Relative Kinetic Energy Range Research Articles

Elastic scattering of ruthenium atoms from Si and O atoms in the range of relative kinetic energies of 2-200 eV

Interconnector technologies of a new generation involve the use of ruthenium. The high cost of experimental study of sputtering and etching of trenches in Ru leads to the need to optimize it by modeling that requires knowledge of the cross sections of elementary processes of interaction of plasma particles with Ru. In this work, the binary interatomic potentials of Ru-Ru and Ru-Si pairs tested by the molecular dynamics method, and the Ru-O one calculated by the method of multi-reference configurational interaction MRCI/AV5Z were used to calculate the elastic scattering cross sections of the atomic pairs in the energy range typical of plasma etching chambers. Keywords: ruthenium, elastic scattering, cross sections, sputtering, binary potential.

Упругое рассеяние нейтрального фтора на атомах Si, O, C и H в диапазоне относительных кинетических энергий 2-200 eV

Binary interatomic potentials F-F, F-Si, F-O, F-C and F-H are calculated from the first principles (ab initio) on the basis of the multi-configuration method of self-consistent field (CAS-SCF) with a basic set of atomic wave functions aug-pp-AV6Z and are used to calculate phase shifts and cross sections of elastic scattering of atoms in the range of relative kinetic energies 2-200 eV. It is expected that the obtained elastic scattering cross sections will be useful for describing sputtering and etching of porous organosilicate films with ethylene bridges used in modern nanoelectronics.

Elastic Scattering of Mo-Mo, Mo-S and S-S Atomic Pairs in the Relative Kinetic Energy Range of 2–200 eV

The interatomic binary potentials of Mo-Mo, Mo-S and S-S, approved by Molecular Dynamics, were used to calculate elastic phase shifts and cross sections of the atomic pairs in the relative kinetic energy range of 2–200 eV. It is expected the obtained differential and integral cross sections to be of help to describe sputtering of MoS2 nanometer layers in design of perspective devices of nanoelectronics and photonics.

Упругое рассеяние атомных пар Mo-Mo, Mo-S и S-S в диапазоне относительных кинетических энергий 2-200 eV

AbstractThe interatomic binary potentials of Mo-Mo, Mo-S and S-S, approved by Molecular Dynamics, were used to calculate elastic phase shifts and cross sections of the atomic pairs in the relative kinetic energy range of 2–200 eV. It is expected the obtained differential and integral cross sections to be of help to describe sputtering of MoS_2 nanometer layers in design of perspective devices of nanoelectronics and photonics.

Elastic scattering process for argon ions and oxygen atoms in 10-500 eV range of relative kinetic energies

SynopsisThe interaction potential between oxygen atoms (3P state) and argon ions (2P state) has been calculated on ab initio level in the vast range of internuclear distances (0.8-100 a.u.). The elastic scattering process has been studied for relative kinetic energies of 10-500 eV.

Elastic scattering of an oxygen atom on a silicon atom in the 10–500 eV range of relative kinetic energies

The potential of interaction between oxygen and silicon atoms in a range of interatomic distances within 0.75–11.5 au has been calculated from first principles (ab initio) using the multiconfigurational interaction (MRCI) method with the aug-pp-AVQZ basis set of atomic wave functions. An analytical approximation of the numerically calculated potential is presented. The elastic scattering of oxygen on silicon was studied in the 10–500 eV range of relative kinetic energies. The obtained differential, integral, and transport scattering cross sections and the proposed interatomic potential can be used in the field of nanotechnologies.

Experimental investigation of electron impact onSi2−

A merged beams technique has been used to investigate collisions between electrons and $\text{Si}_{2}{}^{\ensuremath{-}}$ ions over a relative kinetic energy range of 0--210 eV. Absolute cross sections for pure electron detachment, detachment plus dissociation, and dissociation involving atomic and ionic products were measured. The dominant process over the energy range studied is pure electron detachment. A search for a resonance associated with a ${\text{Si}}_{2}$ dianion was made but none was observed.

