A full dimensionalab initiodynamics study on the ionization processes of CF₄

Abstract

The ionization dynamics of CF4, which plays an important role in the initial processes of plasma dry etching on a silicon surface, has been investigated by means of both static ab initio molecular orbital (MO) and full dimensional direct ab initio dynamics calculations. The static ab initio MO calculation (MP4SDQ/6-311G(d, p) level) showed that the CF4+ ion has a structure that is strongly distorted from Td symmetry and which is expressed by CF3+-F. The complex is 5.8 kcal mol-1 more stable in energy than its dissociation limit (CF3+ + F). From the dynamics calculations (HF/6-311G(d, p) level), it was found that CF4+, formed by the vertical ionization of CF4, decomposes directly into CF3+ and F via the complex region corresponding to CF3+-F. The lifetime of the CF3+-F complex is extremely short and may be neglected. The analysis of the product states showed that 65% of the total available energy is partitioned into the relative translational mode between CF3+ and F. The C-F stretching mode of CF3+ is still in the ground state after the dissociation, whereas the CF3 umbrella mode is excited to v = 1-2. The mechanism of the ionization of CF4 is discussed on the basis of the calculations in this paper.

Helicity-dependent dissociative tunneling ionization of CF4 in multicycle circularly polarized intense laser fields

“…The electronic configuration is expressed as Á Á Á(1e) 4 (4t 2 ) 6 (1t 1 ) 6 . Because of the dissociative nature of the cation in the X 2 T 1 and A 2 T 2 states [39][40][41][42][43][44] (see Fig. 1), the CF 4 + parent ion formed by the tunneling ionization from the 1t 1 HOMO or 4t 2 HOMOÀ1 undergoes direct dissociation to fulfill the axial-recoil condition for the RFPAD measurements.…”

Resonance signatures in the body-frame valence photoionization of CF4

“…The 17 , which has little effect on the dissociation to CF + 3 + F products. The A 2 T 2 surface, on the other hand, which is evidently steeply repulsive in the Frank-Condon region, shows no minimum and therefore dissociates impulsively 14 .…”

Non-equilibrium x-ray spectroscopy using direct quantum dynamics

“…It is noted that the broadband nature of the near-infrared pulse means that experimentally the lowest three ion states are initially populated. However, only the lowest state is dissociative, 63,64 and the higher lying bound ion states strongly coupled to the lowest states and rapidly undergo internal conversion to the lowest ion state in <10 fs. 65 Figure 2 shows the average C-F bond length of the dissociating bond using 10, 20, 40, and 60 GBFs for vMCG (a) and clMCG (b).…”