Photolysis of SiH₄ by the Third Harmonic of a Nd:YAG Laser at 355 NM

Abstract

The photolysis of silane (SiH₄) was carried out using the third harmonic of a Nd: YAG laser at 355 nm, at a fixed SiH₄ pressure of 350 Torr, varying the laser energy fluence in the range of 30–300 Jcm^-2. The emission spectra indicates that the photofragments formed are SiH₂, SiH, Si, H₂, and H. The (A¹B₁-X¹A₁) transitions at 552.7 nm, 525.3 nm, 505.6 nm, and 484.7 nm of SiH₂ are due to a two photon absorption process. The (A²Δ-X²π) transitions of SiH at 425.9 nm, 418 nm, 414.2 nm, 412.8 nm and 395.6 nm are due to a three photon absorption process. The brownish white deposit on the cell windows indicates the presence of amorphous silicon (a:Si-H). The two atomic lines of Si(4s¹P⁰→ 3p²¹D₂) at 288.1 nm, and (4s³P_j→ 3P³P_j) at 251.6 nm are observed. The atomic Si transitions are due to a three photon absorption. We observed seven transitions due to molecular hydrogen at wavelengths 577.5 nm, 565.5 nm, 534.4 nm, 542.5 nm, 471 nm, 461.7 nm, and 455.4 nm. These bands are due to a four photon absorption proc6ss. In addition to the molecular bands we also observed hydrogen atomic lines Hβ, Hγ and Hδ.