Interaction of F-2 excimer laser pulses with hydroxy groups in SiO2 glass:Hydrogen bond formation and bleaching of vacuum ultraviolet absorption edge

Excitation of vacuum ultraviolet absorption band of SiOH groups by F-2 exci mer laser photons (7.9 eV) was performed for synthetic SiO2 glasses. Irradi ation induced two concurrent optical changes; red-shift of SiOH infrared ab sorption band and bleaching of vacuum ultraviolet absorption edge which is primarily controlled by SiOH absorption. These optical changes have the sam e origin, that is, the structural alternation of SiOH from isolated to meta stable hydrogen-bonded states. The F-2-induced hydrogen-bonded state was th ermally stable to similar to 300 degreesC and the kinetic barrier for the t hermal relaxation was similar to1.7 eV. The formation of hydrogen-bonded st ate proceeded via one-photon absorption processes for F-2 laser irradiation , but did not occur for ArF laser (6.4 eV) irradiation. This F-2-induced hy drogen-bonded state is distinguished from laser-induced compacted state bec ause the latter occurs for ArF or F-2 laser irradiations via two-photon abs orption processes. (C) 2001 American Institute of Physics.