PHOTOLYSIS OF SIH4 BY THE 3RD-HARMONIC OF A ND-YAG LASER AT 355-NM

The photolysis of silane (SiH4) was carried out using the third harmon ic of a Nd: YAG laser at 355 nm, at a Bred SiH4 pressure of 350 Torr, varying the laser energy fluence in the range of 30-300 Jcm(-2). The e mission spectra indicates that the photofragments formed are SiH2, SiH , Si, H-2, and H. The (A(1)B(1)-X(1)A(1)) transitions at 552.7 nm, 525 .3 nm, 505.6 nm, and 484.7 nm of SIH2 are due to a two photon absorpti on process. The (A(2) Delta-X(2) pi) transitions of SiH at 425.9 nm, 4 18 nm, 414.2 nm, 412.8 nm and 395.6 nm are due to a three photon absor ption process. The brownish white deposit on the cell windows indicate s the presence of amorphous silicon (a:Si-H). The two atomic lines of Si(4s(1)P(0) --> 3p(21)D(2)) at 288.1 nm, and (4s(3)P(j) --> 3P(3)P(j) ) at 251.6 nm are observed. The atomic Si transitions are due to a thr ee photon absorption. We observed seven transitions due to molecular h ydrogen 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 absorpti on process. In addition to the molecular bands we also observed hydrog en atomic lines H-beta, H-gamma and H-delta.