Adsorption and Thermal Reaction of Short-Chain Iodoalkanes on Ge(100)

The adsorption and thermal decomposition of iodoalkanes CH3I, C2H5I, and C4H9I on Ge(100) were studied with temperature-programmed desorption (TPD) and X-ray photoelectron Spectra (XPS) using synchrotron radiation. At 105 K, the iodoalkanes adsorb both molecularly and dissociatively on Ge(100) the shorter-chain iodoalkane dissociates to form a surface alkyl and ail I adatom to a greater extent. The chemisorbed iodoalkane gradually dissociates to form a surface alkyl and ail I adatom in a temperature range 200-370 K. At 720 K, most Surface CH3 desorbs directly from the surface, and other surface CH3 radicals undergo disproportionation to desorb as CH4, Surface C2H5 and C4H9 mostly undergo beta-hydride elimination to desorb as C2H4 and C4H8 at similar to 550 K, respectively. The temperature for C4H9 to react is slightly lower than that for C2H5 because the C4H9 chain exhibits a stronger interaction with the surface than C2H5. The I adatom can react with a H atom liberated during decomposition of a surface alkyl and Subsequently desorbs as molecular HI in two temperature regimes, similar to 650 and similar to 720 K. Sonic I adatoms are removed from the Surface via direct desorption in atomic form at 720 K. On annealing to 770 K, the Ge surface becomes free of I adatom but retains a deposit of residual C as adatoms. According to our data, the temperature of fabrication and operation of a Ge-based device with the alkyl monolayer is suggested to be not higher than 530 K.