Photoprocesses on the surface of nanoporous silicon

Photoprocesses on the surface of nanoporous silicon have been investigated by means of laser photodesorption mass spectrometry and laser-induced lumin escence. It is demonstrated for the first time that nonequilibrium photodes orption of silicon and molecular hydrogen occurs within the range of laser radiation intensities from 2 x 10(6) to 7 x 10(6) W/cm(2). At high laser in tensities, desorption occurs in a thermal regime and is due to the heating of the surface by a laser pulse. The competition between thermal and photos timulated desorption is analyzed. We propose a mechanism of photodesorption implying that the excitation of electrons in nanocrystallites is accompani ed by the saturation of upper energy states. Under conditions of high conce ntration of excited electrons in nanocrystallites, electrons are efficientl y localized on free orbitals of Si-H-x surface complexes, which loosens or breaks complex-surface bonds under definite conditions.