Monte Carlo simulation of a sputtering hollow-cathode discharge for laser applications

We report on a kinetic model that computes the electron behaviour in a hollow cathode discharge. It is a part of the PLASIMO toolkit and is based on a Monte-Carlo technique. The model is tested by varying the input parameters and by comparing the output with the output obtained by the freeware Boltzmann equation solver BOLSIG+. The results show that the Monte-Carlo model gives reliable information about the behavior of the electrons in the discharge. The Monte-Carlo module is applied to the case of a hollow cathode discharge for laser applications. Analysis of the output data and its adequateness is done. Future developments of the model are discussed

Monte Carlo simulation of electron kinetics in a hollow cathode discharge

A kinetic model is reported computing the electron behavior in a hollow cathode discharge based on the Monte Carlo technique. It is a part of the PLASIMO modelling toolkit. The model allows the electrons to be closely followed while they travel and undergo collisions in the discharge. The Monte Carlo modulewas applied to the case of a HCD used as an excitation medium of atoms obtained by laser ablation. Results are obtained on the electron energy distribution function and the mean electron energy under typical discharge conditions. The output data and future development of the model and its applications are analyzed and discussed

Pulsed Nd:YAG deposition of nanostructured FeS1-x containing meta-stable phases

Pulzní laserové ozáření sulfidu železitého (FeS) v blízko-IČ oblasti záření ve vakuu umožňuje nekonguerentní ablaci a depozici nanostrukturovaných tenkých vrstev FeS1-x. Depozice byla provedena na nezahřátý substrátu Al, Ta a Cu a tenké filmy byly analyzovány se skenovací (SEM) a transmisní elektronovou mikroskopií (HRTEM) s vysokým rozlišením a elektronovou difrakcí. Morfologicky podobná homogenní, tmavá, kovově vyhlížející adhesní vrstva byla detekována pro všechny depozity (SEM). Při použití HRTEM v souladu s elektronovou difrakcí však bylo zjištěno rozdílné fázové složení na různých substrátech. Na substrátu Ta byla detekována kubická fáze pyritu (FeS2). Kubický pyrit (FeS2) a metastabilní rhomboedrický smytite Fe9S11 byly nalezeny v případě Al substrátu. Kubický pyrit (FeS2), metastabilní rhomboedrický smythite Fe9S11 a metastabilní orthorombický markasit (FeS2m) odhalila HRTEM analýza filmu na Cu substrátu. V případě všech depozitů byla detekovány krystalická nanozrna obklopená amorfní matricí.Pulsed near-IR laser irradiation of ferrous sulfide (FeS) in a vacuum allows a noncongruent ablation and deposition of nanostructured FeS1-x thin films. Deposition has been performed on Al, Ta and Cu unheated substrate and analyzed by scanning (SEM) and high resolution transmission electron microscopy (HRTEM) and electron diffraction. Morphologically, the similar homogeneous, dark, metallic and adhesive appearanceshave been revealed for all the coats deposited on various substrates (by SEM). However, using HRTEM in agreement with electron diffraction, different phase composition on various substrates has been detected. Cubic pyrite phase (FeS2) has been detected on Ta substrate. Cubic pyrite (FeS2) and metastable rhomboedric smythite Fe9S11 have been found in case of Al substrate. Cubic pyrite (FeS2), metastable rhomboedric smythite Fe9S11 and metastable orthorhombic marcasite (FeS2m) revealed HRTEM analysis of the film on Cu substrate. In case of all deposits the detected crystalline nanograins were surrounded by amorphous matrix

Geometrical features in longitudinal sputtering hollow cathode discharges for laser applications

Longitudinal sputtering hollow cathode discharge (HCD) used as active medium for lasing is studied by means of numerical modelling. Due to the longitudinal non-uniformities of the discharge, the laser operation could be strongly affected. The non-uniformity of the discharge is mainly influenced by the dimensions of the hollow cathode, in particular by the aspect ratio length/radius. To study the geometrical features, a simulation model for HCDs has been constructed using the Plasimo modelling platform. The model allows in-depth studies of the plasma mechanisms and enables finding the optimum under the working conditions of the HCDs. The model is validated by comparing the results with the experimental observations. The spatial distribution of the plasma density and potential as well as an in-depth discussion of the results and the trends revealed by the model are presented. The proper understanding of the essential geometrical features allowed defining the optimal aspect ratio length/diameter for stable and uniform discharge with high excitation efficiency

Geometrical features in longitudinal sputtering hollow cathode discharges for laser applications

Longitudinal sputtering hollow cathode discharge (HCD) used as active medium for lasing is studied by means of numerical modelling. Due to the longitudinal non-uniformities of the discharge, the laser operation could be strongly affected. The non-uniformity of the discharge is mainly influenced by the dimensions of the hollow cathode, in particular by the aspect ratio length/radius. To study the geometrical features, a simulation model for HCDs has been constructed using the Plasimo modelling platform. The model allows in-depth studies of the plasma mechanisms and enables finding the optimum under the working conditions of the HCDs. The model is validated by comparing the results with the experimental observations. The spatial distribution of the plasma density and potential as well as an in-depth discussion of the results and the trends revealed by the model are presented. The proper understanding of the essential geometrical features allowed defining the optimal aspect ratio length/diameter for stable and uniform discharge with high excitation efficiency

A novel device for spectrochemical analysis based on a combination of LIBS and a hollow cathode discharge

A new modified analytical scheme of laser ablation-hollow cathode discharge (LA- HCD) for elemental analysis is reported. The novelty is the use of a hollow cathode with a longitudinal slit. This slit enables registration of the axial species distribution in the discharge and decoupling of the laser and the analytical signals. In this paper preliminary experiments on the modified LA-HCD set-up are reported. The improved analytical performance of the new LA-HCD scheme is demonstrated by comparing it to stand-alone laser induced breakdown spectroscopy. The results of the modified LA-HCD technique show enhancement of the excitation efficiency

Monte Carlo simulation of electron kinetics in a hollow cathode discharge

A kinetic model is reported computing the electron behavior in a hollow cathode discharge based on the Monte Carlo technique. It is a part of the PLASIMO modelling toolkit. The model allows the electrons to be closely followed while they travel and undergo collisions in the discharge. The Monte Carlo modulewas applied to the case of a HCD used as an excitation medium of atoms obtained by laser ablation. Results are obtained on the electron energy distribution function and the mean electron energy under typical discharge conditions. The output data and future development of the model and its applications are analyzed and discussed