Magnetic field effect on laser-induced breakdown spectroscopy and surface modifications of germanium at various fluences

Abstract

The effect of the transverse magnetic field on laser-induced breakdown spectroscopy and surface modifications of germanium (Ge) has been investigated at various fluences. Ge targets were exposed to Nd: YAG laser pulses (1064 nm, 10 ns, 1 Hz) at different fluences ranging from 3 to 25.6 J/cm2 to generate Ge plasma under argon environment at a pressure of 50 Torr. The magnetic field of strength 0.45 Tesla perpendicular to the direction of plasma expansion was employed by using two permanent magnets. The emission spectra of laser-induced Ge plasma was detected by the laser-induced breakdown spectroscopy system. The electron temperature and number density of Ge plasma are evaluated by using the Boltzmann plot and stark broadening methods, respectively. The variations in emission intensity, electron temperature (Te), and number density (ne) of Germanium plasma are explored at various fluences, with and without employment of the magnetic field. It is observed that the magnetic field is responsible for significant enhancement of both excitation temperature and number density at all fluences. It is revealed that an excitation temperature increases from Te,max,without B = 16,190 to Te,max,with B = 20,123 K. Similarly, the two times enhancement in the electron density is observed from ne,max,without B = 2 × 1018 to ne,max,with B = 4 × 1018 cm−3. The overall enhancement in Ge plasma parameters in the presence of the magnetic field is attributed to the Joule heating effect and adiabatic compression. With increasing fluence both plasma parameters increase and achieve their maxima at a fluence of 12.8 J/cm2 and then decrease. In order to correlate the plasma parameters with surface modification, scanning electron microscope analysis of irradiated Ge was performed. Droplets and cones are formed for both cases. However, the growth of ridges and distinctness of features is more pronounced in case of the absence of the magnetic field; whereas surface structures become more diffusive in the presence of the magnetic field.

Effect of magnetic field on the laterally colliding plasma plumes

“…Effect of magnetic field on laser produced single plasma is well studied. [1][2][3]6] In the present study we focus on the study of interaction zone formed by colliding plasmas in presence of external magnetic field. Figure 2(b) represents time integrated images of lateral interactions of two spatially separated plasma plumes in absence and presence of 1000 Gauss magnetic field, respectively, for time delays 100 to 600 ns in vacuum.…”

“…Collision of plasma plumes is an important phenomenon in many laboratory plasma and applications such as plasma confinement, inertial confinement fusion (ICF), laboratory studies of plasma of astrophysical importance, generation of nanoparticles and ion-sources etc. [1][2][3][4][5][6] Expansion of laser produced plasma in the presence of an external magnetic field has been studied experimentally under different conditions and has been illustrated in recent works. [1,[7][8][9][10] Colliding plasma with different targets, laser parameters, ambient and ablation geometries have been reported by several authors.…”

Surface Structuring and Thin Film Coating through Additive Concept Using Laser Induced Plasma of Mg Alloy: A Comparison between the Presence and Absence of Transverse Magnetic Field (TMF)

“…The emission intensity value is higher in Ar, moderate in Ne, and lowest in He. It has been reported by several research groups that this decrease can be attributed to the combination of deceleration and enhanced radiation recombination [15,[21][22][23][24][25]. The decrease in spectral intensity is due to a decrease in the lifetime of upper states attributed to strong magnetic confinement effects [23].…”

“…It has been reported by several research groups that this decrease can be attributed to the combination of deceleration and enhanced radiation recombination [15,[21][22][23][24][25]. The decrease in spectral intensity is due to a decrease in the lifetime of upper states attributed to strong magnetic confinement effects [23]. When TMF confines the plasma and restricts its free expansion, the lifetime for recombination is significantly decreased.…”

“…To determine the T exc of Mg plasma, the Boltzmann plot method was employed [23,28]. The Laser Induced Plasma (LIP) is assumed to be in Local Thermodynamic Equilibrium (LTE).…”