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1
Content available remote

Transport Coefficients in Mixtures Ar/H_2

100%
Nikitović Ž., Stojanović V.
Acta Physica Polonica A
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2013
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vol. 123
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issue 1
73-75
EN
In this work we present electron transport coefficients for electrons in Ar/H_2 mixtures for the conditions used in plasma assisted technologies for semiconductor production i.e. in moderate to very high reduced electric field E/N (E - electric field, N - gas density). We used a two term numerical solution of the Boltzmann equation at the lowest E/N and mean energies and also Monte Carlo simulation technique at moderate and high E/N. We show that a good agreement with experimental data exists for low and moderate E/N and that based on the tests for pure H_2 and Ar we can model properly the high E/N development. Results were obtained for abundances of H_2 from 1% to 50%. Such data are required to test the sets of cross-section data which are necessary in kinetic models for this mixture and also to produce transport coefficients for fluid models. Hydrogen is used for etching of organic compounds, most importantly low k dielectrics, at the same time argon as a buffer gas is added to control the mean energy and distribution function. Besides, operation at high E/N allows the generation of fast neutrals for charging free etching on nanometer scales.
2
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Modeling of Excitation by Heavy Particles in Pure H_2 Discharges at High E/N

100%
Stojanović V., Nikitović Ž.
Acta Physica Polonica A
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2012
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vol. 121
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issue 3
622-624
EN
H_{ α} emission profiles were calculated for the high E/N (electric field E to gas density N ratio) Townsend discharges in pure hydrogen. Heavy particle collisions including the fast neutrals and interactions with the cathode surface are also included. The basic data were chosen to be in accordance with those used by Phelps. Monte Carlo simulation technique employing null collision method was used to follow electrons and heavy particles between collisions with H_2 or with surface for the conditions of a high E/N. Trajectories of reaction fragments are followed after the collision until their neutralization or thermalization down to the threshold of H_{ α} excitation. We obtained spatially resolved emission profiles and the Doppler broadened line profiles for the conditions of the experiment of Petrović and Phelps. Intensity of the Doppler profile wing showing H_{ α} emission of particles emerging from the cathode direction is obtained assuming that the reflection coefficient of the fast H atoms depends on the incident angle and on energy of the incident particle.
3
Content available remote

Cross-Sections and Transport Properties of F^{-} Ions in F_2

81%
Stojanović V., Nikitović Ž., Jovanović J., Raspopović Z.
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vol. 125
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issue 1
46-48
EN
We present the new results for the simple scattering cross-section set and proposed transport coefficients for F^{-} ions in F_2 that can be used in such models. Nanbu's theory based on thermodynamic threshold energies and separating elastic and reactive collisions is used to calculate cross-sections for binary collisions of ions with atoms and molecules. Direct MC method is applied to obtain swarm parameters at temperature of T = 300 K.
4
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Transport Coefficients For Electrons in Mixtures CF_4/Ar/O_2 and CF, CF_2 or CF_3 Radicals

81%
Nikitović Ž., Stojanović V., Radmilović-Radjenović M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 2
289-291
EN
Transport coefficients for electrons in mixtures of CF_{4} with Ar and O_{2} for ratios of the electric field to the gas number density E/N from 1 Td to 1000 Td (1Td=10^{-21} V m^2) are presented. The analysis of non-conservative collisions revealed a range of the reduced electric field E/N where electron attachment introduced by radicals significantly changes electron kinetics obtained for mixtures without dissociation of CF_{4} gas. The results obtained by using a simple, Two Term solutions for Boltzmann's equation are verified by Monte Carlo simulations. It was found that three body attachments for oxygen is not significant for pressures that are standard in plasma etching equipment i.e. below 1 Torr. Furthermore, the attachment to CF, CF_{2} and CF_{3} at low mean energies is significant, several orders of magnitude. At the same time the mean energy and energy distribution functions for the given E/N are the same as in unperturbed gas mixture. The large changes of the attachment rate are sufficient to change the nature of plasmas and turn them into ion-ion plasmas with very few electrons for realistic abundances.
5
Content available remote

