The adsorption and thermal decomposition of digermane on Ge(111)

We have used multiple internal reflection infrared spectroscopy to investigate the interaction of digermane with Ge(111) at temperatures between 104–600 K. Digermane predominantly adsorbs molecularly on the surface below 120 K, displaying a vibrational spectrum similar to that of condensed digermane. At temperatures between 120–150 K, digermane dissociates via Ge–Ge bond scission to form adsorbed GeH3. Chemisorbed germyl GeH3 has a distinct symmetric deformation vibration at ∼772 cm−1, compared to a value of 721 cm−1 for molecularly adsorbed Ge2H6. At 200 K, Ge2H6 adsorption produces surface GeH3, GeH2, and GeH species with stretching vibrations at 2063, 2023, and 1968 cm−1, respectively. The surface GeH2 species is also identified by a characteristic scissor mode at ∼830 cm−1. Adsorption at 300 and 400 K produces only GeH2 and GeH, with a much lower concentration of GeH2 at 400 K. The surface GeH2 and GeH species are also generated by the successive decomposition of GeH3 upon heating. All surface hydrogen desorbs at ∼600 K.