, E. W.; Voss, A.

doi:10.1088/0022-3727/26/10/002

Cited by 65 publications

(23 citation statements)

References 20 publications

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“…The study of material expanding into vacuum or in ambient background gas is an important issue in gas dynamics ͑see Ref. [6][7][8][9] The plume expansion can be investigated either by Monte Carlo ͑MC͒ simulations, [12][13][14][15][16] by hydrodynamic models, 3,[17][18][19][20][21][22][23][24][25] or by a hybrid model ͑combination of both͒. Laser pulses used in PLD have typically a duration of several tens of nanoseconds and an energy fluence of several J / cm 2 .…”

Section: Introductionmentioning

confidence: 99%

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Laser ablation of Cu and plume expansion into 1atm ambient gas

Chen

Bogaerts

2005

Journal of Applied Physics

165

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A one-dimensional gas-dynamic model is presented for the laser ablation of Cu and the expansion of the Cu vapor in a background gas ͑He͒ at 1 atm. The ionization of Cu and He, the inverse bremsstrahlung absorption processes and photoionization process, and the back flux onto the target are considered simultaneously. The binary diffusion, the viscosity, and the thermal conduction including the electron thermal conduction are considered as well. Numerical results show that the consideration of ionization and laser absorption in the plume greatly influences the gas dynamics. The ionization of Cu enables the recondensation at the target surface to happen even during the laser pulse. The ionization degree of Cu and He may change greatly with the location in the plume. For laser irradiances ranging from 2 to 9 ϫ 10 12 W/m 2 , the simulations show that the second-order ionization of Cu competes with the first-order ionization. In the region close to the target surface, the first-order ionization of Cu dominates. In the core of the plasma, the second-order ionization of Cu may dominate over the first-order ionization at laser irradiances higher than 7 ϫ 10 12 W/m 2 . In the mixing layer, the first-order ionization of Cu is always more important than the second-order ionization although the latter increases monotonously with laser irradiance. The ionization of He is only important in the mixing layer. The plume expansion velocity is much larger than that without ionization and laser absorption by the plume. The relative importance of different laser absorption mechanisms may change with time. Close to the surface photoionization and electron-neutral inverse bremsstrahlung are always important. Once the ionization in the plume starts, at later time, electron-ion inverse bremsstrahlung can become more important than photoionization in the plume core until the shock wave front. Unlike in the vacuum case, electron-neutral inverse bremsstrahlung is very strong due to the relatively high number density of neutral atoms in the plume in the presence of a dense ambient gas. A similar laser irradiance threshold is found for the ablation rate and the plasma formation in the plume, which agrees well with the case of nanosecond laser ablation of metals in vacuum.

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Section: Introductionmentioning

confidence: 99%

“…10͒ and for laser ablation. 26,27 Among the hydrodynamic models the pressure is mostly limited till maximum about 100 Pa. 18,[21][22][23][24] The plume expansion into 1-atm background gas was investigated only in Refs. The quality of the deposited film depends critically on the range and profile of the kinetic energy of the ablated plume.…”

Section: Introductionmentioning

confidence: 99%

Laser ablation of Cu and plume expansion into 1atm ambient gas

Chen

Bogaerts

2005

Journal of Applied Physics

165

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“…10͒ and for laser ablation. The plume expansion, which may be strongly influenced by the laser-induced plasma, can be investigated either by Monte Carlo ͑MC͒ simulations, [12][13][14][15][16] by hydrodynamic models, 3, [17][18][19][20][21][22][23][24][25][26][27] or by a hybrid model ͑combination of both͒. When LA is used for solid material analysis, e.g., laser-induced breakdown spectroscopy ͑LIBS͒, 11 or LA as a sample introduction method for an inductively coupled plasma ͑ICP͒, the laser pulses have typically a laser irradiance between 10 8 and 10 9 W/cm 2 and a duration of a few nanoseconds.…”

