Experimentally constrained multidimensional simulation of laser-generated plasmas and its application to UV nanosecond ablation of Se and Te

Abstract

We carry out simulations of laser plasmas generated during UV nanosecond pulsed laser ablation of the chalcogens selenium (Se) and tellurium (Te), and compare the results to experiments. We take advantage of a 2D-axisymmetric, adaptive Cartesian mesh framework that enables plume simulations out to centimeter distances over tens of microseconds. Our model and computational technique enable comparison to laser-plasma applications where the long-term behavior of the plume is of primary interest, such as pulsed laser synthesis and modification of materials. An effective plasma absorption term is introduced in the model, allowing the simulation to be constrained by experimental time-of-flight kinetic energy distributions. We show that the effective simulation qualitatively captures the key characteristics of the observed laser plasma, including the effect of laser spot size. Predictions of full-scale experimentally-constrained Se and Te plasmas for 4.0 J cm −2 laser fluence and 1.8 mm 2 circular laser spot area show distinct behavior compared to more commonly studied copper (Cu) plumes. The chalcogen plumes have spatial gradients of plasma density that are steeper than those for Cu by up to three orders of magnitude. Their spatial ion distributions have central bulges, in contrast to the edge-only ionization of Cu. For the irradiation conditions explored, the range of plasma temperatures for Se and Te is predicted to be higher than for Cu by more than 0.50 eV.

Deposition Methods for the Integration of Molecularly Imprinted Polymers (MIPs) in Sensor Applications

“…[ 222 ] Different CVD operating conditions are selected based on the material being deposited, with variations regarding the working pressure, vapor characteristics, and substrate heating being just a few parameters that are altered when making this consideration. [ 223 ] Currently the most common variation associated with MIPs is initiated chemical vapor deposition (iCVD), which is a method that is traditionally related to the deposition of dense conformal coatings onto solid substrates. [ 224 ] In essence, this method uses free‐radical polymerization to synthesize thin films across a substrate, where the vaporized constituent components of the polymer (monomer, crosslinker, and initiator) are introduced inside a vacuum chamber containing template‐functionalized substrates.…”

Two-dimensional axisymmetric radiation hydrodynamics model of moderate-intensity nanosecond laser-produced plasmas

“…Up to now, many hydrodynamic models for moderateintensity ns-laser radiation [17][18][19][20][21][22][23][24][25][26][27] have been proposed. However, most of the models still need to be improved in the following three aspects: (a) Adoption of a correct absorption coefficient for electron-neutral inverse Bremsstrahlung.…”

“…(b) It is necessary to calculate the energy level population and charge state distribution in the plasma during laser ablation by using the collisional-radiation (CR) model. Some hydrodynamic models [17,18,21,22,[24][25][26] assumed that LPP is in local thermodynamic equilibrium (LTE) from the beginning of laser ablation to the plasma expansion after the end of the laser pulse. This hypothesis can usually be used to study the expansion process of plasma after the end of laser pulse, but it needs to be carefully considered for the process of laser ablation, especially ultraviolet (UV) laser ablation [28].…”

“…(c) It may be necessary to consider the contribution of the electronic excitation energies of atoms even ions when calculating the internal energy of plasma during laser ablation, that is, the equations of state (EOS) of plasma should be described by using a real gas approximation [31], which includes the excitation, ionization and thermal energies of atoms as well as ions. At present, some models [17,21,26] ignored the contribution of excitation energy to the internal energy of the plasma and only considered the thermal energy and ionization energy. Other models [18,19,24] adopted a more simplified ideal gas approximation, that is, only the contribution of thermal energy was included.…”