PHOTON-STIMULATED ION DESORPTION FROM CONDENSED SICL4 BY RESONANT EXCITATION AT THE K-EDGES

Photon-stimulated desorption of fragment and molecular ions from condensed SiCl4 following the Si 1s and Cl 1s excitations has been investigated using synchrotron radiation, The Si+, Cl+, SiCl+ and SiCl3+ ions were observed almost in comparable intensity at the Sits excitation. The presence of atomic Si+ ions is interpreted by the formation of SiCl4n+ (n greater than or equal to 3) ions through KLL and successive LVV Anger decay. On the other hand, more than 80% of the desorbed species were Cl+ ions by the Cl 1s excitation, which suggests that the multiple charges produced by the Auger decay localize on the chlorine atom. The photon-energy dependence of the Cl+ yield revealed that the Cl+ yield at the Cl 1s --> sigma*(8a(1)) resonance excitation is higher than that at the Cl 1s --> sigma*(9t(2)) resonance excitation. It was also found that the excitation at the energy higher than Cl 1s --> sigma* resonance scarcely induces the Cl+ desorption. The high desorption yield at the Cl 1s --> sigma*(8a(1)) resonance is interpreted by the fact that the ga, orbital into which the Cl 1s electron is excited is mostly composed of the Cl 3p* antibonding state, which reduces the binding energy of the Si-Cl bond.