Section: Introductionmentioning

confidence: 99%

Effect of ambient pressure on laser ablation and plume expansion dynamics: A numerical simulation

Chen

Bleiner

Bogaerts

2006

Journal of Applied Physics

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A comprehensive numerical model is applied to the study of the effect of ambient pressure in laser ablation, more specifically on the copper target heating, melting and vaporization, and the resulting plume expansion in the helium gas, as well as on plasma formation in the plume. Under the laser pulse condition investigated ͓5 ns full width at half maximum ͑FWHM͒ and 10 9 W/cm 2 peak irradiance͔, the calculated results show that the characteristics of the surface temperature and the evaporation depth are very similar even when the ambient pressure varies greatly. The influence of the ambient pressure on the fraction of absorbed laser energy is also small. The maximum ablated material vapor density in the plume is influenced slightly by the different pressures. Before 40 ns, the maximum plume temperature for various ambient pressures is in the order of a few 10 4 K. However, the effect of ambient pressure on the plume length is quite large. A specific calculation for a Gaussian-shaped laser pulse with 6 ns FWHM and 2.76ϫ 10 9 W/cm 2 peak irradiance is made. The calculated evaporation depth agrees well with the experimental data. Therefore, the model can be useful to predict trends in target and plume ͑plasma͒ characteristics, which are difficult to obtain experimentally for various ambient pressures.

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“…A "plasma core" stays in contact with the target surface until the end of the laser pulse. After 200 ns a lumious plasma front can be observed above this core [16]. This plasma front can be characterized with short time spectroscopy and is identified as four different Til-lines between 502 nm and 512 nm.…”

Section: Observation Of Laser-matter-interaction With Short Time Diagmentioning

confidence: 95%

<title>Contribution to the beam plasma material interactions during material processing with TEA CO2 laser radiation</title>

Jaschek¹,

Konrad²,

Mayerhofer³

et al. 1995

SPIE Proceedings

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The TEA-C02-laser (ransverse1y xcited atmospheric pressure) is a tool for the pulsed processing of materials with peak power densities up to 1O" W/cm2 and a FWHM of 70 ns. The interaction between the laser beam, the surface of the work piece and the surrounding atmosphere as well as gas pressure and the formation of an induced plasma influences the response of the target. It was found that depending on the power density and the atmosphere the response can take two forms. (1) No target modification due to optical break through of the atmosphere and therefore shielding of the target (air pressure above 10 mbar, depending on the material).(2) Processing of materials (air pressure below 10 mbar, depending on the material) with melting of metallic surfaces (power density above 0.5 lO W/cm2), hole formation (power density of 5 iO W/cm2) and shock hardening (power density of 3 .5 lO W/cm2). All those phenomena are usually linked with the occurance of laser upported combustion waves (LSC) and laser upported detonation waves (LSD), respectively for which the mechanism is still not completely understood. The present paper shows how short time photography and spatial and temporal resolved spectroscopy can be used to better understand the various processes that occur during laser beam interaction. The spectra of titanium and aluminum are observed and correlated with the modification of the target. If the power density is high enough and the gas pressure above a material and gas composition specific threshold, the plasma radiation shows only spetral lines of the background atmosphere. If the gas pressure is below this threshold, a modification of the target surface (melting, evaporation and solid state transformation) with TEA-C02-laser pulses is possible and the material specific spectra is observed. In some cases spatial and temporal resolved spectroscopy of a plasma allows the calculation of electron temperatures by comparison of two spectral lines.

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Laser-induced plasma formation during pulsed laser deposition

Cited by 65 publications

References 20 publications

Laser ablation of Cu and plume expansion into 1atm ambient gas

Laser ablation of Cu and plume expansion into 1atm ambient gas

Effect of ambient pressure on laser ablation and plume expansion dynamics: A numerical simulation

<title>Contribution to the beam plasma material interactions during material processing with TEA CO2 laser radiation</title>

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