Reaction of Metastable Ar*(3P2) and Kr*(3P2) Atoms with Water Vapor: Excitation Functions for Electronic Quenching Collisions

In this paper, we examine the functional nature of the state-specific cross section for electronic quenching σQ(E) in collisions of metastable noble gas atoms [Ar*(3P2) and Kr*(3P2)] with ground-state water molecules confined to a scattering-gas cell. The relative kinetic energy range studied is E = 0.0463−0.772 eV for Ar*(3P2) and 0.0432−0.692 eV for Kr*(3P2). These beam-gas-luminescence experiments incorporate a novel state-specific monitor system employing Xe gas. Photon emission from a state-specific Xe state produced in quenching collisions with the respective metastable noble gas (Ng*) atoms is a direct measure of the total disappearance of the metastable state under scrutiny in the reaction with water vapor. We use the classical orbiting and absorbing sphere models with empirically derived parameters [London dispersion Cdisp, induction Cind (spherically averaged or aligned dipole), and absorbing sphere radius ras] to predict energy-dependent cross sections for the total quenching reactions. The underlying premise of the models is that although the quenching process itself is envisioned to be a short-range two-electron exchange interaction, it is the long-range attractive forces between the respective collision partners that are critical in determining whether such short-range processes ultimately occur. Values of σQ determined from the models are in very good agreement with our experiment. This work supersedes our previous study for Ar*(3P2,0) [Novicki, S.; Krenos, J. J. Chem. Phys. 1988, 89, 7031].

State selected reactions of krypton ions with methane

Using a photo-electron product-ion coincidence method, the reactions of Kr +( 2P 1/2,3/2) ions with methane molecules are studied in the relative kinetic energy range between 0.1 and 1 eV. The relative total cross-sections and the branching ratios for production of CH 4 + and CH 3 + are determined selectively for the two krypton ions. Using available absolute reaction rates for unselected krypton ions, absolute selective rates are obtained. In addition, a simple model is presented that describes the reactions quantitatively in terms of two distinct mechanisms: (1) reactions via “close collisions”, and (2) reactions via charge exchange in “distant collisions”. Based on this model, evidence for breakdown of the “orbiting transition state theory” for the description of the close collision complex at collision energies above about 0.4 eV, is obtained.

Ion pair production and chemi-ionisation in collisions of He*(21,3S) with Li

A merging-beams technique has been used to study collisions of He*(21,3S) with Li. The He* represents a composite of 13% He(21S) and 87% He(23S). Absolute and relative cross sections, Q, have been measured in a range of relative kinetic energy, W, from 150 to 1500 eV for the ion pair production (IPP) of He++Li-, and from 0.01 to 500 eV for chemi-ionisation (CI) (i.e. Penning ionisation and associative ionisation). The relatively small (<AA2) and monotonically increasing Q with W for IPP is qualitatively explained on the basis of poor coupling in at least the first step of a ladder-climbing process between the incoming covalent and outgoing ionic potentials. Attempts to observe signals for IPP of He-+Li+ were obscured by noise. Information obtained for CI shows that: the Penning ionisation reaction is directed with most of the Li+ scattered in the incident Li direction, the He*-Li system is attractive with a measured well depth of 0.73 eV and the value of Q for total ionisation varies as W-0.34. Similarities to the He*-He* system are also given.

Formation of N 2(B 3 Π g) in collisions between metastable Xe(6s 3P 2,0) and N 2(X 1∑ +g)

Vibrational population ratios for N * 2(B) formed by Xe */N 2 collisions were measured over the relative kinetic energy range 0.04–0.2 eV. Golden rule and ionic-intermediate curve-crossing models predict population ratios for v' = 2-4 in good agreement with experiment, but fail to account for the dominant channel v' = 5.

