Excimer laser ablation of graphite: The enhancement of carbon dimer formation

Ursu, Cristian; Nica, P.; Focşa, Cristian

doi:10.1016/j.apsusc.2018.06.217

Cited by 19 publications

(11 citation statements)

References 46 publications

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“…The V-like shape becomes observable at LP = 44 cm, while for LP = 46 cm, the two plasma "seeds" appear to be completely separated. In previous works [20,21], we observed some correlations with the ablation crater depth profile. Thus, for LP = 41 cm and LP = 42, its shape is mirroring the laser energy distribution, but for LP = 46 cm, two ablation depths were observed, with a deeper hole in the crater center and two lateral thresholds at distances similar with the long axis of the laser beam [20,21].…”

Section: Complexitysupporting

confidence: 61%

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Fractal Method for Modeling the Peculiar Dynamics of Transient Carbon Plasma Generated by Excimer Laser Ablation in Vacuum

Ursu¹,

Nica

Focşa

et al. 2018

Complexity

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Carbon plasmas generated by excimer laser ablation are often applied for deposition (in vacuum or under controlled atmosphere) of high-technological interest nanostructures and thin films. For specific excimer irradiation conditions, these transient plasmas can exhibit peculiar behaviors when probed by fast time- and space-resolved optical and electrical methods. We propose here a fractal approach to simulate this peculiar dynamics. In our model, the complexity of the interactions between the transient plasma particles (in the Euclidean space) is substituted by the nondifferentiability (fractality) of the motion curves of the same particles, but in a fractal space. For plane symmetry and particular boundary conditions, stationary geodesic equations at a fractal scale resolution give a fractal velocity field with components expressed by means of nonlinear solutions (soliton type, kink type, etc.). The theoretical model successfully reproduces the (surprising) formation of V-like radiating plasma structures (consisting of two lateral arms of high optical emissivity and a fast-expanding central part of low emissivity) experimentally observed.

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Section: Complexitysupporting

confidence: 61%

“…The experimental setup used for measurements is described in details in [19][20][21]. Briefly, carbon plasma has been produced by the ablation of high-purity (99.99%) pyrolytic graphite targets placed in an evacuated chamber (0.0001 Pa) using a KrF excimer laser (248 nm, 20 ns, and 5 Hz).…”

Section: Experimental Aspectsmentioning

confidence: 99%

Fractal Method for Modeling the Peculiar Dynamics of Transient Carbon Plasma Generated by Excimer Laser Ablation in Vacuum

Ursu¹,

Nica

Focşa

et al. 2018

Complexity

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“…The basic technology of cryogenic buffer gas cooling has been developed and refined over the past two decades [61,63]. Hot carbon vapor to seed the buffer gas cell can be created via ablation of a graphite target [64,65] or evaporation of graphite rods via resistive heating [66]. These have been shown to generate vapor containing mixtures of various carbon compounds, including C, C 2 , C n , fullerenes, etc., whose exact ratios can be controlled by varying experimental parameters.…”

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confidence: 99%

“…These have been shown to generate vapor containing mixtures of various carbon compounds, including C, C 2 , C n , fullerenes, etc., whose exact ratios can be controlled by varying experimental parameters. For example, ablation sources can produce carbon beams with a typical composition of ∼ 10% of C 2 [64] and it has been shown that beam shaping of the ablation pulse can further enhance the formation of C 2 [65]. In the ablation process a significant C 2 fraction is found to be produced in the triplet states of a 3 Π u [65,67].…”

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Laser Cooling Scheme for the Carbon Dimer ($^{12}$C$_2$)

Bigagli,

Savin,

Will

2021

Preprint

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“…Complex space charge structures such as fireballs, multiple double layers, plasma bubbles, and solitons offer exciting study grounds for both experimentalists and theoreticians. C. Ursu et al in "Fractal Method for Modeling the Peculiar Dynamics of Transient Carbon Plasma Generated by Excimer Laser Ablation in Vacuum" propose a fractal approach to simulate the formation of (surprising) V-shape radiating plasma structures (consisting of two lateral arms of high optical emissivity and a fast expanding central part of low emissivity), which have been previously observed [12]. In their model, the complexity of the interactions between the transient plasma particles (in the Euclidean space) is substituted by the nondifferentiability (fractality) of the motion curves to the same particles, but in a fractal space.…”

mentioning

confidence: 99%

Fractal‐Type Dynamical Behaviors of Complex Systems

et al. 2018

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This special issue of Complexity initially aimed at gathering leading-edge up-to-date studies showcasing the occurrence of fractal features in the dynamics of highly nonlinear complex systems. More than thirty years after coining term by Mandelbrot [1], fractals continue to fascinate the scientific community or the general public, with their wonderful propensity to infinitely repeat the same patterns at various (spatial and/or temporal) scales. On a more specialized ground, these continuous but nondifferentiable mathematical objects have become increasingly useful tools in developing original approaches to efficiently model natural or physical phenomena which escape from the traditional horizon of Euclidean metrics. Their range of applications is tremendously wide, from the well-known initial quest of measuring the length of Britain coast [2] to the most recent investigations on digital image processing for materials science [3], chaotic circuits [4], information technology [5], and medicine [6]. Initially developed at macro/mesoscopic scales, these objects penetrate now the nanoworld [7] with the development of ultrahigh resolution probes. At a temporal level, modeling of ultrafast phenomena (as peculiar oscillations evidenced in transient laser-generated plasmas [8]) can benefit from innovative scale relativity of fractal-based theoretical developments [9].Although appealing, the initial fractal-oriented scope of this special issue has been proven to be quite sharp, and the decision was taken, in agreement with the journal editorial board, to broaden its range to a more general nonlinear dynamic field. In this context, 17 papers have been received for review, covering a wide variety of topics, from "pure" mathematics and theoretical physics to applications in materials science, plasma physics, medicine, and financial markets. Despite the high quality of all submitted papers, the very rigorous review process retained only seven of them for publications in this special issue. A brief presentation of each accepted paper is given in the following.In "Analysis of Implicit Type Nonlinear Dynamical Problem of Impulsive Fractional Differential Equations," N. Ahmad et al. use a powerful combination of Caputo fractional derivatives and classical fixed point theorems (Banach and Krasnoselskii) to investigate the existence, uniqueness, and various kinds of Ulam-Hyers stability [10] of the solutions to impulsive fractional differential equations with nonlocal boundary conditions. A "pure" mathematical object, the Ulam concept of stability [10], finds quite significant applications in real-world problems like the formation of rogue waves (tsunami) in the oceans or the design of ultrahigh precision optical clocks. A very recent example is offered by the observation in optical fibers of the broken symmetry of Fermi-Pasta-Ulam recurrence [11]. In another "mathematical" paper of this special issue ("Moderate Deviations for Stochastic Fractional Heat Equation Driven by Fractional Noise"), X. Sun et al. use a fractional Laplacian ...

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Excimer laser ablation of graphite: The enhancement of carbon dimer formation

Cited by 19 publications

References 46 publications

Fractal Method for Modeling the Peculiar Dynamics of Transient Carbon Plasma Generated by Excimer Laser Ablation in Vacuum

Fractal Method for Modeling the Peculiar Dynamics of Transient Carbon Plasma Generated by Excimer Laser Ablation in Vacuum

Laser Cooling Scheme for the Carbon Dimer ($^{12}$C$_2$)

Fractal‐Type Dynamical Behaviors of Complex Systems

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