Laser desorption ionization time-of-flight mass spectrometric study of binary As-Se glasses

Binary chalcogenide As-Se glasses and their thin films are important for optics, computers, materials science and technological applications. To increase understanding of the properties of thin films fabricated by plasma deposition techniques, more information concerning the physics of plasma plume is needed. In this study the formation of clusters in plasma plume from different As-Se glasses by laser desorption ionization (LDI) or laser ablation (LA) was studied by time-of-flight mass spectrometry (TOF MS) in positive and negative ion modes. Formation of a number of As(p)Se(q) singly charged clusters As(3)Se(q)(+) (q = 1-5), AsSe(q)(-) (q = 1-3), As(2)Se(q)(-) (q = 2-4), and As(3)Se(q)(-) (q = 2-5) was found from As-Se glasses with the molar ratio As:Se in the range from 1:2 to 7:3. The stoichiometry of the As(p)Se(q) clusters was determined via isotopic envelope analysis and computer modeling. The structure of the clusters is proposed and the relationship to the structure of the parent glasses, as also suggested by Raman scattering spectra, is discussed.