On the Role of Radicals in Kinetics of Plasma Etchers in Ar/CF_4 Mixtures

81%
Nikitović Ž., Stojanović V., Petrović Z.
Acta Physica Polonica A
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2009
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vol. 115
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issue 4
765-767
EN
In this paper we present the transport coefficients in Ar/CF_4 mixtures with realistic abundances of CF_x radicals, F atoms, and F_2 molecules that are standard products of plasma chemistry in plasma etching systems and are present in large abundances of the order of few percent in realistic plasma etching devices. It was found that, although radicals make a minimum impact on distribution function and mean energy, the effect on drift velocity is significant and the effect on rates of attachment is large and may change the mode of operation of plasmas.
6
Content available remote

Transport Parameters of F^- Ions in BF_3

81%
Nikitović Ž., Stojanović V., Raspopović Z., Jovanović J.
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vol. 126
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issue 3
724-727
EN
In this work we presented the new results for energy dependent cross-sections and transport coefficients as a function of E/N for F^- ions in BF_3 gas. Results were obtained by using the Monte Carlo technique for cross-section set determined on the basis of the Nanbu theory. Monte Carlo method is applied to obtain swarm parameters at temperature of T=300 K.
7
Content available remote

Cross-Section and Transport Parameters of Ne⁺ in CF₄

81%
Nikitović Ž., Stojanović V., Raspopović Z.
Acta Physica Polonica A
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2016
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vol. 130
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issue 6
1343-1345
EN
A cross-section set for scattering Ne⁺ ions in CF₄ is assessed by using available experimental data for charge transfer cross-sections. In this paper we present new results for the mean energy, reduced mobility and diffusion coefficients for low and moderate reduced electric fields E/N (N - gas density) and account for the non-conservative collisions. The Monte Carlo method is used to calculate transport properties of Ne⁺ ions in CF₄ at temperature of T=300 K.
8
Content available remote

Phonon Contribution in Thermodynamics and Transport Properties of Ultrathin Ceramic Films

81%
Jaćimovski S., Šetrajčić J., Jaćimovski M., Stojanović V.
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vol. 126
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issue 3
811-820
EN
The dispersion law, density states of phonons, thermodynamics properties and thermal conductivity was analyzed in this paper. It has been shown that at low temperatures, thermal conductivity of thin film is considerably lower that of bulk-structure. It turned out that phonons in thin film require activation energy for exciting. This leads to extremely low specific heat and specific conductivity at low temperatures. Consequences of quoted facts were discussed in detail and their influence on kinetic and thermodynamic properties of thin films is estimated.
9
Content available remote

Rate Coefficients of F^{-} Ions in Ar/BF_{3} Mixtures

81%
Nikitović Ž., Stojanović V., Raspopović Z.
Acta Physica Polonica A
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2015
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vol. 127
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issue 6
1634-1636
EN
Transport parameters of F^{-} ions in mixtures Ar/BF_{3} in DC fields were calculated using Monte Carlo simulation technique assuming the scattering cross-section set assembled on the basis of Nanbu's technique separating elastic from reactive collisions. In this work we present characteristic energy and rate coefficients for low and moderate reduced electric fields E/N (N - gas density) and account for the non-conservative collisions.
10
Content available remote

H⁺ Scattering in n-Butanol

81%
Nikitović Ž., Raspopović Z., Stojanović V.
Acta Physica Polonica A
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2017
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vol. 132
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issue 4
1420-1423
EN
In this paper we show predictions for the low energy cross-sections and transport properties for the H⁺ in n-butanol gas. These data are needed for modelling in numerous technologically important applications. Appropriate gas phase enthalpies of formation for the products were used to calculate scattering cross-section as a function of kinetic energy. Calculated cross-sections can be used to obtain transport parameters as a function of E/N (E - electric field, N - gas density) for H⁺ in n-butanol gas.
11
Content available remote

Modeling of Electron Kinetics in BF_{3}

62%
Nikitović Ž., Šašić O., Raspopović Z., Stojanović V., Radovanov S., Mozetič M., Cvelbar U.
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issue 5
748-751
EN
In this paper we used the available data for the electron impact scattering cross sections BF_{3} to calculate the transport coefficients for electrons. Monte Carlo simulation was used to perform calculations of the transport coefficients as well as the rate coefficients in DC electric fields, crossed electric and magnetic DC and RF fields.
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