Rate constants for the reactions of metastable O+ ions with N2 and O2 at collision energies 0.04 to 0.2 eV and the mobilities of these ions at 300 K

The reactions of metastable O+* ions with N2 and O2 have been examined in a selected-ion flow-drift tube over the relative kinetic energy range from thermal to 0.2 eV. The rate constants are found to be (8.5±3.4)×10−10 and (8.1±3.2)×10−10 cm3 s−1, respectively, at these energies. These values are essentially equal to the gas-kinetic limiting values. The principal reaction mechanism in both cases is charge transfer. Based on molecular beam studies of the ion-source reaction thought to produce the present O+* ions, it appears likely that they are largely O+(2D°) ions. The present results for these reactions are in good agreement with the results of most of the earlier studies, which were limited to either thermal or elevated collision energies. However, the present data for O+*+N2 appear to conflict with the much smaller rate constant predicted for the reaction of O+(2D°)+N2 from analyses of satellite data. As a necessary part of this study, the mobilities of the O+* ions in helium were determined and are 7% to 11% less than those of the ground-state O+ ion.

Cross-section for the reaction O − + O 2 → O 2− at relative kinetic energies from threshold to 3 eV

The cross-section for the charge-transfer reaction of O − with O 2 is determined in the relative kinetic energy range from 1 eV (threshold) to about 3 eV, using a combination of experimental and theoretical ion-swarm techniques. Reaction rate constants are measured in a helium-buffered flow-drift tube in the range 50 ≤ E/N ≤ 110 Td, where E is the DC electric field strength, N is the helium gas number density and 1 Townsend (Td)  10 −17 V cm 2. Velocity distributions are computed using Monte Carlo techniques for O − ions drifting in helium at E/N values in this range. These distributions and the drift-tube rate constants define the reaction cross-section at low collision energies, a region in which it has been difficult to make reliable ion-beam measurements.

Long-range helium excimer potentials (A,CΣu,g+1anda,cΣu,g+3) from high-resolution differential cross sections for He(2S1,2S3)+He

The long-range parts of the A,C /sup 1/..sigma../sup +//sub u/,g and a,c /sup 3/..sigma../sup +//sub u/,g excimer potentials of the He/sub 2/ molecule have been accurately determined from high-resolution differential-cross-section measurements in the relative kinetic-energy range from 18 to 140 meV. The barrier heights and internuclear distances of the intermediate maxima of the A and the a state have been obtained with an accuracy of better than 2--5 meV and 0.1 A, respectively. The long-range parts of the singlet potentials from the ab initio calculation by Gubermann and Goddard are always 5--20 meV higher than the potential determined from our experiments, but the splitting of the potentials coincides with our results within experimental accuracy for R > or = 3 A. The experimental setup, data evaluation, and the construction of the potential are described in detail. The complicated interference structure of the angular distribution is discussed with the help of the quantal deflection function. Total and excitation-transfer cross sections are calculated and compared to other experimental results, and the similarity to other exchange processes is pointed out.

Transfer of electronic excitation in collisions of metastable argon atoms with nitrogen molecules

Measurements have been made of the product vibrational and rotational state distributions for the process Ar*(3P2,0)+N2(X) →Ar(1S0)+N2*(C,3Πu) by spectrometric observation of the C→B fluorescence at the intersection of supersonic beams of the reactant species over the relative kinetic energy range 0.06–0.41 eV. The results are compared with the predictions of a ’’golden rule’’ model which gives the transition probabilities in the highly impulsive limit as the product of Franck–Condon and density of states factors. Below 0.17 eV, the model fits the experimentally determined v′=0/v′=1 population ratio reasonably well. At higher energies the experimental ratio rises, however, and reaches a maximum at 0.3 eV. A statistical population of rotational levels for v′=0 corresponding to rotational temperatures of 1300 °K and 1100 °K at 0.161 and 0.089 eV relative energy, respectively, is observed, while the ’’golden rule’’ predicts considerably higher rotational excitation in each case.

Ion pair formation and atom abstraction in collisions of Cs and UF6

The ion pair formation reaction Cs+UF6→Cs++UF6− and the atom abstraction reaction Cs+UF6→CsF+UF5 have been studied over the relative kinetic energy range 0.2 to 1.3 eV using a seeded nozzle source for UF6. The cross section for ion pair formation was found to increase with the kinetic energy and a value of 32 Å2 was observed at 1.3 eV. Unlike previous results at thermal energies, the angular distributions of CsF provided no indication of complex formation but were found to be peaked in the backward (c.m.) direction. Estimates of the abstraction reaction cross section show it to be the dominant channel in this energy range.

