Time evolution of the electron density and temperature in laser-produced plasmas from YBa2Cu3O7

Abstract

Abstract. Laser radiation at 1.06 µm from a pulsed Nd:YAG laser was focused onto a multielement YBa 2 Cu 3 O 7 target in vacuum and the plasma thus generated was studied using time-resolved spectroscopic techniques. Line broadening of the Ba I emission line at 553.5 nm was monitored as a function of time elapsed after the incidence of a laser pulse on the target. Measured line profiles of barium species were used to infer the electron density and temperature, and the time evolution of these important plasma parameters has been worked out.PACS: 52.50Jm; 52.70 kz Pulsed laser ablation has become a very successful method for the deposition of high-quality superconducting YBa 2 Cu 3 O 7 thin films [1][2][3][4]. Because of this and other technological applications, considerable efforts have been made to understand the dynamics of the laser-ablated material. The ablation process is accompanied by formation of a bright plasma plume expanding from the target. The laser-induced plasma is characterized by plasma temperature, density, particle expansion velocities, particle charge states and internal fields due to charge separation during plasma expansion.Optical methods are the most suitable for performing the deposition process control. However, the solution of the processing control problems depends on understanding the basic physics and chemistry associated with laser-target and particle-particle interaction occurring within the laserinduced plasma plume. The emission spectra obtained from a multicomponent YBa 2 Cu 3 O 7 target show numerous emission lines and bands corresponding to neutral particles, ions and diatomic molecules. The dynamics of the laser-ablated YBa 2 Cu 3 O 7 plume has been studied by various techniques such as optical emission spectroscopy [5][6][7][8][9], streak photography [10,11], optical absorption spectroscopy [12][13][14], * Present Address: Department of Physics, Sree Narayana College, Punalur 691 305, India * * E-mail: root@cochin.ernet.in optical time-of-flight measurements in the nanosecond timescale range [15][16][17][18][19], interferometry [20], and laser-induced fluorescence [21]. However, most of them have been aimed at identification of ablated species and on the evaluation of their velocity distributions. In our previous experiment it was found that the temporal distributions of various ionic, atomic and molecular species were strongly influenced by the spatial position of the plume from the target and the laser fluence used [15].Besides the identification of the different species generated, most of the time-resolved measurements have focused on dynamics of ejected species from the surface. In the published studies, however, little attention has been paid to the fundamental parameters of the plasma such as electron temperature (T e ), electron density (n e ), and their evolution after the initiation of the laser plasma. Several diagnostic techniques are employed in the determination of n e and T e , including Thomson scattering [22], emission spectroscopy [23][24][25], Langmuir prob...

Spatial and temporal evolution of argon sparks

“…The temporal evolution of electron temperature and electron density is of prime importance, since many kinetic reaction rates depend directly or indirectly on these parameters. 25 The variation in temperature and density as a function of time is given in Fig. 8 and 9 for two axial points in the spark.…”

“…[21][22][23] Thomson scattering is probably the most direct and least theory dependent, whereas spectroscopy is the simplest as far as instrumentation is concerned. Electron excitation temperatures and electron densities are estimated by using optical emission spectroscopy and are reported for laser-produced plasmas with solid targets 24,25 and gases such as air 26 and hydrogen. 27 Cadwell and Huwel 28 measured the temperature and density of laser-created argon sparks at delay times between 60 and 140 s after spark formation.…”

CN emission spectroscopy study of carbon plasma in nitrogen environment

“…In pulsed laser deposition, in presence of an inert or chemically active gas, the optical emission spectroscopy is widely used to diagnose the plasma plume [2 -5], and it is suitable for performing the deposition process control. The solution of the processing control problem depends on the understanding of the basic physics and chemistry associated with laser-target and particle -particle interaction inside the laser induced plasma plume [6].…”

Characterization of ablated species in laser-induced plasma plume

“…Many studies on the electron density in the plasma plume have been performed, using techniques such as optical emission spectroscopy, 19,20 the Langmuir probe, 21,22 interferometry, 23,24 and optical transmissivity. 25 The emission spectroscopy has been widely used because of its noncontact nature of probing and the information attainable over a wide spectral range.…”

“…The electron density has been estimated from the Stark broadening of emission lines in the case of the laser ablation under low pressure conditions. 19,20 Under high pressure conditions, however, the emission lines with a self-reversed structure are often observed, where the electron density cannot be evaluated simply from the width of the spectral line. The appearance of the selfreversed structure is due not only to a high optical thickness of the plume but also to different spatial distributions for the atomic population densities of the two levels involved in the transition.…”