Photolysis of Disilane at 193 nm

Abstract

The primary photochemical process of Si2H6 at 193 nm has been studied by using time-resolved mass spectrometry and laser-induced fluorescence (LIF) techniques. Si2H2 was confirmed as a primary photoproduct, but no signal due to SiH3, Si2H3, Si2H4, and Si2H5 in 193 nm photolysis has been detected. SiH2 was observed in a pump-and-probe experiment by the LIF method, which rapidly reacts with the Si2H6 parent molecule to form Si3H8. The quantum yield of Si3H8 produced in the reaction of SiH2 + Si2H6 was estimated to be 0.13 ± 0.02 by using electron impact mass spectrometry. It was concluded that SiH2 produced by the photolysis exclusively reacted with Si2H6 and thus the quantum yield of SiH2 was equal to that of Si3H8, i.e., 0.13. The quantum yield of H atom was estimated to be 0.09 ± 0.01 by using vacuum ultraviolet (VUV) LIF. On the basis of the existing data and present results, it was suggested that the H2 molecule production channels are dominant in 193 nm photolysis of Si2H6.

Kinetics of Si2H2 produced by the 193 nm photolysis of disilane

“…If the fast decay at m/z ϭ 58 shown in Figure 2 is governed by the reaction of Si 2 H 2 with H atom, the concentration of H atom must be greater than that of Si 2 H 2 . The quantum yield for production of H atom has been reported to be 0.1 [18]. Although we simulated time profiles of Si 2 H 2 by changing the reaction rate constant of Si 2 H 2 with H atom and concentration of Si 2 H 2 , the simulated profiles are far from that obtained in experiments.…”

“…The experimental setup for PI-MS has been described in detail elsewhere [18]. A vacuum chamber was pumped by a 500 l/s turbo molecular pump to a base pressure of 2 ϫ 10 Ϫ7 Torr.…”

“…The following samples were used without further purification: Helium (Nippon Sanso, 99.9999%), Si 2 H 6 /He (Nippon Sanso, 1.03%), SiH 4 /He (Nippon Sanso, 1.04%), H 2 /He (Nippon Sanso, 1.07%). been assigned to the main photoproducts in the 193-nm photolysis of Si 2 H 6 [18]. The rise time of the signal was limited by the time resolution of the detection systems, which is mainly controlled by a traveling time of molecules from a reaction zone in the photolysis cell to an ionization region.…”

“…The adiabatic ionization potentials of the dibridged (1), monobridged (2) where [Si 2 H 6 ] and are Si 2 H 6 concentration and absorption cross sections, respectively, and N p is photon density as determined from laser pulse energy measurements. Tada et al [18] summarized the dissociation pathways and their branching fractions in the 193-nm photolysis of Si 2 H 6 . According to their results, the upper limit of quantum yield () for the production of Si 2 H 2 is estimated to be 0.44.…”

“…He has argued that the signals are due to some members of the family Si 2 H n (2 Շ n Շ 4), but the assignments were highly speculative. Most recently, Tada et al [18] observed Si 2 H 2 produced from the 193-nm photolysis of Si 2 H 6 using time-resolved photoionization mass spectrometry (PI-MS). The time profile of Si 2 H 2 showed the fast decay, indicating that the species would be attributed to an unstable species.…”