Total cross sections for K + Br 2 at relative energies between 0 and 8000 eV

Trajectory Surface Hopping (TSH) calculations have been applied to the non-elastic scattering in the K + Br 2 collision system over a wide range of relative kinetic energies from 0 to 8000 eV. Absolute total cross sections have been computed for the formation of various collision products with an accuracy of 5% with respect to statistical errors. The following non-elastic processes have been studied: chemical reaction, inelastic neutral scattering, neutral dissociation and ion pair formation, yielding atomic as well as molecular negative bromine ions together with PC ions. The absolute values of the respective total cross sections, obtained from the TSH calculations, are in close agreement with the available experimental data, both for chemical reaction and for ion pair formation, over the whole energy range considered. The three particle character of the collision system is important in describing the experimental results quantitatively at relative kinetic energies below 100 eV.

The dynamics of the reaction H+2+H2→H+3+H, with isotopic variations

We performed a merged-beam study of the reactions HD++D2→HD+2+D, D+3+H, D+2+HD→HD+2+D, D+3+H, in which we measured the absolute reaction cross sections, branching ratios, and product energy distributions over the range of relative kinetic energy from ∼0.002 to 8 eV. Within the experimental uncertainty all three types of data are identical for the two reactant charge states at initial kinetic energies less than 0.5 eV, leading us to believe that adiabatic charge equilibration between the reactants occurs prior to reaction at these low energies. Diabatic behavior becomes increasingly dominanant at higher energies. The reaction mechanism is direct and products are formed with a broad distribution of translational energies. In low energy collisions, on the average, a small fraction of the reaction exothermicity and the reactant excitation energy is converted into translational energy of the products. At higher energies there is a net conversion of translational into internal energy. The reaction energetics are not in agreement with stripping model predictions.

The dynamics of the reaction D+2+O(3P) →OD++D, and the influence of the atomic quadrupole moment on the cross section at very low kinetic energies

We report the results of a merged-beam study of the reaction D+2+O(3P) →OD++D over the range of relative kinetic energy from 0.002 to 27 eV. The data include accurate absolute values of the total reaction cross section and also high-resolution measurements of the product ion laboratory energy distributions, which are deconvoluted to obtain estimates of the product energy and angle distributions in c.m. coordinates. The reaction mechanism is direct, with the OD+ product scattered preferentially in the direction of the incident O atom, and with large average internal excitation. The fact that O(3P) possesses an electrostatic quadrupole moment has important consequences for the interpretation of the low-energy data in terms of the adiabatic state correlations of reactants, intermediates, and products. Our major conclusions are (1) that the average probabilities of reaction for low-energy capture collisions are about 87% for approaches on Σ−–A2 potential energy surfaces and about 53% for approaches on Π–B1, B2 surfaces and (2) that the data are not consistent with the assumption of electronic adiabaticity.

High-Resolution Atomic Beam Study of the Helium Excimer PotentialsHe2(A, CΣu,g1+)

The long-range parts of the $A$, $C{^{1}\ensuremath{\Sigma}_{\mathrm{u},\mathrm{g}}}^{+}$ excimer potentials of the ${\mathrm{He}}_{2}$ molecule have been accurately dtermined from high-resolution differential-cross-section measurements at the relative kinetic energy range from 18 to 140 meV. The barrier height of the intermediate maximum of the $A{^{1}\ensuremath{\Sigma}_{\mathrm{u}}}^{+}$ potentials is ${47}_{\ensuremath{-}1}^{+2}$ meV at an internuclear distance of 3.14 \ifmmode\pm\else\textpm\fi{} 0.05 \AA{}. The long-range parts of the potential from the recent ab initio calculation by Guberman and Goddard is always 5 to 20 meV higher than the potential determined from our experiments.