The products of SiH4 decomposition on the surface of various filaments were directly detected by using vacuum ultraviolet (VUV) photo-ionization mass spectrometry under collision-free conditions. SiH2, and SiH3, were detected at filament temperatures of approximately T-f similar to 1300 K, where silicide formation on the filament was observed. At higher temperatures, the SiH2, and SiH3 signal intensities decreased and Si atom signal increased. It was confirmed that the Si atoms were the main species desorbed from the tungsten filament at T-f > 1700 K. H atoms were also detected as a direct desorbed species from the filament by using the [2 + 1] resonance enhanced multi-photon ionization (REMPI) method combined with time-of-flight (TOF) mass spectrometry. Gas phase chemical reactions of SiH4, with desorbed radicals (Si and H atoms) were also investigated. Si2H6, Si2H4 and Si-2 could be detected as products of gas phase reactions. A chemical kinetic mechanism starting with Si + SiH4 and H + SiH4 reactions was proposed to explain the formation of Si2H6 and Si2H4. 2001 Elsevier Science B.V. All rights reserved.